Atmel 8-bit AVR Microcontroller with 512/1024 Bytes In-System
Programmable Flash
ATtiny4 / ATtiny5 / ATtiny9 / ATtiny10
DATASHEET COMPLETE
Introduction
The Atmel® ATtiny4/5/9/10 is a low-power CMOS 8-bit microcontroller based
on the AVR® enhanced RISC architecture. By executing powerful
instructions in a single clock cycle, the ATtiny4/5/9/10 achieves throughputs
close to 1 MIPS per MHz. This empowers system designer to optimize the
device for power consumption versus processing speed.
Feature
•High Performance, Low Power AVR® 8-Bit Microcontroller
•Advanced RISC Architecture
–54 Powerful Instructions
–Most Single Clock Cycle Execution
–16 x 8 General Purpose Working Registers
–Fully Static Operation
–Up to 12 MIPS Throughput at 12 MHz
•Non-volatile Program and Data Memories
–512/1024 Bytes of In-System Programmable Flash Program
Memory
–32 Bytes Internal SRAM
–Flash Write/Erase Cycles: 10,000
–Data Retention: 20 Years at 85°C / 100 Years at 25°C
•Peripheral Features
–QTouch® Library Support for Capacitive Touch Sensing (1
Channel)
–One 16-bit Timer/Counter with Prescaler and Two PWM
Channels
–Programmable Watchdog Timer with Separate On-chip Oscillator
–4-channel, 8-bit Analog to Digital Converter (ATtiny5/10, only)
–On-chip Analog Comparator
•Special Microcontroller Features
–In-System Programmable (at 5V, only)
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–External and Internal Interrupt Sources
–Low Power Idle, ADC Noise Reduction, and Power-down Modes
–Enhanced Power-on Reset Circuit
–Programmable Supply Voltage Level Monitor with Interrupt and Reset
–Internal Calibrated Oscillator
•I/O and Packages
–Four Programmable I/O Lines
–6-pin SOT and 8-pad UDFN
•Operating Voltage:
–1.8 - 5.5V
•Programming Voltage:
–5V
•Speed Grade:
–0 - 4 MHz @ 1.8 - 5.5V
–0 - 8 MHz @ 2.7 - 5.5V
–0 - 12 MHz @ 4.5 - 5.5V
•Industrial and Extended Temperature Ranges
•Low Power Consumption
–Active Mode:
• 200μA at 1MHz and 1.8V
Idle Mode:
• 25μA at 1MHz and 1.8V
–Power-down Mode:
• <0.1μA at 1.8V
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Table of Contents
Introduction......................................................................................................................1
Feature............................................................................................................................ 1
1. Pin Configurations..................................................................................................... 7
1.1. Pin Descriptions............................................................................................................................7
2. Ordering Information..................................................................................................9
2.1. ATtiny4..........................................................................................................................................9
2.2. ATtiny5..........................................................................................................................................9
2.3. ATtiny9........................................................................................................................................10
2.4. ATtiny10......................................................................................................................................11
3. Overview..................................................................................................................12
3.1. Block Diagram............................................................................................................................ 12
3.2. Comparison of ATtiny4, ATtiny5, ATtiny9 and ATtiny10............................................................. 13
4. General Information.................................................................................................14
4.1. Resources.................................................................................................................................. 14
4.2. Data Retention............................................................................................................................14
4.3. About Code Examples................................................................................................................14
4.4. Capacitive Touch Sensing.......................................................................................................... 14
5. AVR CPU Core........................................................................................................ 15
5.1. Overview.....................................................................................................................................15
5.2. ALU – Arithmetic Logic Unit........................................................................................................16
5.3. Status Register...........................................................................................................................16
5.4. General Purpose Register File................................................................................................... 17
5.5. The X-register, Y-register, and Z-register................................................................................... 17
5.6. Stack Pointer.............................................................................................................................. 18
5.7. Instruction Execution Timing...................................................................................................... 18
5.8. Reset and Interrupt Handling..................................................................................................... 19
5.9. Register Description................................................................................................................... 20
6. AVR Memories.........................................................................................................25
6.1. Overview.....................................................................................................................................25
6.2. In-System Reprogrammable Flash Program Memory................................................................25
6.3. SRAM Data Memory...................................................................................................................25
6.4. I/O Memory.................................................................................................................................27
7. AVR Memories.........................................................................................................28
7.1. Overview.....................................................................................................................................28
7.2. In-System Reprogrammable Flash Program Memory................................................................28
7.3. SRAM Data Memory...................................................................................................................28
7.4. I/O Memory.................................................................................................................................30
8. Clock System...........................................................................................................31
8.1. Clock Distribution........................................................................................................................31
8.2. Clock Subsystems......................................................................................................................31
8.3. Clock Sources............................................................................................................................ 32
8.4. System Clock Prescaler............................................................................................................. 33
8.5. Starting....................................................................................................................................... 34
8.6. Register Description................................................................................................................... 35
9. Power Management and Sleep Modes....................................................................40
9.1. Overview.....................................................................................................................................40
9.2. Sleep Modes...............................................................................................................................40
9.3. Power Reduction Register..........................................................................................................41
9.4. Minimizing Power Consumption................................................................................................. 42
9.5. Register Description................................................................................................................... 43
10. System Control and Reset.......................................................................................46
10.1. Resetting the AVR...................................................................................................................... 46
10.2. Reset Sources............................................................................................................................46
10.3. Watchdog Timer......................................................................................................................... 49
10.4. Register Description................................................................................................................... 51
11. Interrupts..................................................................................................................56
11.1. Overview.....................................................................................................................................56
11.2. Interrupt Vectors ........................................................................................................................ 56
11.3. External Interrupts...................................................................................................................... 57
11.4. Register Description................................................................................................................... 58
12. I/O-Ports.................................................................................................................. 65
12.1. Overview.....................................................................................................................................65
12.2. Ports as General Digital I/O........................................................................................................66
12.3. Register Description................................................................................................................... 75
13. 16-bit Timer/Counter0 with PWM.............................................................................81
13.1. Features..................................................................................................................................... 81
13.2. Overview.....................................................................................................................................81
13.3. Accessing 16-bit Registers.........................................................................................................83
13.4. Timer/Counter Clock Sources.................................................................................................... 86
13.5. Counter Unit............................................................................................................................... 87
13.6. Input Capture Unit...................................................................................................................... 89
13.7. Output Compare Units................................................................................................................90
13.8. Compare Match Output Unit.......................................................................................................92
13.9. Modes of Operation....................................................................................................................93
13.10. Timer/Counter Timing Diagrams.............................................................................................. 101
13.11. Register Description................................................................................................................. 102
14. Analog Comparator............................................................................................... 120
14.1. Overview...................................................................................................................................120
14.2. Register Description................................................................................................................. 120
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15. ADC - Analog to Digital Converter.........................................................................124
15.1. Features................................................................................................................................... 124
15.2. Overview...................................................................................................................................124
15.3. Starting a Conversion...............................................................................................................125
15.4. Prescaling and Conversion Timing...........................................................................................126
15.5. Changing Channel or Reference Selection.............................................................................. 128
15.6. ADC Input Channels.................................................................................................................129
15.7. ADC Voltage Reference........................................................................................................... 129
15.8. ADC Noise Canceler................................................................................................................ 129
15.9. Analog Input Circuitry............................................................................................................... 130
15.10. Analog Noise Canceling Techniques........................................................................................130
15.11. ADC Accuracy Definitions........................................................................................................ 131
15.12. ADC Conversion Result........................................................................................................... 132
15.13. Register Description.................................................................................................................133
16. Programming interface.......................................................................................... 140
16.1. Features................................................................................................................................... 140
16.2. Overview...................................................................................................................................140
16.3. Physical Layer of Tiny Programming Interface.........................................................................141
16.4. Instruction Set...........................................................................................................................145
16.5. Accessing the Non-Volatile Memory Controller........................................................................ 148
16.6. Control and Status Space Register Descriptions..................................................................... 148
17. MEMPROG- Memory Programming......................................................................152
17.1. Features................................................................................................................................... 152
17.2. Overview...................................................................................................................................152
17.3. Non-Volatile Memories (NVM)..................................................................................................153
17.4. Accessing the NVM.................................................................................................................. 156
17.5. Self programming..................................................................................................................... 159
17.6. External Programming..............................................................................................................159
17.7. Register Description................................................................................................................. 159
18. Electrical Characteristics....................................................................................... 162
18.1. Absolute Maximum Ratings*.................................................................................................... 162
18.2. DC Characteristics....................................................................................................................162
18.3. Speed....................................................................................................................................... 164
18.4. Clock Characteristics................................................................................................................164
18.5. System and Reset Characteristics........................................................................................... 165
18.6. Analog Comparator Characteristics..........................................................................................166
18.7. ADC Characteristics (ATtiny5/10, only).................................................................................... 167
18.8. Serial Programming Characteristics.........................................................................................167
19. Typical Characteristics...........................................................................................169
19.1. Supply Current of I/O Modules................................................................................................. 169
19.2. Active Supply Current...............................................................................................................170
19.3. Idle Supply Current...................................................................................................................173
19.4. Power-down Supply Current.....................................................................................................175
19.5. Pin Pull-up................................................................................................................................ 176
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19.6. Pin Driver Strength................................................................................................................... 179
19.7. Pin Threshold and Hysteresis...................................................................................................183
19.8. Analog Comparator Offset........................................................................................................187
19.9. Internal Oscillator Speed.......................................................................................................... 188
19.10. VLM Thresholds....................................................................................................................... 190
19.11. Current Consumption of Peripheral Units.................................................................................192
19.12. Current Consumption in Reset and Reset Pulsewidth............................................................. 195
20. Register Summary.................................................................................................196
20.1. Note..........................................................................................................................................197
21. Instruction Set Summary....................................................................................... 198
22. Packaging Information...........................................................................................202
22.1. 6ST1.........................................................................................................................................202
22.2. 8MA4........................................................................................................................................ 203
23. Errata.....................................................................................................................204
23.1. ATtiny4......................................................................................................................................204
23.2. ATtiny5......................................................................................................................................204
23.3. ATtiny9......................................................................................................................................205
23.4. ATtiny10....................................................................................................................................206
24. Datasheet Revision History................................................................................... 207
24.1. Rev. 8127F – 02/13.................................................................................................................. 207
24.2. Rev. 8127E – 11/11.................................................................................................................. 207
24.3. Rev. 8127D – 02/10..................................................................................................................207
24.4. Rev. 8127C – 10/09..................................................................................................................207
24.5. Rev. 8127B – 08/09.................................................................................................................. 207
24.6. Rev. 8127A – 04/09.................................................................................................................. 208
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1. Pin Configurations
Figure 1-1 Pinout of ATtiny4/5/9/10
1
2
3 4
6
5 VCC
GND
PB2 (T0/CLKO/PCINT2/INT0/ADC2)
PB3 (RESET/PCINT3/ADC3)
SOT-23
(PCINT0/TPIDATA /OC0A/ADC0/AIN0) PB0
(PCINT1/TPICLK/CLKI/ICP0/OC0B/ADC1/AIN1) PB1
1
2
3
4
8
7
6
5
VCC
GND
PB3 (RESET/PCINT3/ADC3)
PB0 (AIN0/ADC0/OC0A/TPIDATA /PCINT0)
Power
Clock
Digital
GND
Analog
UDFN
PB2 (T0/CLKO/PCINT2/INT0/ADC2)(PCINT1/TPICLK/CLKI/ICP0/OC0B/ADC1/AIN1) PB1
NC
NC
NC
1.1. Pin Descriptions
1.1.1. VCC
Digital supply voltage.
1.1.2. GND
Ground.
1.1.3. Port B (PB[3:0])
This is a 4-bit, bi-directional I/O port with internal pull-up resistors, individually selectable for each bit. The
output buffers have symmetrical drive characteristics, with both high sink and source capability. As inputs,
the port pins that are externally pulled low will source current if pull-up resistors are activated. Port pins
are tri-stated when a reset condition becomes active, even if the clock is not running.
1.1.4. RESET
Reset input. A low level on this pin for longer than the minimum pulse length will generate a reset, even if
the clock is not running and provided the reset pin has not been disabled. The minimum pulse length is
given in System and Reset Characteristics of Electrical Characteristics. Shorter pulses are not
guaranteed to generate a reset.
The reset pin can also be used as a (weak) I/O pin.
Related Links
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2. Ordering Information
2.1. ATtiny4
Supply Voltage Speed (1) Temperature Package (2) Ordering Code (3)
1.8 – 5.5V 12 MHz Industrial
(-40°C to 85°C) (4)
6ST1 ATtiny4-TSHR(5)
8MA4 ATtiny4-MAHR (6)
10 MHz Extended
(-40°C to 125°C) (6)
6ST1 ATtiny4-TS8R (5)
Note:
1. For speed vs. supply voltage, see section Speed.
2. All packages are Pb-free, halide-free and fully green and they comply with the European directive
for Restriction of Hazardous Substances (RoHS). NiPdAu finish.
3. Tape and reel.
4. Can also be supplied in wafer form. Contact your local Atmel sales office for ordering information
and minimum quantities.
5. Top/bottomside markings:
–Top: T4x, where x = die revision
–Bottom: zHzzz or z8zzz, where H = (-40°C to 85°C), and 8 = (-40°C to 125°C)
6. For typical and Electrical characteristics for this device please consult Appendix A, ATtiny4/5/9/10
Specification at 125°C.
Table 2-1 Package Type
6ST1 6-lead, 2.90 x 1.60 mm Plastic Small Outline Package (SOT23)
8MA4 8-pad, 2 x 2 x 0.6 mm Plastic Ultra Thin Dual Flat No Lead (UDFN)
Related Links
Speed on page 164
2.2. ATtiny5
Supply Voltage Speed (1) Temperature Package (2) Ordering Code (3)
1.8 – 5.5V 12 MHz Industrial
(-40°C to 85°C) (4)
6ST1 ATtiny5-TSHR(5)
8MA4 ATtiny5-MAHR (6)
10 MHz Extended
(-40°C to 125°C) (6)
6ST1 ATtiny5-TS8R (5)
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Note:
1. For speed vs. supply voltage, see section Speed.
2. All packages are Pb-free, halide-free and fully green and they comply with the European directive
for Restriction of Hazardous Substances (RoHS). NiPdAu finish.
3. Tape and reel.
4. Can also be supplied in wafer form. Contact your local Atmel sales office for ordering information
and minimum quantities.
5. Top/bottomside markings:
–Top: T5x, where x = die revision
–Bottom: zHzzz or z8zzz, where H = (-40°C to 85°C), and 8 = (-40°C to 125°C)
6. For typical and Electrical characteristics for this device please consult Appendix A, ATtiny4/5/9/10
Specification at 125°C.
Table 2-2 Package Type
6ST1 6-lead, 2.90 x 1.60 mm Plastic Small Outline Package (SOT23)
8MA4 8-pad, 2 x 2 x 0.6 mm Plastic Ultra Thin Dual Flat No Lead (UDFN)
Related Links
Speed on page 164
2.3. ATtiny9
Supply Voltage Speed (1) Temperature Package (2) Ordering Code (3)
1.8 – 5.5V 12 MHz Industrial
(-40°C to 85°C) (4)
6ST1 ATtiny9-TSHR(5)
8MA4 ATtiny9-MAHR (6)
10 MHz Extended
(-40°C to 125°C) (6)
6ST1 ATtiny9-TS8R (5)
Note:
1. For speed vs. supply voltage, see section Speed.
2. All packages are Pb-free, halide-free and fully green and they comply with the European directive
for Restriction of Hazardous Substances (RoHS). NiPdAu finish.
3. Tape and reel.
4. Can also be supplied in wafer form. Contact your local Atmel sales office for ordering information
and minimum quantities.
5. Top/bottomside markings:
–Top: T9x, where x = die revision
–Bottom: zHzzz or z8zzz, where H = (-40°C to 85°C), and 8 = (-40°C to 125°C)
6. For typical and Electrical characteristics for this device please consult Appendix A, ATtiny4/5/9/10
Specification at 125°C.
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Table 2-3 Package Type
6ST1 6-lead, 2.90 x 1.60 mm Plastic Small Outline Package (SOT23)
8MA4 8-pad, 2 x 2 x 0.6 mm Plastic Ultra Thin Dual Flat No Lead (UDFN)
Related Links
Speed on page 164
2.4. ATtiny10
Supply Voltage Speed (1) Temperature Package (2) Ordering Code (3)
1.8 – 5.5V 12 MHz Industrial
(-40°C to 85°C) (4)
6ST1 ATtiny10-TSHR(5)
8MA4 ATtiny10-MAHR (6)
10 MHz Extended
(-40°C to 125°C) (6)
6ST1 ATtiny10-TS8R (5)
Note:
1. For speed vs. supply voltage, see section Speed.
2. All packages are Pb-free, halide-free and fully green and they comply with the European directive
for Restriction of Hazardous Substances (RoHS). NiPdAu finish.
3. Tape and reel.
4. Can also be supplied in wafer form. Contact your local Atmel sales office for ordering information
and minimum quantities.
5. Top/bottomside markings:
–Top: T10x, where x = die revision
–Bottom: zHzzz or z8zzz, where H = (-40°C to 85°C), and 8 = (-40°C to 125°C)
6. For typical and Electrical characteristics for this device please consult Appendix A, ATtiny4/5/9/10
Specification at 125°C.
Table 2-4 Package Type
6ST1 6-lead, 2.90 x 1.60 mm Plastic Small Outline Package (SOT23)
8MA4 8-pad, 2 x 2 x 0.6 mm Plastic Ultra Thin Dual Flat No Lead (UDFN)
Related Links
Speed on page 164
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3. Overview
This device is low-power CMOS 8-bit microcontrollers based on the compact AVR enhanced RISC
architecture. By executing powerful instructions in a single clock cycle, the device achieve throughputs
approaching 1 MIPS per MHz, allowing the system designer to optimize power consumption versus
processing speed.
3.1. Block Diagram
Figure 3-1 Block Diagram
CPU
ADC[7:0]
Vcc
I/O
PORTS
D
A
T
A
B
U
S
SRAM
FLASH
AC
AIN0
AIN1
ACO
ADCMUX
Watchdog
Timer
Power
management
and clock
control
Vcc
GND
Power
Supervision
POR & RESET
RESET
PCINT[3:0]
INT0
Interrupt
Clock generation
128 kHz Internal Osc
External clock
8MHz Calib Osc
PB[3:0]
Internal
Reference
ADC
TC 0
(16-bit)
OC0A/B
T0
ICP0
3.1.1. Description
The AVR core combines a rich instruction set with 16 general purpose working registers and system
registers. All registers are directly connected to the Arithmetic Logic Unit (ALU), allowing two independent
registers to be accessed in one single instruction executed in one clock cycle. The resulting architecture
is compact and code efficient while achieving throughputs up to ten times faster than conventional CISC
microcontrollers.
This device provides the following features: 512/1024 byte of In-System Programmable Flash, 32 bytes of
SRAM, four general purpose I/O lines, 16 general purpose working registers, a 16-bit timer/counter with
two PWM channels, internal and external interrupts, a programmable watchdog timer with internal
oscillator, an internal calibrated oscillator, and four software selectable power saving modes. ATtiny5/10
are also equipped with a four-channel and 8-bit Analog to Digital Converter (ADC).
Idle mode stops the CPU while allowing the SRAM, timer/counter, ADC (ATtiny5/10, only), analog
comparator, and interrupt system to continue functioning. ADC Noise Reduction mode minimizes
switching noise during ADC conversions by stopping the CPU and all I/O modules except the ADC. In
Power-down mode registers keep their contents and all chip functions are disabled until the next interrupt
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or hardware reset. In Standby mode, the oscillator is running while the rest of the device is sleeping,
allowing very fast start-up combined with low power consumption.
The device is manufactured using Atmel’s high density Non-Volatile Memory (NVM) technology. The on-
chip, in-system programmable Flash allows program memory to be re-programmed in-system by a
conventional, non-volatile memory programmer.
The ATtiny4/5/9/10AVR are supported by a suite of program and system development tools, including
macro assemblers and evaluation kits.
3.2. Comparison of ATtiny4, ATtiny5, ATtiny9 and ATtiny10
A comparison of the devices is shown in the table below.
Table 3-1 Differences between ATtiny4, ATtiny5, ATtiny9 and ATtiny10
Device Flash ADC Signature
ATtiny4 512 bytes No 0x1E 0x8F 0x0A
ATtiny5 512 bytes Yes 0x1E 0x8F 0x09
ATtiny9 1024 bytes No 0x1E 0x90 0x08
ATtiny10 1024 bytes Yes 0x1E 0x90 0x03
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4. General Information
4.1. Resources
A comprehensive set of development tools, application notes and datasheets are available for download
on http://www.atmel.com/avr.
4.2. Data Retention
Reliability Qualification results show that the projected data retention failure rate is much less than 1 PPM
over 20 years at 85°C or 100 years at 25°C.
4.3. About Code Examples
This documentation contains simple code examples that briefly show how to use various parts of the
device. These code examples assume that the part specific header file is included before compilation. Be
aware that not all C compiler vendors include bit definitions in the header files and interrupt handling in C
is compiler dependent. Confirm with the C compiler documentation for more details.
4.4. Capacitive Touch Sensing
4.4.1. QTouch Library
The Atmel® QTouch® Library provides a simple to use solution to realize touch sensitive interfaces on
most Atmel AVR® microcontrollers. The QTouch Library includes support for the Atmel QTouch and Atmel
QMatrix® acquisition methods.
Touch sensing can be added to any application by linking the appropriate Atmel QTouch Library for the
AVR Microcontroller. This is done by using a simple set of APIs to define the touch channels and sensors,
and then calling the touch sensing API’s to retrieve the channel information and determine the touch
sensor states.
The QTouch Library is FREE and downloadable from the Atmel website at the following location: http://
www.atmel.com/technologies/touch/. For implementation details and other information, refer to the Atmel
QTouch Library User Guide - also available for download from the Atmel website.
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5. AVR CPU Core
5.1. Overview
This section discusses the AVR core architecture in general. The main function of the CPU core is to
ensure correct program execution. The CPU must therefore be able to access memories, perform
calculations, control peripherals, and handle interrupts.
Figure 5-1 Block Diagram of the AVR Architecture
Flas h
Program
Memory
Instruction
Re gis ter
Instruction
Decoder
Program
Counter
Control Lines
16 x 8
Ge ne ra l
Purpos e
Re gis trers
ALU
Status
and Control
I/O Lines
Data Bus 8-bit
Data
SRAM
Direct Addres s ing
Indirect Addres s ing
Inte rrupt
Unit
Wa tchdog
Timer
Analog
Comparator
Timer/Counter 0
ADC
In order to maximize performance and parallelism, the AVR uses a Harvard architecture – with separate
memories and buses for program and data. Instructions in the program memory are executed with a
single level pipelining. While one instruction is being executed, the next instruction is pre-fetched from the
program memory. This concept enables instructions to be executed in every clock cycle. The program
memory is In-System Reprogrammable Flash memory.
The fast-access Register File contains 16 x 8-bit general purpose working registers with a single clock
cycle access time. This allows single-cycle Arithmetic Logic Unit (ALU) operation. In a typical ALU
operation, two operands are output from the Register File, the operation is executed, and the result is
stored back in the Register File – in one clock cycle.
Six of the 16 registers can be used as three 16-bit indirect address register pointers for Data Space
addressing – enabling efficient address calculations. One of the these address pointers can also be used
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as an address pointer for look up tables in Flash program memory. These added function registers are
the 16-bit X-, Y-, and Z-register, described later in this section.
The ALU supports arithmetic and logic operations between registers or between a constant and a
register. Single register operations can also be executed in the ALU. After an arithmetic operation, the
Status Register is updated to reflect information about the result of the operation.
Program flow is provided by conditional and unconditional jump and call instructions, able to directly
address the whole address space. Most AVR instructions have a single 16-bit word format but 32-bit wide
instructions also exist. The actual instruction set varies, as some devices only implement a part of the
instruction set.
During interrupts and subroutine calls, the return address Program Counter (PC) is stored on the Stack.
The Stack is effectively allocated in the general data SRAM, and consequently the Stack size is only
limited by the total SRAM size and the usage of the SRAM. All user programs must initialize the SP in the
Reset routine (before subroutines or interrupts are executed). The Stack Pointer (SP) is read/write
accessible in the I/O space. The data SRAM can easily be accessed through the four different addressing
modes supported in the AVR architecture.
The memory spaces in the AVR architecture are all linear and regular memory maps.
A flexible interrupt module has its control registers in the I/O space with an additional Global Interrupt
Enable bit in the Status Register. All interrupts have a separate Interrupt Vector in the Interrupt Vector
table. The interrupts have priority in accordance with their Interrupt Vector position. The lower the
Interrupt Vector address, the higher the priority.
The I/O memory space contains 64 addresses for CPU peripheral functions as Control Registers, SPI,
and other I/O functions. The I/O memory can be accessed as the data space locations, 0x0000 - 0x003F.
5.2. ALU – Arithmetic Logic Unit
The high-performance AVR ALU operates in direct connection with all the 16 general purpose working
registers. Within a single clock cycle, arithmetic operations between general purpose registers or between
a register and an immediate are executed. The ALU operations are divided into three main categories –
arithmetic, logical, and bit-functions. Some implementations of the architecture also provide a powerful
multiplier supporting both signed/unsigned multiplication and fractional format. See Instruction Set
Summary section for a detailed description.
Related Links
Instruction Set Summary on page 198
5.3. Status Register
The Status Register contains information about the result of the most recently executed arithmetic
instruction. This information can be used for altering program flow in order to perform conditional
operations. The Status Register is updated after all ALU operations, as specified in the Instruction Set
Reference. This will in many cases remove the need for using the dedicated compare instructions,
resulting in faster and more compact code.
The Status Register is not automatically stored when entering an interrupt routine and restored when
returning from an interrupt. This must be handled by software.
Related Links
Instruction Set Summary on page 198
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5.4. General Purpose Register File
The Register File is optimized for the AVR Enhanced RISC instruction set. In order to achieve the
required performance and flexibility, the following input/output schemes are supported by the Register
File:
•One 8-bit output operand and one 8-bit result input
•Two 8-bit output operands and one 8-bit result input
•One 16-bit output operand and one 16-bit result input
Figure 5-2 AVR CPU General Purpose Working Registers
7 0
R16
R17
General R18
Purpose …
Working R26 X-register Low Byte
Registers R27 X-register High Byte
R28 Y-register Low Byte
R29 Y-register High Byte
R30 Z-register Low Byte
R31 Z-register High Byte
Note: A typical implementation of the AVR register file includes 32 general purpose registers but
ATtiny4/5/9/10 implement only 16 registers. For reasons of compatibility the registers are numbered
R16...R31, not R0...R15.
Most of the instructions operating on the Register File have direct access to all registers, and most of
them are single cycle instructions.
5.5. The X-register, Y-register, and Z-register
The registers R26...R31 have some added functions to their general purpose usage. These registers are
16-bit address pointers for indirect addressing of the data space. The three indirect address registers X,
Y, and Z are defined as described in the figure.
Figure 5-3 The X-, Y-, and Z-registers
15
XH
XL
0
X-re gis te r
7
0
7
0
R27
R26
15
YH
YL
0
Y-re gis te r
7
0
7
0
R29
R28
15
ZH
ZL
0
Z-re gis te r
7
0
7
0
R31
R30
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In the different addressing modes these address registers have functions as fixed displacement,
automatic increment, and automatic decrement. See Instruction Set Summary for details.
Related Links
Instruction Set Summary on page 198
5.6. Stack Pointer
The Stack is mainly used for storing temporary data, for storing local variables and for storing return
addresses after interrupts and subroutine calls. The Stack is implemented as growing from higher to
lower memory locations. The Stack Pointer Register always points to the top of the Stack, and the Stack
Pointer must be set to point above 0x40.
The Stack Pointer points to the data SRAM Stack area where the Subroutine and Interrupt Stacks are
located. A Stack PUSH command will decrease the Stack Pointer. The Stack in the data SRAM must be
defined by the program before any subroutine calls are executed or interrupts are enabled. Initial Stack
Pointer value equals the last address of the internal SRAM and the Stack Pointer must be set to point
above start of the SRAM. See the table for Stack Pointer details.
Table 5-1 Stack Pointer Instructions
Instruction Stack pointer Description
PUSH Decremented by 1 Data is pushed onto the stack
ICALL
RCALL
Decremented by 2 Return address is pushed onto the stack with a subroutine call or
interrupt
POP Incremented by 1 Data is popped from the stack
RET
RETI
Incremented by 2 Return address is popped from the stack with return from subroutine or
return from interrupt
The AVR Stack Pointer is implemented as two 8-bit registers in the I/O space. The number of bits actually
used is implementation dependent. Note that the data space in some implementations of the AVR
architecture is so small that only SPL is needed. In this case, the SPH Register will not be present.
5.7. Instruction Execution Timing
This section describes the general access timing concepts for instruction execution. The AVR CPU is
driven by the CPU clock clkCPU, directly generated from the selected clock source for the chip. No internal
clock division is used. The Figure below shows the parallel instruction fetches and instruction executions
enabled by the Harvard architecture and the fast-access Register File concept. This is the basic pipelining
concept to obtain up to 1 MIPS per MHz with the corresponding unique results for functions per cost,
functions per clocks, and functions per power-unit.
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Figure 5-4 The Parallel Instruction Fetches and Instruction Executions
clk
1st Instruction Fetch
1st Instruction Execute
2nd Instruction Fetch
2nd Instruction Execute
3rd Instruction Fetch
3rd Instruction Execute
4th Instruction Fetch
T1 T2 T3 T4
CPU
The following Figure shows the internal timing concept for the Register File. In a single clock cycle an
ALU operation using two register operands is executed, and the result is stored back to the destination
register.
Figure 5-5 Single Cycle ALU Operation
Total Execution Time
Register Operands Fetch
ALU Operation Execute
Result Write Back
T1 T2 T3 T4
clkCPU
5.8. Reset and Interrupt Handling
The AVR provides several different interrupt sources. These interrupts and the separate Reset Vector
each have a separate program vector in the program memory space. All interrupts are assigned individual
enable bits which must be written logic one together with the Global Interrupt Enable bit in the Status
Register in order to enable the interrupt.
The lowest addresses in the program memory space are by default defined as the Reset and Interrupt
Vectors. The complete list of vectors is shown in Interrupts. They have determined priority levels: The
lower the address the higher is the priority level. RESET has the highest priority, and next is INT0 – the
External Interrupt Request 0.
When an interrupt occurs, the Global Interrupt Enable I-bit is cleared and all interrupts are disabled. The
user software can write logic one to the I-bit to enable nested interrupts. All enabled interrupts can then
interrupt the current interrupt routine. The I-bit is automatically set when a Return from Interrupt
instruction – RETI – is executed.
There are basically two types of interrupts:
•The first type is triggered by an event that sets the Interrupt Flag. For these interrupts, the Program
Counter is vectored to the actual Interrupt Vector in order to execute the interrupt handling routine,
and hardware clears the corresponding Interrupt Flag. Interrupt Flags can also be cleared by writing
a logic one to the flag bit position(s) to be cleared. If an interrupt condition occurs while the
corresponding interrupt enable bit is cleared, the Interrupt Flag will be set and remembered until the
interrupt is enabled, or the flag is cleared by software. Similarly, if one or more interrupt conditions
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occur while the Global Interrupt Enable bit is cleared, the corresponding Interrupt Flag(s) will be set
and remembered until the Global Interrupt Enable bit is set, and will then be executed by order of
priority.
•The second type of interrupts will trigger as long as the interrupt condition is present. These
interrupts do not necessarily have Interrupt Flags. If the interrupt condition disappears before the
interrupt is enabled, the interrupt will not be triggered.
When the AVR exits from an interrupt, it will always return to the main program and execute one more
instruction before any pending interrupt is served.
The Status Register is not automatically stored when entering an interrupt routine, nor restored when
returning from an interrupt routine. This must be handled by software.
When using the CLI instruction to disable interrupts, the interrupts will be immediately disabled. No
interrupt will be executed after the CLI instruction, even if it occurs simultaneously with the CLI instruction.
When using the SEI instruction to enable interrupts, the instruction following SEI will be executed before
any pending interrupts, as shown in this example.
Assembly Code Example
sei ; set Global Interrupt Enable
sleep ; enter sleep, waiting for interrupt
; note: will enter sleep before any pending interrupt(s)
Note: See Code Examples
Related Links
Interrupts on page 56
About Code Examples on page 14
5.8.1. Interrupt Response Time
The interrupt execution response for all the enabled AVR interrupts is four clock cycles minimum. After
four clock cycles the program vector address for the actual interrupt handling routine is executed. During
this four clock cycle period, the Program Counter is pushed onto the Stack. The vector is normally a jump
to the interrupt routine, and this jump takes three clock cycles. If an interrupt occurs during execution of a
multi-cycle instruction, this instruction is completed before the interrupt is served. If an interrupt occurs
when the MCU is in sleep mode, the interrupt execution response time is increased by four clock cycles.
This increase comes in addition to the start-up time from the selected sleep mode. A return from an
interrupt handling routine takes four clock cycles. During these four clock cycles, the Program Counter
(two bytes) is popped back from the Stack, the Stack Pointer is incremented by two, and the I-bit in SREG
is set.
5.9. Register Description
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5.9.1. Configuration Change Protection Register
Name: CCP
Offset: 0x3C
Reset: 0x00
Property:
-
Bit 7 6 5 4 3 2 1 0
CCP[7:0]
Access
Reset 0 0 0 0 0 0 0 0
Bits 7:0 – CCP[7:0]: Configuration Change Protection
In order to change the contents of a protected I/O register the CCP register must first be written with the
correct signature. After CCP is written the protected I/O registers may be written to during the next four
CPU instruction cycles. All interrupts are ignored during these cycles. After these cycles interrupts are
automatically handled again by the CPU, and any pending interrupts will be executed according to their
priority.
When the protected I/O register signature is written, CCP[0] will read as one as long as the protected
feature is enabled, while CCP[7:1] will always read as zero.
CCP[7:1] only have write access. CCP[0] has both read and write access.
Table 5-2 Signatures Recognized by the Configuration Change Protection Register
Signature Group Description
0xD8 IOREG: CLKMSR, CLKPSR, WDTCSR Protected I/O register
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5.9.2. Stack Pointer Register High byte
Name: SPH
Offset: 0x3E
Reset: RAMEND
Property:
-
Bit 7 6 5 4 3 2 1 0
(SP[15:8]) SPH[7:0]
Access RW RW RW RW RW RW RW RW
Reset
Bits 7:0 – (SP[15:8]) SPH[7:0]: Stack Pointer Register
SPL and SPH are combined into SP. It means SPH[7:0] is SP[15:8].
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5.9.3. Stack Pointer Register Low byte
Name: SPL
Offset: 0x3D
Reset: RAMEND
Property:
-
Bit 7 6 5 4 3 2 1 0
(SP[7:0]) SPL[7:0]
Access RW RW RW RW RW RW RW RW
Reset
Bits 7:0 – (SP[7:0]) SPL[7:0]: Stack Pointer Register
SPL and SPH are combined into SP. It means SPL[7:0] is SP[7:0].
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5.9.4. Status Register
Name: SREG
Offset: 0x3F
Reset: 0x00
Property:
-
Bit 7 6 5 4 3 2 1 0
I T H S V N Z C
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 7 – I: Global Interrupt Enable
The Global Interrupt Enable bit must be set for the interrupts to be enabled. The individual interrupt
enable control is then performed in separate control registers. If the Global Interrupt Enable Register is
cleared, none of the interrupts are enabled independent of the individual interrupt enable settings. The I-
bit is cleared by hardware after an interrupt has occurred, and is set by the RETI instruction to enable
subsequent interrupts. The I-bit can also be set and cleared by the application with the SEI and CLI
instructions, as described in the instruction set reference.
Bit 6 – T: Copy Storage
The Bit Copy instructions BLD (Bit LoaD) and BST (Bit STore) use the T-bit as source or destination for
the operated bit. A bit from a register in the Register File can be copied into T by the BST instruction, and
a bit in T can be copied into a bit in a register in the Register File by the BLD instruction.
Bit 5 – H: Half Carry Flag
The Half Carry Flag H indicates a Half Carry in some arithmetic operations. Half Carry Flag is useful in
BCD arithmetic. See the Instruction Set Description for detailed information.
Bit 4 – S: Sign Flag, S = N ㊉ V
The S-bit is always an exclusive or between the Negative Flag N and the Two’s Complement Overflow
Flag V. See the Instruction Set Description for detailed information.
Bit 3 – V: Two’s Complement Overflow Flag
The Two’s Complement Overflow Flag V supports two’s complement arithmetic. See the Instruction Set
Description for detailed information.
Bit 2 – N: Negative Flag
The Negative Flag N indicates a negative result in an arithmetic or logic operation. See the Instruction Set
Description for detailed information.
Bit 1 – Z: Zero Flag
The Zero Flag Z indicates a zero result in an arithmetic or logic operation. See the Instruction Set
Description for detailed information.
Bit 0 – C: Carry Flag
The Carry Flag C indicates a carry in an arithmetic or logic operation. See the Instruction Set Description
for detailed information.
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6. AVR Memories
6.1. Overview
This section describes the different memory types in the device. The AVR architecture has two main
memory spaces, the Data Memory and the Program Memory space. All memory spaces are linear and
regular.
6.2. In-System Reprogrammable Flash Program Memory
The ATtiny4/5/9/10 contains 512/1024 bytes On-chip In-System Reprogrammable Flash memory for
program storage. Since all AVR instructions are 16 or 32 bits wide, the Flash is organized as 256/512 x
16.
The Flash memory has an endurance of at least 10,000 write/erase cycles. The device Program Counter
(PC) is 9 bits wide, thus addressing the 256/512 program memory locations, starting at 0x000. Memory
Programming contains a detailed description on Flash data serial downloading.
Constant tables can be allocated within the entire address space of program memory by using load/store
instructions. Since program memory can not be accessed directly, it has been mapped to the data
memory. The mapped program memory begins at byte address 0x4000 in data memory. Although
programs are executed starting from address 0x000 in program memory it must be addressed starting
from 0x4000 when accessed via the data memory.
Internal write operations to Flash program memory have been disabled and program memory therefore
appears to firmware as read-only. Flash memory can still be written to externally but internal write
operations to the program memory area will not be successful.
Timing diagrams of instruction fetch and execution are presented in Instruction Execution Timing section.
Related Links
MEMPROG- Memory Programming on page 152
Instruction Execution Timing on page 18
MEMPROG- Memory Programming on page 152
Instruction Execution Timing on page 18
6.3. SRAM Data Memory
Data memory locations include the I/O memory, the internal SRAM memory, the Non-Volatile Memory
(NVM) Lock bits, and the Flash memory. The following figure shows how the ATtiny4/5/9/10 SRAM
Memory is organized.
The first 64 locations are reserved for I/O memory, while the following 32 data memory locations address
the internal data SRAM.
The Non-Volatile Memory (NVM) Lock bits and all the Flash memory sections are mapped to the data
memory space. These locations appear as read-only for device firmware.
The four different addressing modes for data memory are direct, indirect, indirect with pre-decrement, and
indirect with post-increment. In the register file, registers R26 to R31 function as pointer registers for
indirect addressing.
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The IN and OUT instructions can access all 64 locations of I/O memory. Direct addressing using the LDS
and STS instructions reaches the 128 locations between 0x0040 and 0x00BF.
The indirect addressing reaches the entire data memory space. When using indirect addressing modes
with automatic pre-decrement and post-increment, the address registers X, Y, and Z are decremented or
incremented.
Figure 6-1 Data Memory Map (Byte Addressing)
0x0000 ... 0x003F
0x0040 ... 0x005F
0x0060 ... 0x3EFF
0x3F00 ... 0x3F01
0x3F02 ... 0x3F3F
0x3F40 ... 0x3F41
0x3F42 ... 0x3F7F
0x3F80 ... 0x3F81
0x3F82 ... 0x3FBF
0x3FC0 ... 0x3FC3
0x3FC4 ... 0x3FFF
0x4000 ... 0x41FF/0x43FF
0x4400 ... 0xFFFF
I/O SPACE
SRAM DATA MEMORY
(reserved)
NVM LOCK BITS
(reserved)
CONFIGURATION BITS
(reserved)
CALIBRATION BITS
(reserved)
DEVICE ID BITS
(reserved)
FLASH PROGRAM MEMORY
(reserved)
6.3.1. Data Memory Access Times
The internal data SRAM access is performed in two clkCPU cycles as described in the following Figure.
Figure 6-2 On-chip Data SRAM Access Cycles
clk
WR
RD
Data
Data
Address Address valid
T1 T2 T3
Compute Address
Read Write
CPU
Memory Access Instruction Next Instruction
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6.4. I/O Memory
The I/O space definition of the device is shown in the Register Summary.
All ATtiny4/5/9/10 I/Os and peripherals are placed in the I/O space. All I/O locations may be accessed by
the LD and ST instructions, transferring data between the 16 general purpose working registers and the
I/O space. I/O Registers within the address range 0x00-0x1F are directly bit-accessible using the SBI and
CBI instructions. In these registers, the value of single bits can be checked by using the SBIS and SBIC
instructions. Refer to the Instruction Set Summary section for more details.
For compatibility with future devices, reserved bits should be written to zero if accessed. Reserved I/O
memory addresses should never be written.
Some of the Status Flags are cleared by writing a '1' to them; this is described in the flag descriptions.
Note that, unlike most other AVRs, the CBI and SBI instructions will only operate on the specified bit, and
can therefore be used on registers containing such Status Flags. The CBI and SBI instructions work with
registers 0x00-0x1F only.
The I/O and Peripherals Control Registers are explained in later sections.
Related Links
Register Summary on page 196
Instruction Set Summary on page 198
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7. AVR Memories
7.1. Overview
This section describes the different memory types in the device. The AVR architecture has two main
memory spaces, the Data Memory and the Program Memory space. All memory spaces are linear and
regular.
7.2. In-System Reprogrammable Flash Program Memory
The ATtiny4/5/9/10 contains 512/1024 bytes On-chip In-System Reprogrammable Flash memory for
program storage. Since all AVR instructions are 16 or 32 bits wide, the Flash is organized as 256/512 x
16.
The Flash memory has an endurance of at least 10,000 write/erase cycles. The device Program Counter
(PC) is 9 bits wide, thus addressing the 256/512 program memory locations, starting at 0x000. Memory
Programming contains a detailed description on Flash data serial downloading.
Constant tables can be allocated within the entire address space of program memory by using load/store
instructions. Since program memory can not be accessed directly, it has been mapped to the data
memory. The mapped program memory begins at byte address 0x4000 in data memory. Although
programs are executed starting from address 0x000 in program memory it must be addressed starting
from 0x4000 when accessed via the data memory.
Internal write operations to Flash program memory have been disabled and program memory therefore
appears to firmware as read-only. Flash memory can still be written to externally but internal write
operations to the program memory area will not be successful.
Timing diagrams of instruction fetch and execution are presented in Instruction Execution Timing section.
Related Links
MEMPROG- Memory Programming on page 152
Instruction Execution Timing on page 18
MEMPROG- Memory Programming on page 152
Instruction Execution Timing on page 18
7.3. SRAM Data Memory
Data memory locations include the I/O memory, the internal SRAM memory, the Non-Volatile Memory
(NVM) Lock bits, and the Flash memory. The following figure shows how the ATtiny4/5/9/10 SRAM
Memory is organized.
The first 64 locations are reserved for I/O memory, while the following 32 data memory locations address
the internal data SRAM.
The Non-Volatile Memory (NVM) Lock bits and all the Flash memory sections are mapped to the data
memory space. These locations appear as read-only for device firmware.
The four different addressing modes for data memory are direct, indirect, indirect with pre-decrement, and
indirect with post-increment. In the register file, registers R26 to R31 function as pointer registers for
indirect addressing.
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The IN and OUT instructions can access all 64 locations of I/O memory. Direct addressing using the LDS
and STS instructions reaches the 128 locations between 0x0040 and 0x00BF.
The indirect addressing reaches the entire data memory space. When using indirect addressing modes
with automatic pre-decrement and post-increment, the address registers X, Y, and Z are decremented or
incremented.
Figure 7-1 Data Memory Map (Byte Addressing)
0x0000 ... 0x003F
0x0040 ... 0x005F
0x0060 ... 0x3EFF
0x3F00 ... 0x3F01
0x3F02 ... 0x3F3F
0x3F40 ... 0x3F41
0x3F42 ... 0x3F7F
0x3F80 ... 0x3F81
0x3F82 ... 0x3FBF
0x3FC0 ... 0x3FC3
0x3FC4 ... 0x3FFF
0x4000 ... 0x41FF/0x43FF
0x4400 ... 0xFFFF
I/O SPACE
SRAM DATA MEMORY
(reserved)
NVM LOCK BITS
(reserved)
CONFIGURATION BITS
(reserved)
CALIBRATION BITS
(reserved)
DEVICE ID BITS
(reserved)
FLASH PROGRAM MEMORY
(reserved)
7.3.1. Data Memory Access Times
The internal data SRAM access is performed in two clkCPU cycles as described in the following Figure.
Figure 7-2 On-chip Data SRAM Access Cycles
clk
WR
RD
Data
Data
Address Address valid
T1 T2 T3
Compute Address
Read Write
CPU
Memory Access Instruction Next Instruction
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7.4. I/O Memory
The I/O space definition of the device is shown in the Register Summary.
All ATtiny4/5/9/10 I/Os and peripherals are placed in the I/O space. All I/O locations may be accessed by
the LD and ST instructions, transferring data between the 16 general purpose working registers and the
I/O space. I/O Registers within the address range 0x00-0x1F are directly bit-accessible using the SBI and
CBI instructions, except USART registers. In these registers, the value of single bits can be checked by
using the SBIS and SBIC instructions. Refer to the Instruction Set Summary section for more details.
For compatibility with future devices, reserved bits should be written to zero if accessed. Reserved I/O
memory addresses should never be written.
Some of the Status Flags are cleared by writing a '1' to them; this is described in the flag descriptions.
Note that, unlike most other AVRs, the CBI and SBI instructions will only operate on the specified bit, and
can therefore be used on registers containing such Status Flags. The CBI and SBI instructions work with
registers 0x00-0x1F only.
The I/O and Peripherals Control Registers are explained in later sections.
Related Links
Register Summary on page 196
Instruction Set Summary on page 198
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8. Clock System
8.1. Clock Distribution
The following figure illustrates the principal clock systems in the device and their distribution. All the
clocks need not be active at a given time. In order to reduce power consumption, the clocks to modules
not being used can be halted by using different sleep modes, as described in the section on Power
Management and Sleep Modes. The clock systems are detailed below.
Figure 8-1 Clock Distribution
CLOCK CONTROL UNIT
GENERAL
I/O MODULES
ANALOG-TO-DIGITAL
CONVERTER
CPU
CORE
WATCHDOG
TIMER
RESET
LOGIC
CLOCK
PRESCALER
RAM
CLOCK
SWITCH
NVM
CALIBRATED
OSCILLATOR
clk
ADC
SOURCE CLOCK
clk
I/O
clk
CPU
clk
NVM
WATCHDOG
CLOCK
WATCHDOG
OSCILLATOR
EXTERNAL
CLOCK
Related Links
Power Management and Sleep Modes on page 40
8.2. Clock Subsystems
8.2.1. CPU Clock – clkCPU
The CPU clock is routed to parts of the system concerned with operation of the AVR core. Examples of
such modules are the General Purpose Register File, the System Registers and the SRAM data memory.
Halting the CPU clock inhibits the core from performing general operations and calculations.
8.2.2. I/O Clock – clkI/O
The I/O clock is used by the majority of the I/O modules, like Timer/Counter. The I/O clock is also used by
the External Interrupt module, but note that some external interrupts are detected by asynchronous logic,
allowing such interrupts to be detected even if the I/O clock is halted.
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8.2.3. NVM Clock – clkNVM
The NVM clock controls operation of the Non-Volatile Memory Controller. The NVM clock is usually active
simultaneously with the CPU clock.
8.2.4. ADC Clock – clkADC
The ADC is provided with a dedicated clock domain. This allows halting the CPU and I/O clocks in order
to reduce noise generated by digital circuitry. This gives more accurate ADC conversion results.
The ADC is available in ATtiny5/10, only.
8.3. Clock Sources
The device has the following clock source options, selectable by Clock Main Select Bits in Clock Main
Settings Register (CLKMSR.CLKMS). All synchronous clock signals are derived from the main clock. The
three alternative sources for the main clock are as follows:
•Calibrated Internal 8 MHz Oscillator
•External Clock
•Internal 128 kHz Oscillator.
Refer to description of Clock Main Select Bits in Clock Main Settings Register (CLKMSR.CLKMS) for how
to select and change the active clock source.
Related Links
CLKMSR on page 36
8.3.1. Calibrated Internal 8 MHz Oscillator
The calibrated internal oscillator provides an approximately 8 MHz clock signal. Though voltage and
temperature dependent, this clock can be very accurately calibrated by the user.
This clock may be selected as the main clock by setting the Clock Main Select bits in CLKMSR
(CLKMSR.CLKMS) to 0b00. Once enabled, the oscillator will operate with no external components.
During reset, hardware loads the calibration byte into the OSCCAL register and thereby automatically
calibrates the oscillator. The accuracy of this calibration is shown as Factory calibration in Accuracy of
Calibrated Internal Oscillator of Electrical Characteristics chapter.
When this oscillator is used as the main clock, the watchdog oscillator will still be used for the watchdog
timer and reset time-out. For more information on the pre-programmed calibration value, see section
Calibration Section.
Related Links
Calibration Section on page 155
Accuracy of Calibrated Internal Oscillator on page 164
Internal Oscillator Speed on page 188
CLKMSR on page 36
8.3.2. External Clock
To drive the device from an external clock source, CLKI should be driven as shown in the Figure below.
To run the device on an external clock, the CLKMSR.CLKMS must be programmed to '0b10':
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Table 8-1 External Clock Frequency
Frequency CLKMSR.CLKMS
0 - 16MHz 0b10
Figure 8-2 External Clock Drive Configuration
EXTERNAL
CLOCK
SIGNAL CLKI
GND
When applying an external clock, it is required to avoid sudden changes in the applied clock frequency to
ensure stable operation of the MCU. A variation in frequency of more than 2% from one clock cycle to the
next can lead to unpredictable behavior. It is required to ensure that the MCU is kept in Reset during the
changes.
Related Links
CLKMSR on page 36
8.3.3. Internal 128 kHz Oscillator
The internal 128 kHz oscillator is a low power oscillator providing a clock of 128 kHz. The frequency
depends on supply voltage, temperature and batch variations. This clock may be select as the main clock
by setting the CLKMSR.CLKMS to 0b01.
Related Links
CLKMSR on page 36
8.3.4. Switching Clock Source
The main clock source can be switched at run-time using the CLKMSR – Clock Main Settings Register.
When switching between any clock sources, the clock system ensures that no glitch occurs in the main
clock.
Related Links
CLKMSR on page 36
8.3.5. Default Clock Source
The calibrated internal 8 MHz oscillator is always selected as main clock when the device is powered up
or has been reset. The synchronous system clock is the main clock divided by 8, controlled by the
System Clock Prescaler. The Clock Prescaler Select Bits in Clock Prescale Register (CLKPSR.CLKPS)
can be written later to change the system clock frequency. See section “System Clock Prescaler”.
Related Links
CLKMSR on page 36
8.4. System Clock Prescaler
The system clock is derived from the main clock via the System Clock Prescaler. The system clock can
be divided by setting the “CLKPSR – Clock Prescale Register”. The system clock prescaler can be used
to decrease power consumption at times when requirements for processing power is low or to bring the
system clock within limits of maximum frequency. The prescaler can be used with all main clock source
options, and it will affect the clock frequency of the CPU and all synchronous peripherals.
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The System Clock Prescaler can be used to implement run-time changes of the internal clock frequency
while still ensuring stable operation.
8.4.1. Switching Prescaler Setting
When switching between prescaler settings, the system clock prescaler ensures that no glitch occurs in
the system clock and that no intermediate frequency is higher than neither the clock frequency
corresponding the previous setting, nor the clock frequency corresponding to the new setting.
The ripple counter that implements the prescaler runs at the frequency of the main clock, which may be
faster than the CPU's clock frequency. Hence, it is not possible to determine the state of the prescaler -
even if it were readable, and the exact time it takes to switch from one clock division to another cannot be
exactly predicted.
From the time the CLKPSR.CLKPS values are written, it takes between T1 + T2 and T1 + 2*T2 before the
new clock frequency is active. In this interval, two active clock edges are produced. Here, T1 is the
previous clock period, and T2 is the period corresponding to the new prescaler setting.
8.5. Starting
8.5.1. Starting from Reset
The internal reset is immediately asserted when a reset source goes active. The internal reset is kept
asserted until the reset source is released and the start-up sequence is completed. The start-up
sequence includes three steps, as follows.
1. The first step after the reset source has been released consists of the device counting the reset
start-up time. The purpose of this reset start-up time is to ensure that supply voltage has reached
sufficient levels. The reset start-up time is counted using the internal 128 kHz oscillator.
Note: The actual supply voltage is not monitored by the start-up logic. The device will count until
the reset start-up time has elapsed even if the device has reached sufficient supply voltage levels
earlier.
2. The second step is to count the oscillator start-up time, which ensures that the calibrated internal
oscillator has reached a stable state before it is used by the other parts of the system. The
calibrated internal oscillator needs to oscillate for a minimum number of cycles before it can be
considered stable.
3. The last step before releasing the internal reset is to load the calibration and the configuration
values from the Non-Volatile Memory to configure the device properly. The configuration time is
listed in the next table.
Table 8-2 Start-up Times when Using the Internal Calibrated Oscillator with Normal start-up time
Reset Oscillator Configuration Total start-up time
64 ms 6 cycles 21 cycles 64 ms + 6 oscillator cycles + 21 system clock cycles (1)
Note:
1. After powering up the device or after a reset the system clock is automatically set to calibrated
internal 8 MHz oscillator, divided by 8
8.5.2. Starting from Power-Down Mode
When waking up from Power-Down sleep mode, the supply voltage is assumed to be at a sufficient level
and only the oscillator start-up time is counted to ensure the stable operation of the oscillator. The
oscillator start-up time is counted on the selected main clock, and the start-up time depends on the clock
selected.
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Table 8-3 Start-up Time from Power-Down Sleep Mode.
Oscillator start-up time Total start-up time
6 cycles 6 oscillator cycles (1)
Note: 1. The start-up time is measured in main clock oscillator cycles.
8.5.3. Starting from Idle / ADC Noise Reduction / Standby Mode
When waking up from Idle, ADC Noise Reduction or Standby Mode, the oscillator is already running and
no oscillator start-up time is introduced.
The ADC is available in ATtiny5/10, only.
8.6. Register Description
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8.6.1. Clock Main Settings Register
Name: CLKMSR
Offset: 0x37
Reset: 0x00
Property:
-
Bit 7 6 5 4 3 2 1 0
CLKMS[1:0]
Access R/W R/W
Reset 0 0
Bits 1:0 – CLKMS[1:0]: Clock Main Select Bits
These bits select the main clock source of the system. The bits can be written at run-time to switch the
source of the main clock. The clock system ensures glitch free switching of the main clock source.
Table 8-4 Selection of Main Clock
CLKM Main Clock Source
00 Calibrated Internal 8 MHzOscillator
01 Internal 128 kHz Oscillator (WDT Oscillator)
10 External clock
11 Reserved
To avoid unintentional switching of main clock source, a protected change sequence must be followed to
change the CLKMS bits, as follows:
1. Write the signature for change enable of protected I/O register to register CCP.
2. Within four instruction cycles, write the CLKMS bits with the desired value.
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8.6.2. Oscillator Calibration Register
Name: OSCCAL
Offset: 0x39
Reset: xxxxxxxx
Property:
-
Bit 7 6 5 4 3 2 1 0
CAL[7:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset x x x x x x x x
Bits 7:0 – CAL[7:0]: Oscillator Calibration Value
The Oscillator Calibration Register is used to trim the Calibrated Internal RC Oscillator to remove process
variations from the oscillator frequency. A pre-programmed calibration value is automatically written to
this register during chip reset, giving the Factory calibrated frequency as specified in the table of
Calibration Accuracy of Internal RC Oscillator. The application software can write this register to change
the oscillator frequency. The oscillator can be calibrated to frequencies as specified in the table of
Calibration Accuracy of Internal RC Oscillator. Calibration outside that range is not guaranteed.
The CAL[7:0] bits are used to tune the frequency within the selected range. A setting of 0x00 gives the
lowest frequency in that range, and a setting of 0xFF gives the highest frequency in the range.
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8.6.3. Clock Prescaler Register
Name: CLKPSR
Offset: 0x36
Reset: 0x00000011
Property:
-
Bit 7 6 5 4 3 2 1 0
CLKPS[3:0]
Access R/W R/W R/W R/W
Reset 0 0 1 1
Bits 3:0 – CLKPS[3:0]: Clock Prescaler Select
These bits define the division factor between the selected clock source and the internal system clock.
These bits can be written run-time to vary the clock frequency to suit the application requirements. As the
divider divides the master clock input to the MCU, the speed of all synchronous peripherals is reduced
when a division factor is used. The division factors are given in the table below.
Table 8-5 Clock Prescaler Select
CLKPS[3:0] Clock Division Factor
0000 1
0001 2
0010 4
0011 8 (default)
0100 16
0101 32
0110 64
0111 128
1000 256
1001 Reserved
1010 Reserved
1011 Reserved
1100 Reserved
1101 Reserved
1110 Reserved
1111 Reserved
To avoid unintentional changes of clock frequency, a protected change sequence must be followed to
change the CLKPS bits:
1. Write the signature for change enable of protected I/O register to register CCP
2. Within four instruction cycles, write the desired value to CLKPS bits
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At start-up, CLKPS bits are reset to 0b0011 to select the clock division factor of 8. If the selected clock
source has a frequency higher than the maximum allowed the application software must make sure a
sufficient division factor is used. To make sure the write procedure is not interrupted, interrupts must be
disabled when changing prescaler settings.
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9. Power Management and Sleep Modes
9.1. Overview
The high performance and industry leading code efficiency makes the AVR microcontrollers an ideal
choise for low power applications. In addition, sleep modes enable the application to shut down unused
modules in the MCU, thereby saving power. The AVR provides various sleep modes allowing the user to
tailor the power consumption to the application’s requirements.
9.2. Sleep Modes
The following Table shows the different sleep modes and their wake up
Table 9-1 Active Clock Domains and Wake-up Sources in the Different Sleep Modes.
Active Clock Domains Oscillators Wake-up Sources
Sleep Mode clkCPU clkNVM clkIO clkADC(2) Main Clock
Source
Enabled
INT0 and Pin
Change
ADC(2) Other I/O Watchdog
Interrupt
VLM Interrupt
Idle Yes Yes Yes Yes Yes Yes Yes Yes
ADC Noise
Reduction
Yes Yes Yes(1) Yes Yes Yes
Standby Yes Yes(1) Yes
Power-down Yes(1) Yes
Note:
1. For INT0, only level interrupt.
2. The ADC is available in ATtiny5/10, only.
To enter any of the four sleep modes (Idle, ADC Noise Reduction, Power-down or Standby), the Sleep
Enable bit in the Sleep Mode Control Register (SMCR.SE) must be written to '1' and a SLEEP instruction
must be executed. Sleep Mode Select bits (SMCR.SM) select which sleep mode will be activated by the
SLEEP instruction.
If an enabled interrupt occurs while the MCU is in a sleep mode, the MCU wakes up. The MCU is then
halted for four cycles in addition to the start-up time, executes the interrupt routine, and resumes
execution from the instruction following SLEEP. The contents of the Register File and SRAM are
unaltered when the device wakes up from sleep. If a reset occurs during sleep mode, the MCU wakes up
and executes from the Reset Vector.
Note: If a level triggered interrupt is used for wake-up the changed level must be held for some time to
wake up the MCU (and for the MCU to enter the interrupt service routine). See External Interrupts for
details.
Related Links
Interrupts on page 56
SMCR on page 44
9.2.1. Idle Mode
When the SMCR.SM is written to '0x000', the SLEEP instruction makes the MCU enter Idle mode,
stopping the CPU but allowing the Analog Comparator, Timer/Counters, Watchdog, and the interrupt
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system to continue operating. This sleep mode basically halts clkCPU and clkNVM, while allowing the other
clocks to run.
Idle mode enables the MCU to wake up from external triggered interrupts as well as internal ones like the
timer overflow. If wake-up from the Analog Comparator interrupt is not required, the Analog Comparator
can be powered down by setting the ACD bit in the Analog Comparator Control and Status Register
(ACSR.ACD). This will reduce power consumption in Idle mode. If the ADC is enabled (ATtiny5/10, only),
a conversion starts automatically when this mode is entered.
Related Links
ACSR on page 121
SMCR on page 44
9.2.2. ADC Noise Reduction Mode
When the SMCR.SM is written to '0x001', the SLEEP instruction makes the MCU enter ADC Noise
Reduction mode, stopping the CPU but allowing the ADC, the external interrupts and the Watchdog to
continue operating (if enabled). This sleep mode basically halts clkI/O, clkCPU, and clkNVM, while allowing
the other clocks to run.
This improves the noise environment for the ADC, enabling higher resolution measurements. If the ADC
is enabled, a conversion starts automatically when this mode is entered.
This mode is available in all devices, although only ATtiny5/10 are equipped with an ADC.
Related Links
SMCR on page 44
9.2.3. Power-Down Mode
When the SMCR.SM is written to '0x010', the SLEEP instruction makes the MCU enter Power-Down
mode. In this mode, the external Oscillator is stopped, while the external interrupts and the Watchdog
continue operating (if enabled).
Only an these events can wake up the MCU:
•Watchdog System Reset
•External level interrupt on INT0
•Pin change interrupt
This sleep mode basically halts all generated clocks, allowing operation of asynchronous modules only.
Related Links
SMCR on page 44
9.2.4. Standby Mode
When the SMCR.SM is written to '0x100', the SLEEP instruction makes the MCU enter Standby mode.
This mode is identical to Power-Down with the exception that the Oscillator is kept running. This reduces
wake-up time, because the oscillator is already running and doesn't need to be started up.
Related Links
SMCR on page 44
9.3. Power Reduction Register
The Power Reduction Register (PRR) provides a method to stop the clock to individual peripherals to
reduce power consumption. When the clock for a peripheral is stopped then:
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•The current state of the peripheral is frozen.
•The associated registers can not be read or written.
•Resources used by the peripheral will remain occupied.
The peripheral should in most cases be disabled before stopping the clock. Clearing the PRR bit wakes
up the peripheral and puts it in the same state as before shutdown.
Peripheral module shutdown can be used in Idle mode and Active mode to significantly reduce the overall
power consumption. In all other sleep modes, the clock is already stopped.
Related Links
PRR on page 45
9.4. Minimizing Power Consumption
There are several possibilities to consider when trying to minimize the power consumption in an AVR
controlled system. In general, sleep modes should be used as much as possible, and the sleep mode
should be selected so that as few as possible of the device’s functions are operating. All functions not
needed should be disabled. In particular, the following modules may need special consideration when
trying to achieve the lowest possible power consumption.
9.4.1. Analog Comparator
When entering Idle mode, the Analog Comparator should be disabled if not used. In the power-down
mode, the analog comparator is automatically disabled. See Analog Comparator for further details.
Related Links
Analog Comparator on page 120
9.4.2. Analog to Digital Converter
If enabled, the ADC will be enabled in all sleep modes. To save power, the ADC should be disabled
before entering any sleep mode. When the ADC is turned off and on again, the next conversion will be an
extended conversion.
Related Links
ADC - Analog to Digital Converter on page 124
9.4.3. Watchdog Timer
If the Watchdog Timer is not needed in the application, the module should be turned off. If the Watchdog
Timer is enabled, it will be enabled in all sleep modes and hence always consume power. In the deeper
sleep modes, this will contribute significantly to the total current consumption.
Related Links
Watchdog Timer on page 49
9.4.4. Port Pins
When entering a sleep mode, all port pins should be configured to use minimum power. The most
important is then to ensure that no pins drive resistive loads. In sleep modes where both the I/O clock
(clkI/O) is stopped, the input buffers of the device will be disabled. This ensures that no power is
consumed by the input logic when not needed. In some cases, the input logic is needed for detecting
wake-up conditions, and it will then be enabled. Refer to the section Digital Input Enable and Sleep
Modes for details on which pins are enabled. If the input buffer is enabled and the input signal is left
floating or have an analog signal level close to VCC/2, the input buffer will use excessive power.
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For analog input pins, the digital input buffer should be disabled at all times. An analog signal level close
to VCC/2 on an input pin can cause significant current even in active mode. Digital input buffers can be
disabled by writing to the Digital Input Disable Registers (DIDR).
Related Links
Digital Input Enable and Sleep Modes on page 69
DIDR0 on page 123
9.5. Register Description
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9.5.1. Sleep Mode Control Register
The Sleep Mode Control Register contains control bits for power management.
Name: SMCR
Offset: 0x3A
Reset: 0x00
Property:
Bit 7 6 5 4 3 2 1 0
SM[2:0] SE
Access R/W R/W R/W R/W
Reset 0 0 0 0
Bits 3:1 – SM[2:0]: Sleep Mode Select
The SM[2:0] bits select between the five available sleep modes.
Table 9-2 Sleep Mode Select
SM[2:0] Sleep Mode
000 Idle
001 ADC Noise Reduction
010 Power-down
011 Reserved
100 Standby
101 Reserved
110 Reserved
111 Reserved
Note:
1. This mode is available in all devices, although only ATtiny5/10 are equipped with an ADC
Bit 0 – SE: Sleep Enable
The SE bit must be written to logic one to make the MCU enter the sleep mode when the SLEEP
instruction is executed. To avoid the MCU entering the sleep mode unless it is the programmer’s purpose,
it is recommended to write the Sleep Enable (SE) bit to one just before the execution of the SLEEP
instruction and to clear it immediately after waking up.
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9.5.2. Power Reduction Register
Name: PRR
Offset: 0x35
Reset: 0x00
Property:
-
Bit 7 6 5 4 3 2 1 0
PRADC PRTIM0
Access R/W R/W
Reset 0 0
Bit 1 – PRADC: Power Reduction ADC
Writing a logic one to this bit shuts down the ADC. The ADC must be disabled before shut down. The
analog comparator cannot use the ADC input MUX when the ADC is shut down.
The ADC is available in ATtiny5/10, only.
Bit 0 – PRTIM0: Power Reduction Timer/Counter0
Writing a logic one to this bit shuts down the Timer/Counter0 module. When the Timer/Counter0 is
enabled, operation will continue like before the shutdown.
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10. System Control and Reset
10.1. Resetting the AVR
During reset, all I/O Registers are set to their initial values, and the program starts execution from the
Reset Vector. The instruction placed at the Reset Vector must be an Relative Jump instruction (RJMP) to
the reset handling routine. If the program never enables an interrupt source, the Interrupt Vectors are not
used, and regular program code can be placed at these locations. The circuit diagram in the next shows
the reset logic. Electrical parameters of the reset circuitry are defined in section System and Reset
Characteristics.
Figure 10-1 Reset Logic
Re s e t Flag Registe r
(RS TFLR)
Delay Counters
CK
TIMEOUT
WDRF
EXTRF
PORF
DATA BUS
Clock
Ge ne ra tor
SPIKE
FILTER
Pull-up Re s is tor
Wa tchdog
Os cilla tor
Power-on Rese t
Circuit
VLM
The I/O ports of the AVR are immediately reset to their initial state when a reset source goes active. This
does not require any clock source to be running.
After all reset sources have gone inactive, a delay counter is invoked, stretching the internal reset. This
allows the power to reach a stable level before normal operation starts.
Related Links
System and Reset Characteristics on page 165
Starting from Reset on page 34
10.2. Reset Sources
The device has four sources of reset:
•Power-on Reset. The MCU is reset when the supply voltage is less than the Power-on Reset
threshold (VPOT).
•External Reset. The MCU is reset when a low level is present on the RESET pin for longer than the
minimum pulse length.
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•Watchdog System Reset. The MCU is reset when the Watchdog Timer period expires and the
Watchdog System Reset mode is enabled.
10.2.1. Power-on Reset
A Power-on Reset (POR) pulse is generated by an On-chip detection circuit. The POR is activated
whenever VCC is below the detection level. The POR circuit can be used to trigger the start-up Reset, as
well as to detect a failure in supply voltage.
A Power-on Reset (POR) circuit ensures that the device is reset from Power-on. Reaching the Power-on
Reset threshold voltage invokes the delay counter, which determines how long the device is kept in Reset
after VCC rise. The Reset signal is activated again, without any delay, when VCC decreases below the
detection level.
Figure 10-2 MCU Start-up, RESET Tied to VCC
V
RESET
TIME-OUT
INTERNAL
RESET
tTOUT
VPOT
VRST
CC
Figure 10-3 MCU Start-up, RESET Extended Externally
RESET
TIME-OUT
INTERNAL
RESET
tTOUT
VPOT
VRST
VCC
Related Links
System and Reset Characteristics on page 165
10.2.2. VCC Level Monitoring
ATtiny4/5/9/10 have a VCC Level Monitoring (VLM) circuit that compares the voltage level at the VCC pin
against fixed trigger levels. The trigger levels are set with VLM[2:0] bits, see VLMCSR – VCC Level
Monitoring Control and Status register.
The VLM circuit provides a status flag, VLMF, that indicates if voltage on the VCC pin is below the
selected trigger level. The flag can be read from VLMCSR, but it is also possible to have an interrupt
generated when the VLMF status flag is set. This interrupt is enabled by the VLMIE bit in the VLMCSR
register. The flag can be cleared by changing the trigger level or by writing it to zero. The flag is
automatically cleared when the voltage at VCC rises back above the selected trigger level.
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The VLM can also be used to improve reset characteristics at falling supply. Without VLM, the Power-On
Reset (POR) does not activate before supply voltage has dropped to a level where the MCU is not
necessarily functional any more. With VLM, it is possible to generate a reset earlier.
When active, the VLM circuit consumes some power, as illustrated in the figure of VCC Level Monitor
Current vs. VCC in Typical Characteristics. To save power the VLM circuit can be turned off completely, or
it can be switched on and off at regular intervals. However, detection takes some time and it is therefore
recommended to leave the circuitry on long enough for signals to settle. See VCC Level Monitor.
When VLM is active and voltage at VCC is above the selected trigger level operation will be as normal and
the VLM can be shut down for a short period of time. If voltage at VCC drops below the selected threshold
the VLM will either flag an interrupt or generate a reset, depending on the configuration.
When the VLM has been configured to generate a reset at low supply voltage it will keep the device in
reset as long as VCC is below the reset level. If supply voltage rises above the reset level the condition is
removed and the MCU will come out of reset, and initiate the power-up start-up sequence.
If supply voltage drops enough to trigger the POR then PORF is set after supply voltage has been
restored.
Related Links
VLMCSR on page 54
VCC Level Monitor on page 166
Electrical Characteristics on page 162
Typical Characteristics on page 169
10.2.3. External Reset
An External Reset is generated by a low level on the RESET pin. Reset pulses longer than the minimum
pulse width will generate a reset, even if the clock is not running. Shorter pulses are not guaranteed to
generate a reset. When the applied signal reaches the Reset Threshold Voltage (VRST) on its positive
edge, the delay counter starts the MCU after the Time-out period (tTOUT ) has expired. The External Reset
can be disabled by the RSTDISBL fuse.
Figure 10-4 External Reset During Operation
CC
Related Links
System and Reset Characteristics on page 165
10.2.4. Watchdog System Reset
When the Watchdog times out, it will generate a short reset pulse of one CK cycle duration. On the falling
edge of this pulse, the delay timer starts counting the Time-out period tTOUT.
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Figure 10-5 Watchdog System Reset During Operation
CK
CC
10.3. Watchdog Timer
If the watchdog timer is not needed in the application, the module should be turned off. If the watchdog
timer is enabled, it will be enabled in all sleep modes and hence always consume power. In the deeper
sleep modes, this will contribute significantly to the total current consumption.
Refer to Watchdog System Reset on page 48 for details on how to configure the watchdog timer.
10.3.1. Overview
The Watchdog Timer is clocked from an on-chip oscillator, which runs at 128 kHz, as the next figure. By
controlling the Watchdog Timer prescaler, the Watchdog Reset interval can be adjusted. The Watchdog
Reset (WDR) instruction resets the Watchdog Timer. The Watchdog Timer is also reset when it is
disabled and when a device reset occurs. Ten different clock cycle periods can be selected to determine
the reset period. If the reset period expires without another Watchdog Reset, the device resets and
executes from the Reset Vector.
Figure 10-6 Watchdog Timer
OS C/2K
OS C/4K
OS C/8K
OS C/16K
OS C/32K
OS C/64K
OS C/128K
OS C/256K
OS C/512K
OSC/1024K
MCU RESET
WATCHDOG
PRESCALER
128 kHz
OS CILLATOR
WATCHDOG
RES ET
WDP0
WDP1
WDP2
WDP3
WDE
MUX
The Wathdog Timer can also be configured to generate an interrupt instead of a reset. This can be very
helpful when using the Watchdog to wake-up from Power-down.
To prevent unintentional disabling of the Watchdog or unintentional change of time-out period, two
different safety levels are selected by the fuse WDTON. See Procedure for Changing the Watchdog Timer
Configuration on page 50 for details.
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Table 10-1 WDT Configuration as a Function of the Fuse Settings of WDTON
WDTON Safety Level WDT Initial
State
How to Disable the
WDT
How to Change Time-
out
Unprogrammed 1 Disabled Protected change
sequence
No limitations
Programmed 2 Enabled Always enabled Protected change
sequence
10.3.2. Procedure for Changing the Watchdog Timer Configuration
The sequence for changing configuration differs between the two safety levels, as follows:
10.3.2.1. Safety Level 1
In this mode, the Watchdog Timer is initially disabled, but can be enabled by writing the WDE bit to one
without any restriction. A special sequence is needed when disabling an enabled Watchdog Timer. To
disable an enabled Watchdog Timer, the following procedure must be followed:
1. Write the signature for change enable of protected I/O registers to register CCP
2. Within four instruction cycles, in the same operation, write WDE and WDP bits
10.3.2.2. Safety Level 2
In this mode, the Watchdog Timer is always enabled, and the WDE bit will always read as one. A
protected change is needed when changing the Watchdog Time-out period. To change the Watchdog
Time-out, the following procedure must be followed:
1. Write the signature for change enable of protected I/O registers to register CCP
2. Within four instruction cycles, write the WDP bit. The value written to WDE is irrelevant
10.3.3. Code Examples
The following code example shows how to turn off the WDT. The example assumes that interrupts are
controlled (e.g., by disabling interrupts globally) so that no interrupts will occur during execution of these
functions.
Assembly Code Example
WDT_off:
wdr
; Clear WDRF in RSTFLR
in r16, RSTFLR
andi r16, ~(1<<WDRF)
out RSTFLR, r16
; Write signature for change enable of protected I/O register
ldi r16, 0xD8
out CCP, r16
; Within four instruction cycles, turn off WDT
ldi r16, (0<<WDE)
out WDTCSR, r16
ret
Note: See About Code Examples.
Related Links
About Code Examples on page 14
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10.4. Register Description
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10.4.1. Watchdog Timer Control Register
Name: WDTCSR
Offset: 0x31
Reset: 0x00
Property:
-
Bit 7 6 5 4 3 2 1 0
WDIF WDIE WDP3 WDE WDP2 WDP1 WDP0
Access R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 x 0 0 0
Bit 7 – WDIF: Watchdog Interrupt Flag
This bit is set when a time-out occurs in the Watchdog Timer and the Watchdog Timer is configured for
interrupt. WDIF is cleared by hardware when executing the corresponding interrupt handling vector.
Alternatively, WDIF is cleared by writing a logic one to the flag. When the I-bit in SREG and WDIE are set,
the Watchdog Time-out Interrupt is executed.
Bit 6 – WDIE: Watchdog Interrupt Enable
When this bit is written to one and the I-bit in the Status Register is set, the Watchdog Interrupt is
enabled. If WDE is cleared in combination with this setting, the Watchdog Timer is in Interrupt Mode, and
the corresponding interrupt is executed if time-out in the Watchdog Timer occurs. If WDE is set, the
Watchdog Timer is in Interrupt and System Reset Mode. The first time-out in the Watchdog Timer will set
WDIF. Executing the corresponding interrupt vector will clear WDIE and WDIF automatically by hardware
(the Watchdog goes to System Reset Mode).
This is useful for keeping the Watchdog Timer security while using the interrupt. To stay in Interrupt and
System Reset Mode, WDIE must be set after each interrupt. This should however not be done within the
interrupt service routine itself, as this might compromise the safety-function of the Watchdog System
Reset mode. If the interrupt is not executed before the next time-out, a System Reset will be applied.
Table 10-2 Watchdog Timer Configuration
WDTON(1) WDE WDIE Mode Action on Time-out
1 0 0 Stopped None
1 0 1 Interrupt Mode Interrupt
1 1 0 System Reset Mode Reset
1 1 1 Interrupt and System Reset Mode Interrupt, then go to System Reset Mode
0 X X System Reset Mode Reset
Note:
1. WDTON Fuse set to “0” means programmed and “1” means unprogrammed.
Bit 3 – WDE: Watchdog System Reset Enable
WDE is overridden by WDRF in RSTFLR. This means that WDE is always set when WDRF is set. To
clear WDE, WDRF must be cleared first. This feature ensures multiple resets during conditions causing
failure, and a safe start-up after the failure.
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Bits 5,2:0 – WDPn: Watchdog Timer Prescaler [n=3:0]
The WDP[3:0] bits determine the Watchdog Timer prescaling when the Watchdog Timer is running. The
different prescaling values and their corresponding time-out periods are shown in the table below.
Table 10-3 Watchdog Timer Prescale Select
WDP[3:0] Number of WDT Oscillator Cycles Typical Time-out at VCC = 5.0V
0000 2K (2048) cycles 16ms
0001 4K (4096) cycles 32ms
0010 8K (8192) cycles 64ms
0011 16K (16384) cycles 0.125s
0100 32K (32768) cycles 0.25s
0101 64K (65536) cycles 0.5s
0110 128K (131072) cycles 1.0s
0111 256K (262144) cycles 2.0s
1000 512K (524288) cycles 4.0s
1001 1024K (1048576) cycles 8.0s
1010 Reserved Reserved
1011 Reserved Reserved
1100 Reserved Reserved
1101 Reserved Reserved
1110 Reserved Reserved
1111 Reserved Reserved
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10.4.2. VCC Level Monitoring Control and Status register
Name: VLMCSR
Offset: 0x34
Reset: 0x00
Property:
-
Bit 7 6 5 4 3 2 1 0
VLMF VLMIE VLM[2:0]
Access R R/W R/W R/W R/W
Reset 0 0 0 0 0
Bit 7 – VLMF: VLM Flag
This bit is set by the VLM circuit to indicate that a voltage level condition has been triggered. The bit is
cleared when the trigger level selection is set to “Disabled”, or when voltage at VCC rises above the
selected trigger level.
Bit 6 – VLMIE: VLM Interrupt Enable
When this bit is set the VLM interrupt is enabled. A VLM interrupt is generated every time the VLMF flag
is set.
Bits 2:0 – VLM[2:0]: Trigger Level of Voltage Level Monitor
These bits set the trigger level for the voltage level monitor.
Table 10-4 Setting the Trigger Level of Voltage Level Monitor
VLM[2:0] Label Description
000 VLM0 Voltage Level Monitor disabled
001 VLM1L Triggering generates a regular Power-On Reset (POR).
The VLM flag is not set
010 VLM1H
011 VLM2 Triggering sets the VLM Flag (VLMF) and generates a VLM interrupt, if enabled
100 VLM3
101 Not allowed
110 Not allowed
111 Not allowed
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10.4.3. Reset Flag Register
Name: RSTFLR
Offset: 0x3B
Reset: N/A
Property:
-
Bit 7 6 5 4 3 2 1 0
WDRF EXTRF PORF
Access R/W R/W R/W
Reset x x x
Bit 3 – WDRF: Watchdog Reset Flag
This bit is set if a Watchdog Reset occurs. The bit is reset by a Power-on Reset, or by writing a logic zero
to the flag.
Bit 1 – EXTRF: External Reset Flag
This bit is set if an External Reset occurs. The bit is reset by a Power-on Reset, or by writing a logic zero
to the flag.
Bit 0 – PORF: Power-on Reset Flag
This bit is set if a Power-on Reset occurs. The bit is reset only by writing a logic zero to the flag. To make
use of the Reset Flags to identify a reset condition, the user should read and then reset the MCUSR as
early as possible in the program. If the register is cleared before another reset occurs, the source of the
reset can be found by examining the Reset Flags.
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11. Interrupts
11.1. Overview
This section describes the specifics of the interrupt handling of the device. For a general explanation of
the AVR interrupt handling, refer to the description of Reset and Interrupt Handling.
Related Links
Reset and Interrupt Handling on page 19
11.2. Interrupt Vectors
Interrupt vectors are described in the table below.
Table 11-1 Reset and Interrupt Vectors
Vector No. Program Address Source Interrupt Definition
1 0x000 RESET External Pin, Power-on Reset, VLM Reset and
Watchdog Reset
2 0x001 INT0 External Interrupt Request 0
3 0x002 PCINT0 Pin Change Interrupt Request 0
4 0x003 TIM0_CAPT Timer/Counter0 Capture
5 0x004 TIM0_OVF Timer/Counter0 Overflow
6 0x005 TIM0_COMPA Timer/Counter0 Compare Match A
7 0x006 TIM0_COMPB Timer/Counter0 Compare Match B
8 0x007 ANA_COMP Analog Comparator
9 0x008 WDT Watchdog Time-out Interrupt
10 0x009 VLM VCC Voltage Level Monitor
11 0x00A ADC ADC Conversion Complete(1)
Note:
1. The ADC is only available in ATtiny5/10.
In case the program never enables an interrupt source, the Interrupt Vectors will not be used and,
consequently, regular program code can be placed at these locations.
The most typical and general program setup for the Reset and Interrupt Vector Addresses in this device
is:
Address Labels Code Comments
0x000 rjmp RESET ; Reset Handler
0x001 rjmp INT0 ; IRQ0 Handler
0x002 rjmp PCINT0 ; PCINT0 Handler
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0x003 rjmp TIM0_CAPT ; Timer0 Capture Handler
0x004 rjmp TIM0_OVF ; Timer0 Overflow Handler
0x005 rjmp TIM0_COMPA ; Timer0 Compare A Handler
0x006 rjmp TIM0_COMPB ; Timer0 Compare B Handler
0x007 rjmp ANA_COMP ; Analog Comparator Handler
0x008 rjmp WDT ; Watchdog Interrupt Handler
0x009 rjmp VLM ; Voltage Level Monitor Handler
0x00A rjmp ADC ; ADC Conversion Handler
<continues> ... ... ...
<continued>
0x000B RESET: ldi r16, high (RAMEND) ; Main program start
0x000C out SPH,r16 ; Set Stack Pointer
0x000D ldi r16, low (RAMEND) ; to top of RAM
0x000E out SPL,r16
0x000F sei ; Enable interrupts
0x0010 <instr>
... ...
11.3. External Interrupts
The External Interrupts are triggered by the INT0 pins or any of the PCINT[3:0] pins. Observe that, if
enabled, the interrupts will trigger even if the INT0 or PCINT[3:0] pins are configured as outputs. This
feature provides a way of generating a software interrupt. The pin change interrupt PCI0 will trigger if any
enabled PCINT[3:0] pin toggles. The Pin Change Mask 0/1 Register (PCMSK 0/1) controls which pins
contribute to the pin change interrupts. Pin change interrupts on PCINT[3:0] are detected asynchronously.
This implies that these interrupts can be used for waking the part also from sleep modes other than Idle
mode.
The INT0 interrupts can be triggered by a falling or rising edge or a low level. This is set up as indicated in
the specification for the External Interrupt Control Register A (EICRA). When the INT0 interrupts are
enabled and are configured as level triggered, the interrupts will trigger as long as the pin is held low.
Note that recognition of falling or rising edge interrupts on INT0 requires the presence of an I/O clock,
described in Clock Systems and their Distribution chapter.
Related Links
EICRA on page 59
Clock System on page 31
PCMSK on page 64
11.3.1. Low Level Interrupt
A low level interrupt on INT0 is detected asynchronously. This means that the interrupt source can be
used for waking the part also from sleep modes other than Idle (the I/O clock is halted in all sleep modes
except Idle).
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Note that if a level triggered interrupt is used for wake-up from Power-down, the required level must be
held long enough for the MCU to complete the wake-up to trigger the level interrupt. If the level
disappears before the end of the Start-up Time, the MCU will still wake up, but no interrupt will be
generated. The start-up time is defined as described in Clock System
If the low level on the interrupt pin is removed before the device has woken up then program execution
will not be diverted to the interrupt service routine but continue from the instruction following the SLEEP
command.
Related Links
Clock System on page 31
11.3.2. Pin Change Interrupt Timing
An example of timing of a pin change interrupt is shown in the following figure.
Figure 11-1 Timing of pin change interrupts
clk
PCINT(0)
pin_lat
pin_sync
pcint_in_(0)
pcint_syn
pcint_setflag
PCIF
PCINT(0)
pin_sync
pcint_syn
pin_lat
D Q
LE
pcint_setflag
PCIF
clk
clk
PCINT(0) in PCMSK(x)
pcint_in_(0) 0
x
11.4. Register Description
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11.4.1. External Interrupt Control Register A
The External Interrupt Control Register A contains control bits for interrupt sense control.
Name: EICRA
Offset: 0x15
Reset: 0x00
Property:
-
Bit 7 6 5 4 3 2 1 0
ISC0[1:0]
Access R/W R/W
Reset 0 0
Bits 1:0 – ISC0[1:0]: Interrupt Sense Control 0
The External Interrupt 0 is activated by the external pin INT0 if the SREG I-flag and the corresponding
interrupt mask are set. The level and edges on the external INT0 pin that activate the interrupt are defined
in table below. The value on the INT0 pin is sampled before detecting edges. If edge or toggle interrupt is
selected, pulses that last longer than one clock period will generate an interrupt. Shorter pulses are not
guaranteed to generate an interrupt. If low level interrupt is selected, the low level must be held until the
completion of the currently executing instruction to generate an interrupt.
Value Description
00 The low level of INT0 generates an interrupt request.
01 Any logical change on INT0 generates an interrupt request.
10 The falling edge of INT0 generates an interrupt request.
11 The rising edge of INT0 generates an interrupt request.
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11.4.2. External Interrupt Mask Register
Name: EIMSK
Offset: 0x13
Reset: 0x00
Property:
-
Bit 7 6 5 4 3 2 1 0
INT0
Access R/W
Reset 0
Bit 0 – INT0: External Interrupt Request 0 Enable
When the INT0 bit is set ('1') and the I-bit in the Status Register (SREG) is set ('1'), the external pin
interrupt is enabled. The Interrupt Sense Control 0 bits in the External Interrupt Control Register A
(EICRA.ISC0) define whether the external interrupt is activated on rising and/or falling edge of the INT0
pin or level sensed. Activity on the pin will cause an interrupt request even if INT0 is configured as an
output. The corresponding interrupt of External Interrupt Request 0 is executed from the INT0 Interrupt
Vector.
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11.4.3. External Interrupt Flag Register
Name: EIFR
Offset: 0x14
Reset: 0x00
Property:
-
Bit 7 6 5 4 3 2 1 0
INTF0
Access R/W
Reset 0
Bit 0 – INTF0: External Interrupt Flag 0
When an edge or logic change on the INT0 pin triggers an interrupt request, INTF0 becomes set (one). If
the I-bit in SREG and the INT0 bit in EIMSK are set (one), the MCU will jump to the corresponding
Interrupt Vector. The flag is cleared when the interrupt routine is executed. Alternatively, the flag can be
cleared by writing a logical one to it. This flag is always cleared when INT0 is configured as a level
interrupt.
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11.4.4. Pin Change Interrupt Control Register
Name: PCICR
Offset: 0x12
Reset: 0x00
Property:
-
Bit 7 6 5 4 3 2 1 0
PCIE0
Access R/W
Reset 0
Bit 0 – PCIE0: Pin Change Interrupt Enable 0
When the PCIE0 bit is set (one) and the I-bit in the Status Register (SREG) is set (one), pin change
interrupt 0 is enabled. Any change on any enabled PCINT[3:0] pin will cause an interrupt. The
corresponding interrupt of Pin Change Interrupt Request is executed from the PCI0 Interrupt Vector.
PCINT[3:0] pins are enabled individually by the PCMSK Register.
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11.4.5. Pin Change Interrupt Flag Register
Name: PCIFR
Offset: 0x11
Reset: 0x00
Property:
-
Bit 7 6 5 4 3 2 1 0
PCIF0
Access R/W
Reset 0
Bit 0 – PCIF0: Pin Change Interrupt Flag 0
When a logic change on any PCINT[3:0] pin triggers an interrupt request, PCIF0 becomes set (one). If the
I-bit in SREG and the PCIE0 bit in PCICR are set (one), the MCU will jump to the corresponding Interrupt
Vector. The flag is cleared when the interrupt routine is executed. Alternatively, the flag can be cleared by
writing a logical one to it.
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11.4.6. Pin Change Mask Register
Name: PCMSK
Offset: 0x10
Reset: 0x00
Property:
-
Bit 7 6 5 4 3 2 1 0
PCINT3 PCINT2 PCINT1 PCINT0
Access R/W R/W R/W R/W
Reset 0 0 0 0
Bits 3:0 – PCINTn: Pin Change Enable Mask [n = 3:0]
Each PCINT[3:0] bit selects whether pin change interrupt is enabled on the corresponding I/O pin. If
PCINT[3:0] is set and the PCIE0 bit in PCICR is set, pin change interrupt is enabled on the corresponding
I/O pin. If PCINT[3:0] is cleared, pin change interrupt on the corresponding I/O pin is disabled.
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12. I/O-Ports
12.1. Overview
All AVR ports have true Read-Modify-Write functionality when used as general digital I/O ports. This
means that the direction of one port pin can be changed without unintentionally changing the direction of
any other pin with the SBI and CBI instructions. The same applies when changing drive value (if
configured as output) or enabling/disabling of pull-up resistors (if configured as input). Each output buffer
has symmetrical drive characteristics with both high sink and source capability. The pin driver is strong
enough to drive LED displays directly. All port pins have individually selectable pull-up resistors with a
supply-voltage invariant resistance. All I/O pins have protection diodes to both VCC and Ground as
indicated in the following figure.
Figure 12-1 I/O Pin Equivalent Schematic
Cpin
Logic
Rpu
See Figure
"General Digital I/O" for
Details
Pxn
All registers and bit references in this section are written in general form. A lower case “x” represents the
numbering letter for the port, and a lower case “n” represents the bit number. However, when using the
register or bit defines in a program, the precise form must be used. For example, PORTB3 for bit no. 3 in
Port B, here documented generally as PORTxn.
Four I/O memory address locations are allocated for each port, one each for the Data Register – PORTx,
Data Direction Register – DDRx, Pull-up Enable Register – PUEx, and the Port Input Pins – PINx. The
Port Input Pins I/O location is read only, while the Data Register and the Data Direction Register are read/
write. However, writing '1' to a bit in the PINx Register will result in a toggle in the corresponding bit in the
Data Register. In addition, the Pull-up Disable – PUD bit in MCUCR disables the pull-up function for all
pins in all ports when set.
Using the I/O port as General Digital I/O is described in next section. Most port pins are multiplexed with
alternate functions for the peripheral features on the device. How each alternate function interferes with
the port pin is described in Alternate Port Functions section in this chapter. Refer to the individual module
sections for a full description of the alternate functions.
Enabling the alternate function of some of the port pins does not affect the use of the other pins in the
port as general digital I/O.
Related Links
Electrical Characteristics on page 162
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12.2. Ports as General Digital I/O
The ports are bi-directional I/O ports with optional internal pull-ups. The following figure shows a
functional description of one I/O-port pin, here generically called Pxn.
Figure 12-2 General Digital I/O
clk
RPx
RRx
RDx
WDx
WEx
SYNCHRONIZER
WDx: WRITE DDRx
WRx: WRITE PORTx
RRx: READ PORTx REGISTER
RPx: READ PORTx PIN
clk
I/O
: I/O CLOCK
RDx: READ DDRx
WEx: WRITE PUEx
REx: READ PUEx
D
L
Q
Q
REx
RESET
RESET
Q
QD
Q
Q D
CLR
PORTxn
Q
Q D
CLR
DDxn
PINxn
DATA BUS
SLEEP
SLEEP: SLEEP CONTROL
Pxn
I/O
WPx
RESET
Q
Q D
CLR
PUExn
0
1
WRx
WPx: WRITE PINx REGISTER
Note: WEx, WRx, WPx, WDx, REx, RRx, RPx, and RDx are common to all pins within the same port.
clkI/O, SLEEP are common to all ports.
12.2.1. Configuring the Pin
Each port pin consists of four register bits: DDxn, PORTxn, PUExn, and PINxn. As shown in the Register
Description in this chapter, the DDxn bits are accessed at the DDRx I/O address, the PORTxn bits at the
PORTx I/O address, and the PINxn bits at the PINx I/O address.
The DDxn bit in the DDRx Register selects the direction of this pin. If DDxn is written to '1', Pxn is
configured as an output pin. If DDxn is written to '0', Pxn is configured as an input pin.
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If PORTxn is written to '1' when the pin is configured as an input pin, the pull-up resistor is activated. To
switch the pull-up resistor off, PORTxn has to be written to '0' or the pin has to be configured as an output
pin. The port pins are tri-stated when reset condition becomes active, even if no clocks are running.
Table 12-1 Port Pin Configurations
DDxn PORTxn PUExn I/O Pull-up Comment
0 x 0 Input No Tri-state (hi-Z)
0 x 1 Input Yes Sources current if pulled low externally
1 0 0 Output No Output low (sink)
1 0 1 Output Yes NOT RECOMMENDED.
Output low (sink) and internal pull-up active. Sources
current through the internal pull-up resistor and consumes
power constantly
1 1 0 Output No Output high (source)
1 1 1 Output Yes Output high (source) and internal pull-up active
Port pins are tri-stated when a reset condition becomes active, even when no clocks are running.
12.2.2. Toggling the Pin
Writing a '1' to PINxn toggles the value of PORTxn, independent on the value of DDRxn. The SBI
instruction can be used to toggle one single bit in a port.
12.2.3. Break-Before-Make Switching
In Break-Before-Make mode, switching the DDRxn bit from input to output introduces an immediate tri-
state period lasting one system clock cycle, as indicated in the figure below. For example, if the system
clock is 4 MHz and the DDRxn is written to make an output, an immediate tri-state period of 250 ns is
introduced before the value of PORTxn is seen on the port pin.
To avoid glitches it is recommended that the maximum DDRxn toggle frequency is two system clock
cycles. The Break-Before-Make mode applies to the entire port and it is activated by the BBMx bit. For
more details, see PORTCR – Port Control Register.
When switching the DDRxn bit from output to input no immediate tri-state period is introduced.
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Figure 12-3 Switching Between Input and Output in Break-Before-Make-Mode
out DDRx, r16 nop
0x02 0x01
SYSTEM CLK
INSTRUCTIONS
DDRx
intermediate tri-state cycle
out DDRx, r17
0x55
PORTx
0x01
intermediate tri-state cycle
Px0
Px1
tri-state
tri-statetri-state
0x01
r17
0x02
r16
Related Links
PORTCR on page 76
12.2.4. Reading the Pin Value
Independent of the setting of Data Direction bit DDxn, the port pin can be read through the PINxn
Register bit. As shown in Figure 12-2 General Digital I/O on page 66, the PINxn Register bit and the
preceding latch constitute a synchronizer. This is needed to avoid metastability if the physical pin changes
value near the edge of the internal clock, but it also introduces a delay. The following figure shows a
timing diagram of the synchronization when reading an externally applied pin value. The maximum and
minimum propagation delays are denoted tpd,max and tpd,min respectively.
Figure 12-4 Synchronization when Reading an Externally Applied Pin value
XXX in r17, PINx
0x00 0xFF
INSTRUCTIONS
SYNC LATCH
PINxn
r17
XXX
SYSTEM CLK
tpd, max
tpd, min
Consider the clock period starting shortly after the first falling edge of the system clock. The latch is
closed when the clock is low, and goes transparent when the clock is high, as indicated by the shaded
region of the “SYNC LATCH” signal. The signal value is latched when the system clock goes low. It is
clocked into the PINxn Register at the succeeding positive clock edge. As indicated by the two arrows
tpd,max and tpd,min, a single signal transition on the pin will be delayed between ½ and 1½ system clock
period depending upon the time of assertion.
When reading back a software assigned pin value, a nop instruction must be inserted as indicated in the
following figure. The out instruction sets the “SYNC LATCH” signal at the positive edge of the clock. In
this case, the delay tpd through the synchronizer is 1 system clock period.
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Figure 12-5 Synchronization when Reading a Software Assigned Pin Value
out PORTx, r16 nop in r17, PINx
0xFF
0x00 0xFF
SYSTEM CLK
r16
INSTRUCTIONS
SYNC LATCH
PINxn
r17
tpd
12.2.5. Digital Input Enable and Sleep Modes
As shown in the figure of General Digital I/O, the digital input signal can be clamped to ground at the input
of the Schmitt Trigger. The signal denoted SLEEP in the figure, is set by the MCU Sleep Controller in
Power-down mode and Standby mode to avoid high power consumption if some input signals are left
floating, or have an analog signal level close to VCC/2.
SLEEP is overridden for port pins enabled as external interrupt pins. If the external interrupt request is not
enabled, SLEEP is active also for these pins. SLEEP is also overridden by various other alternate
functions as described in Alternate Port Functions section in this chapter.
If a logic high level is present on an asynchronous external interrupt pin configured as “Interrupt on Rising
Edge, Falling Edge, or Any Logic Change on Pin” while the external interrupt is not enabled, the
corresponding External Interrupt Flag will be set when resuming from the above mentioned Sleep mode,
as the clamping in these sleep mode produces the requested logic change.
12.2.6. Unconnected Pins
If some pins are unused, it is recommended to ensure that these pins have a defined level. Even though
most of the digital inputs are disabled in the deep sleep modes as described above, floating inputs should
be avoided to reduce current consumption in all other modes where the digital inputs are enabled (Reset,
Active mode and Idle mode).
The simplest method to ensure a defined level of an unused pin, is to enable the internal pull-up. In this
case, the pull-up will be disabled during reset. If low power consumption during reset is important, it is
recommended to use an external pull-up or pull-down. Connecting unused pins directly to VCC or GND is
not recommended, since this may cause excessive currents if the pin is accidentally configured as an
output.
12.2.7. Program Example
The following code example shows how to set port B pin 0 high, pin 1 low, and define the port pins from 2
to 3 as input with a pull-up assigned to port pin 2. The resulting pin values are read back again, but as
previously discussed, a nop instruction is included to be able to read back the value recently assigned to
some of the pins.
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Assembly Code Example
...
; Define pull-ups and set outputs high
; Define directions for port pins
ldi r16,(1<<PUEB2)
ldi r17,(1<<PB0)
ldi r18,(1<<DDB1)|(1<<DDB0)
out PUEB,r16
out PORTB,r17
out DDRB,r18
; Insert nop for synchronization
nop
; Read port pins
in r16,PINB
...
Related Links
About Code Examples on page 14
12.2.8. Alternate Port Functions
Most port pins have alternate functions in addition to being general digital I/Os. The following figure
shows how the port pin control signals from the simplified in the figure of Ports as General Digital I/O can
be overridden by alternate functions. The overriding signals may not be present in all port pins, but the
figure serves as a generic description applicable to all port pins in the AVR microcontroller family.
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Figure 12-6 Alternate Port Functions
clk
RPx
RRx WRx
RDx
WDx
SYNCHRONIZER
WDx: WRITE DDRx
WRx: WRITE PORTx
RRx: READ PORTx REGISTER
RPx: READ PORTx PIN
REx: READ PUEx
WEx: WRITE PUEx
clkI/O: I/O CLOCK
RDx: READ DDRx
D
L
Q
Q
SET
CLR
0
1
0
1
0
1
DIxn
AIOxn
DIEOExn
PVOVxn
PVOExn
DDOVxn
DDOExn
PUOExn
PUOVxn
PUOExn: Pxn PULL-UP OVERRIDE ENABLE
PUOVxn: Pxn PULL-UP OVERRIDE VALUE
DDOExn: Pxn DATA DIRECTION OVERRIDE ENABLE
DDOVxn: Pxn DATA DIRECTION OVERRIDE VALUE
PVOExn: Pxn PORT VALUE OVERRIDE ENABLE
PVOVxn: Pxn PORT VALUE OVERRIDE VALUE
DIxn: DIGITAL INPUT PIN n ON PORTx
AIOxn: ANALOG INPUT/OUTPUT PIN n ON PORTx
RESET
RESET
Q
Q D
CLR
Q
Q D
CLR
Q
QD
CLR
PINxn
PORTxn
DDxn
DATA BUS
0
1
DIEOVxn
SLEEP
DIEOExn: Pxn DIGITAL INPUT-ENABLE OVERRIDE ENABLE
DIEOVxn: Pxn DIGITAL INPUT-ENABLE OVERRIDE VALUE
SLEEP: SLEEP CONTROL
Pxn
I/O
0
1
PTOExn
PTOExn: Pxn, PORT TOGGLE OVERRIDE ENABLE
WPx: WRITE PINx
WPx
WEx
REx
RESET
Q
Q D
CLR
PUExn
Note: 1. WEx, WRx, WPx, WDx, REx, RRx, RPx, and RDx are common to all pins within the same port.
clkI/O and SLEEP are common to all ports. All other signals are unique for each pin.
The following table summarizes the function of the overriding signals. The pin and port indexes from
previous figure are not shown in the succeeding tables. The overriding signals are generated internally in
the modules having the alternate function.
Table 12-2 Generic Description of Overriding Signals for Alternate Functions
Signal Name Full Name Description
PUOE Pull-up Override
Enable
If this signal is set, the pull-up enable is controlled by the PUOV signal.
If this signal is cleared, the pull-up is enabled when PUExn = 0b1.
PUOV Pull-up Override Value If PUOE is set, the pull-up is enabled/disabled when PUOV is set/
cleared, regardless of the setting of the PUExn Register bit.
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Signal Name Full Name Description
DDOE Data Direction
Override Enable
If this signal is set, the Output Driver Enable is controlled by the DDOV
signal. If this signal is cleared, the Output driver is enabled by the DDxn
Register bit.
DDOV Data Direction
Override Value
If DDOE is set, the Output Driver is enabled/disabled when DDOV is
set/cleared, regardless of the setting of the DDxn Register bit.
PVOE Port Value Override
Enable
If this signal is set and the Output Driver is enabled, the port value is
controlled by the PVOV signal. If PVOE is cleared, and the Output
Driver is enabled, the port Value is controlled by the PORTxn Register
bit.
PVOV Port Value Override
Value
If PVOE is set, the port value is set to PVOV, regardless of the setting of
the PORTxn Register bit.
PTOE Port Toggle Override
Enable
If PTOE is set, the PORTxn Register bit is inverted.
DIEOE Digital Input Enable
Override Enable
If this bit is set, the Digital Input Enable is controlled by the DIEOV
signal. If this signal is cleared, the Digital Input Enable is determined by
MCU state (Normal mode, sleep mode).
DIEOV Digital Input Enable
Override Value
If DIEOE is set, the Digital Input is enabled/disabled when DIEOV is set/
cleared, regardless of the MCU state (Normal mode, sleep mode).
DI Digital Input This is the Digital Input to alternate functions. In the figure, the signal is
connected to the output of the Schmitt Trigger but before the
synchronizer. Unless the Digital Input is used as a clock source, the
module with the alternate function will use its own synchronizer.
AIO Analog Input/Output This is the Analog Input/output to/from alternate functions. The signal is
connected directly to the pad, and can be used bi-directionally.
The following subsections shortly describe the alternate functions for each port, and relate the overriding
signals to the alternate function. Refer to the alternate function description for further details.
12.2.8.1. Alternate Functions of Port B
The Port B pins with alternate functions are shown in the table below:
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Table 12-3 Port B Pins Alternate Functions
Port Pin Alternate Functions
PB[0] ADC0: ADC Input Channel 0
AIN0: Analog Comparator, Positive Input
OC0A: Timer/Counter0 Compare Match A Output
PCINT0: Pin Change Interrupt 0, Source 0
TPIDATA: Serial Programming Data
PB[1] ADC1: ADC Input Channel 1
AIN1: Analog Comparator, Negative Input
CLKI: External Clock
ICP0: Timer/Counter0 Input Capture Input
OC0B: Timer/Counter0 Compare Match B Output
PCINT1: Pin Change Interrupt 0, Source 1
TPICLK: Serial Programming Clock
PB[2] ADC2: ADC Input Channel 2
CLKO: System Clock Output
INT0: External Interrupt 0 Source
PCINT2: Pin Change Interrupt 0, Source 2
T0: Timer/Counter0 Clock Source
PB[3] ADC3: ADC Input Channel 3
PCINT3: Pin Change Interrupt 0, Source 3
RESET: Reset Pin
The alternate pin configuration is as follows:
•PB[0] – ADC0/AIN0/OC0A/PCINT0/TPIDATA
–ADC0: Analog to Digital Converter, Channel 0 (ATtiny5/10, only)
–AIN0: Analog Comparator Positive Input. Configure the port pin as input with the internal pull-
up switched off to avoid the digital port function from interfering with the function of the Analog
Comparator.
–OC0A, Output Compare Match output: The PB0 pin can serve as an external output for the
Timer/Counter0 Compare Match A. The pin has to be configured as an output (DDB0 set
(one)) to serve this function. This is also the output pin for the PWM mode timer function.
–PCINT0: Pin Change Interrupt source 0. The PB0 pin can serve as an external interrupt
source for pin change interrupt 0.
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–TPIDATA: Serial Programming Data.
•PB[1] – ADC1/AIN1/CLKI/ICP0/OC0B/PCINT1/TPICLK
–ADC1: Analog to Digital Converter, Channel 1 (ATtiny5/10, only)
–AIN1: Analog Comparator Negative Input. Configure the port pin as input with the internal
pull-up switched off to avoid the digital port function from interfering with the function of the
Analog Comparator.
–CLKI: External Clock.
–ICP0: Input Capture Pin. The PB1 pin can act as an Input Capture pin for Timer/Counter0.
–OC0B: Output Compare Match output: The PB1 pin can serve as an external output for the
Timer/Counter0 Compare Match B. The PB1 pin has to be configured as an output (DDB1 set
(one)) to serve this function. The OC0B pin is also the output pin for the PWM mode timer
function.
–PCINT1: Pin Change Interrupt source 1. The PB1 pin can serve as an external interrupt
source for pin change interrupt 0.
–TPICLK: Serial Programming Clock.
•PB[2] – ADC2/CLKO/INT0/PCINT2/T0
–ADC2: Analog to Digital Converter, Channel 2 (ATtiny5/10, only)
–CLKO: System Clock Output. The system clock can be output on pin PB2. The system clock
will be output if CKOUT bit is programmed, regardless of the PORTB2 and DDB2 settings.
–INT0: External Interrupt Request 0
–PCINT2: Pin Change Interrupt source 2. The PB2 pin can serve as an external interrupt
source for pin change interrupt 0.
–T0: Timer/Counter0 counter source.
•PB[3] – ADC3/PCINT3/RESET
–ADC3: Analog to Digital Converter, Channel 3 (ATtiny5/10, only)
–PCINT3: Pin Change Interrupt source 3. The PB3 pin can serve as an external interrupt
source for pin change interrupt 0.
–RESET:
The following tables relate the alternate functions of Port B to the overriding signals shown in the figure of
Alternate Port Functions.
Table 12-4 Overriding Signals for Alternate Functions in PB[3:2]
Signal
Name
PB3/ADC3/RESET/PCINT3 PB2/ADC2/INT0/T0/CLKO/PCINT2
PUOE RSTDISBL(1) CKOUT(2)
PUOV 1 0
DDOE RSTDISBL(1) CKOUT(2)
DDOV 0 1
PVOE 0 CKOUT(2)
PVOV 0 (system clock)
PTOE 0 0
DIEOE RSTDISBL(1) + (PCINT3 • PCIE0) + ADC3D (PCINT2 • PCIE0) + ADC2D + INT0
DIEOV RSTDISBL • PCINT3 • PCIE0 (PCINT2 • PCIE0) + INT0
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Signal
Name
PB3/ADC3/RESET/PCINT3 PB2/ADC2/INT0/T0/CLKO/PCINT2
DI PCINT3 Input INT0/T0/PCINT2 Input
AIO ADC3 Input ADC2 Input
Note:
1. RSTDISBL is 1 when the configuration bit is “0” (Programmed).
2. CKOUT is 1 when the configuration bit is “0” (Programmed).
Table 12-5 Overriding Signals for Alternate Functions in PB[1:0]
Signal
Name
PB1/ADC1/AIN1/OC0B/CLKI/ICP0/PCINT1 PB0/ADC0/AIN0/OC0A/PCINT0
PUOE EXT_CLOCK(1) 0
PUOV 0 0
DDOE EXT_CLOCK(1) 0
DDOV 0 0
PVOE EXT_CLOCK(1)+ OC0B Enable OC0A Enable
PVOV EXT_CLOCK(1)• OC0B OC0A
PTOE 0 0
DIEOE EXT_CLOCK(1)+ (PCINT1 • PCIE0) + ADC1D (PCINT0 • PCIE0) + ADC0D
DIEOV EXT_CLOCK(1)• PWR_DOWN) + (EXT_CLOCK(1) • PCINT1 •
PCIE0)
PCINT0 • PCIE0
DI CLOCK/ICP0/PCINT1 Input PCINT0 Input
AIO ADC1/Analog Comparator Negative Input ADC0/Analog Comparator Positive Input
Note:
1. EXT_CLOCK is 1 when external clock is selected as main clock.
12.3. Register Description
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12.3.1. Port Control Register
Name: PORTCR
Offset: 0x0C
Reset: 0
Property:
Bit 7 6 5 4 3 2 1 0
BBMB
Access R/W
Reset 0
Bit 1 – BBMB: Break-Before-Make Mode Enable
When this bit is set the Break-Before-Make mode is activated for the entire Port B. The intermediate tri-
state cycle is then inserted when writing DDRxn to make an output.
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12.3.2. Port B Pull-up Enable Control Register
Name: PUEB
Offset: 0x03
Reset: 0
Property:
Bit 7 6 5 4 3 2 1 0
PUEB3 PUEB2 PUEB1 PUEB0
Access R/W R/W R/W R/W
Reset 0 0 0 0
Bits 3:0 – PUEBn: Port B Input Pins Address [n = 3:0]
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12.3.3. Port B Data Register
Name: PORTB
Offset: 0x02
Reset: 0x00
Property:
Bit 7 6 5 4 3 2 1 0
PORTB3 PORTB2 PORTB1 PORTB0
Access R/W R/W R/W R/W
Reset 0 0 0 0
Bits 3:0 – PORTBn: Port B Data [n = 3:0]
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12.3.4. Port B Data Direction Register
Name: DDRB
Offset: 0x01
Reset: 0
Property:
Bit 7 6 5 4 3 2 1 0
DDRB3 DDRB2 DDRB1 DDRB0
Access R/W R/W R/W R/W
Reset 0 0 0 0
Bits 3:0 – DDRBn: Port B Input Pins Address [n = 3:0]
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12.3.5. Port B Input Pins Address
Name: PINB
Offset: 0x00
Reset: N/A
Property:
Bit 7 6 5 4 3 2 1 0
PINB3 PINB2 PINB1 PINB0
Access R/W R/W R/W R/W
Reset x x x x
Bits 3:0 – PINBn: Port B Input Pins Address [n = 3:0]
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13. 16-bit Timer/Counter0 with PWM
13.1. Features
•True 16-bit Design (i.e., allows 16-bit PWM)
•Two independent Output Compare Units
•Double Buffered Output Compare Registers
•One Input Capture Unit
•Input Capture Noise Canceler
•Clear Timer on Compare Match (Auto Reload)
•Glitch-free, Phase Correct Pulse Width Modulator (PWM)
•Variable PWM Period
•Frequency Generator
•External Event Counter
•Four independent interrupt Sources (TOV0, OCF0A, OCF0B, and ICF0)
13.2. Overview
The 16-bit Timer/Counter unit allows accurate program execution timing (event management), wave
generation, and signal timing measurement.
A block diagram of the 16-bit Timer/Counter is shown below. CPU accessible I/O Registers, including I/O
bits and I/O pins, are shown in bold. The device-specific I/O Register and bit locations are listed in
Register Description on page 102. For the actual placement of I/O pins, refer to the Pin Configurations
description.
The Power Reduction TC0 bit in the Power Reduction Register (PRR.PRTIM0) must be written to zero to
enable the Timer/Counter0 module.
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Figure 13-1 16-bit Timer/Counter Block Diagram(1)
Clock Select
Timer/Counter
DATA BUS
OCRnA
OCRnB
ICRn
=
=
TCNTn
Waveform
Generation
Waveform
Generation
OCnA
OCnB
Noise
Canceler
ICPn
=
Fixed
TOP
Values
Edge
Detector
Control Logic
= 0
TOP BOTTOM
Count
Clear
Direction
TOVn
(Int.Req.)
OCnA
(Int.Req.)
OCnB
(Int.Req.)
ICFn (Int.Req.)
TCCRnA TCCRnB
( From Analog
Comparator Ouput )
Tn
Edge
Detector
( From Prescaler )
clkTn
Note: The “n” in the register and bit names indicates the device number (n = 0 for Timer/Counter 0)
See the related links for actual pin placement.
13.2.1. Definitions
Many register and bit references in this section are written in general form:
•n represents the Timer/Counter number
•x=A,B represents the Output Compare Unit A or B
However, when using the register or bit definitions in a program, the precise form must be used, i.e.,
TCNT0 for accessing Timer/Counter0 counter value.
The following definitions are used throughout the section:
Table 13-1 Definitions
Constant Description
BOTTOM The counter reaches the BOTTOM when it becomes zero (0x0 for 8-bit counters, or 0x00 for
16-bit counters).
MAX The counter reaches its Maximum when it becomes 0xF (decimal 15, for 8-bit counters) or
0xFF (decimal 255, for 16-bit counters).
TOP The counter reaches the TOP when it becomes equal to the highest value in the count
sequence. The TOP value can be assigned to be the fixed value MAX or the value stored in
the OCR0A Register. The assignment is dependent on the mode of operation.
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13.2.2. Registers
The Timer/Counter (TCNT0), Output Compare Registers (OCR0A/B), and Input Capture Register (ICR0)
are all 16-bit registers. Special procedures must be followed when accessing the 16-bit registers. These
procedures are described in section Accessing 16-bit Registers.
The Timer/Counter Control Registers (TCCR0A/B) are 8-bit registers and have no CPU access
restrictions. Interrupt requests (abbreviated to Int.Req. in the block diagram) signals are all visible in the
Timer Interrupt Flag Register (TIFR0). All interrupts are individually masked with the Timer Interrupt Mask
Register (TIMSK0). TIFR0 and TIMSK0 are not shown in the figure.
The Timer/Counter can be clocked internally, via the prescaler, or by an external clock source on the T0
pin. The Clock Select logic block controls which clock source and edge the Timer/Counter uses to
increment (or decrement) its value. The Timer/Counter is inactive when no clock source is selected. The
output from the Clock Select logic is referred to as the timer clock (clkT0).
The double buffered Output Compare Registers (OCR0A/B) are compared with the Timer/Counter value
at all time. The result of the compare can be used by the Waveform Generator to generate a PWM or
variable frequency output on the Output Compare pin (OC0A/B). See Output Compare Units. The
compare match event will also set the Compare Match Flag (OCF0A/B) which can be used to generate
an Output Compare interrupt request.
The Input Capture Register can capture the Timer/Counter value at a given external (edge triggered)
event on either the Input Capture pin (ICP0) or on the Analog Comparator pins. The Input Capture unit
includes a digital filtering unit (Noise Canceler) for reducing the chance of capturing noise spikes.
The TOP value, or maximum Timer/Counter value, can in some modes of operation be defined by either
the OCR0A Register, the ICR0 Register, or by a set of fixed values. When using OCR0A as TOP value in
a PWM mode, the OCR0A Register can not be used for generating a PWM output. However, the TOP
value will in this case be double buffered allowing the TOP value to be changed in run time. If a fixed TOP
value is required, the ICR0 Register can be used as an alternative, freeing the OCR0A to be used as
PWM output.
Related Links
TCNT0H on page 109
TCNT0L on page 110
OCR0AH on page 111
OCR0AL on page 112
OCR0BH on page 113
OCR0BL on page 114
ICR0H on page 115
ICR0L on page 116
TCCR0A on page 103
TCCR0B on page 106
TIFR0 on page 118
TIMSK0 on page 117
Analog Comparator on page 120
13.3. Accessing 16-bit Registers
The TCNT0, OCR0A/B, and ICR0 are 16-bit registers that can be accessed by the AVR CPU via the 8-bit
data bus. The 16-bit register must be accessed byte-wise, using two read or write operations. Each 16-bit
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timer has a single 8-bit TEMP register for temporary storing of the high byte of the 16-bit access. The
same temporary register is shared between all 16-bit registers within each 16-bit timer.
Accessing the low byte triggers the 16-bit read or write operation: When the low byte of a 16-bit register is
written by the CPU, the high byte that is currently stored in TEMP and the low byte being written are both
copied into the 16-bit register in the same clock cycle. When the low byte of a 16-bit register is read by
the CPU, the high byte of the 16-bit register is copied into the TEMP register in the same clock cycle as
the low byte is read, and must be read subsequently.
Note: To perform a 16-bit write operation, the high byte must be written before the low byte. For a 16-bit
read, the low byte must be read before the high byte.
Not all 16-bit accesses uses the temporary register for the high byte. Reading the OCR0A/B 16-bit
registers does not involve using the temporary register.
16-bit Access
The following code examples show how to access the 16-bit Timer Registers assuming that no interrupts
updates the temporary register. The same principle can be used directly for accessing the OCR0A/B and
ICR0 Registers. Note that when using C, the compiler handles the 16-bit access.
Assembly Code Example
...
; Set TCNT0 to 0x01FF
ldi r17,0x01
ldi r16,0xFF
out TCNT0H,r17
out TCNT0L,r16
; Read TCNT0 into r17:r16
in r16,TCNT0L
in r17,TCNT0H
...
The assembly code example returns the TCNT0 value in the r17:r16 register pair.
C Code Example
unsigned int i;
...
/* Set TCNT0 to 0x01FF */
TCNT0 = 0x1FF;
/* Read TCNT0 into i */
i = TCNT0;
...
Atomic Read
It is important to notice that accessing 16-bit registers are atomic operations. If an interrupt occurs
between the two instructions accessing the 16-bit register, and the interrupt code updates the temporary
register by accessing the same or any other of the 16-bit Timer Registers, then the result of the access
outside the interrupt will be corrupted. Therefore, when both the main code and the interrupt code update
the temporary register, the main code must disable the interrupts during the 16-bit access.
The following code examples show how to perform an atomic read of the TCNT0 Register contents. A
OCR0A/B or ICR0 Registers can be ready by using the same principle.
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Assembly Code Example
TIM16_ReadTCNT0:
; Save global interrupt flag
in r18,SREG
; Disable interrupts
cli
; Read TCNT0 into r17:r16
in r16,TCNT0L
in r17,TCNT0H
; Restore global interrupt flag
out SREG,r18
ret
The assembly code example returns the TCNT0 value in the r17:r16 register pair.
C Code Example
unsigned int TIM16_ReadTCNT0( void )
{
unsigned char sreg;
unsigned int i;
/* Save global interrupt flag */
sreg = SREG;
/* Disable interrupts */
_CLI();
/* Read TCNT0 into i */
i = TCNT0;
/* Restore global interrupt flag */
SREG = sreg;
return i;
}
Atomic Write
The following code examples show how to do an atomic write of the TCNT0 Register contents. Writing
any of the OCR0A/B or ICR0 Registers can be done by using the same principle.
Assembly Code Example
TIM16_WriteTCNT0:
; Save global interrupt flag
in r18,SREG
; Disable interrupts
cli
; Set TCNT0 to r17:r16
out TCNT0H,r17
out TCNT0L,r16
; Restore global interrupt flag
out SREG,r18
ret
The assembly code example requires that the r17:r16 register pair contains the value to
be written to TCNT0.
C Code Example
void TIM16_WriteTCNT0( unsigned int i )
{
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unsigned char sreg;
unsigned int i;
/* Save global interrupt flag */
sreg = SREG;
/* Disable interrupts */
_CLI();
/* Set TCNT0 to i */
TCNT0 = i;
/* Restore global interrupt flag */
SREG = sreg;
}
13.3.1. Reusing the Temporary High Byte Register
If writing to more than one 16-bit register where the high byte is the same for all registers written, the high
byte only needs to be written once to TEMP. However, the same rule of atomic operation described
previously also applies in this case.
13.4. Timer/Counter Clock Sources
The Timer/Counter can be clocked by an internal or an external clock source. The clock source is
selected by the Clock Select logic which is controlled by the Clock Select bits in the Timer/Counter control
Register B (TCCR0B.CS0[2:0]).
13.4.1. Internal Clock Source - Prescaler
The Timer/Counter can be clocked directly by the system clock (by setting the TCCR0B.CS0[2:0]=0x1).
This provides the fastest operation, with a maximum Timer/Counter clock frequency equal to system clock
frequency (fCLK_I/O). Alternatively, one of four taps from the prescaler can be used as a clock source. The
prescaled clock has a frequency of either fCLK_I/O/8, fCLK_I/O/64, fCLK_I/O/256, or fCLK_I/O/1024.
Figure 13-2 Prescaler for Timer/Counter0
PS R10
Cle a r
clk
T0
T0
clk
I/O
Synchronization
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13.4.2. Prescaler Reset
The prescaler is free running, i.e., operates independently of the Clock Select logic of the Timer/Counter,
and it is shared by Timer/Counter 0 (T0). Since the prescaler is not affected by the Timer/Counter’s clock
select, the state of the prescaler will have implications for situations where a prescaled clock is used. One
example of prescaling artifacts occurs when the timer is enabled and clocked by the prescaler
(TCCR0B.CS0[2:0] = 2, 3, 4, or 5). The number of system clock cycles from when the timer is enabled to
the first count occurs can be from 1 to N+1 system clock cycles, where N equals the prescaler divisor (8,
64, 256, or 1024).
It is possible to use the prescaler reset for synchronizing the Timer/Counter to program execution.
However, care must be taken if the other Timer/Counter that shares the same prescaler also uses
prescaling. A prescaler reset will affect the prescaler period for all Timer/Counters it is connected to.
13.4.3. External Clock Source
An external clock source applied to the T0 pin can be used as Timer/Counter clock (clkT0). The T0 pin is
sampled once every system clock cycle by the pin synchronization logic. The synchronized (sampled)
signal is then passed through the edge detector. See also the block diagram of the T0 synchronization
and edge detector logic below. The registers are clocked at the positive edge of the internal system clock
(clkI/O). The latch is transparent in the high period of the internal system clock.
The edge detector generates one clkT0 pulse for each positive (CS0[2:0]=0x7) or negative (CS0[2:0]=0x6)
edge it detects.
Figure 13-3 T0 Pin Sampling
Tn_s ync
(To Clock
Select Logic)
Edge De te ctorSynchronization
D QD Q
LE
D Q
Tn
clk
I/O
Note: The “n” indicates the device number (n = 0 for Timer/Counter 0)
The synchronization and edge detector logic introduces a delay of 2.5 to 3.5 system clock cycles from an
edge has been applied to the T0 pin to the counter is updated.
Enabling and disabling of the clock input must be done when T0 has been stable for at least one system
clock cycle, otherwise it is a risk that a false Timer/Counter clock pulse is generated.
Each half period of the external clock applied must be longer than one system clock cycle to ensure
correct sampling. The external clock must be guaranteed to have less than half the system clock
frequency (fExtClk < fclk_I/O/2) given a 50% duty cycle. Since the edge detector uses sampling, the
maximum frequency of an external clock it can detect is half the sampling frequency (Nyquist sampling
theorem). However, due to variation of the system clock frequency and duty cycle caused by the
tolerances of the oscillator source (crystal, resonator, and capacitors), it is recommended that maximum
frequency of an external clock source is less than fclk_I/O/2.5.
An external clock source can not be prescaled.
13.5. Counter Unit
The main part of the 16-bit Timer/Counter is the programmable 16-bit bi-directional counter unit, as shown
in the block diagram:
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Figure 13-4 Counter Unit Block Diagram
TEMP (8-bit)
DATA BUS (8-bit)
TCNTn (16-bit Counter)
TCNTnH (8-bit) TCNTnL (8-bit) Control Logic
Count
Clear
Direction
TOVn
(Int.Req.)
Clock Select
TOP BOTTOM
Tn
Edge
Detector
( From Prescaler )
clkTn
Note: The “n” in the register and bit names indicates the device number (n = 0 for Timer/Counter 0), and
the “x” indicates Output Compare unit (A/B).
Table 13-2 Signal description (internal signals)
Signal Name Description
Count Increment or decrement TCNT0 by 1.
Direction Select between increment and decrement.
Clear Clear TCNT0 (set all bits to zero).
clkT0 Timer/Counter clock.
TOP Signalize that TCNT0 has reached maximum value.
BOTTOM Signalize that TCNT0 has reached minimum value (zero).
The 16-bit counter is mapped into two 8-bit I/O memory locations: Counter High (TCNT0H) containing the
upper eight bits of the counter, and Counter Low (TCNT0L) containing the lower eight bits. The TCNT0H
Register can only be accessed indirectly by the CPU. When the CPU does an access to the TCNT0H I/O
location, the CPU accesses the high byte temporary register (TEMP). The temporary register is updated
with the TCNT0H value when the TCNT0L is read, and TCNT0H is updated with the temporary register
value when TCNT0L is written. This allows the CPU to read or write the entire 16-bit counter value within
one clock cycle via the 8-bit data bus.
Note: That there are special cases when writing to the TCNT0 Register while the counter is counting will
give unpredictable results. These special cases are described in the sections where they are of
importance.
Depending on the selected mode of operation, the counter is cleared, incremented, or decremented at
each timer clock (clkT0). The clock clkT0 can be generated from an external or internal clock source, as
selected by the Clock Select bits in the Timer/Counter0 Control Register B (TCCR0B.CS0[2:0]). When no
clock source is selected (CS0[2:0]=0x0) the timer is stopped. However, the TCNT0 value can be
accessed by the CPU, independent of whether clkT0 is present or not. A CPU write overrides (i.e., has
priority over) all counter clear or count operations.
The counting sequence is determined by the setting of the Waveform Generation mode bits in the Timer/
Counter Control Registers A and B (TCCR0B.WGM0[3:2] and TCCR0A.WGM0[1:0]). There are close
connections between how the counter behaves (counts) and how waveforms are generated on the Output
Compare outputs OC0x. For more details about advanced counting sequences and waveform generation,
see Modes of Operation on page 93.
The Timer/Counter Overflow Flag in the TC0 Interrupt Flag Register (TIFR0.TOV0) is set according to the
mode of operation selected by the WGM0[3:0] bits. TOV0 can be used for generating a CPU interrupt.
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13.6. Input Capture Unit
The Timer/Counter0 incorporates an Input Capture unit that can capture external events and give them a
time-stamp indicating time of occurrence. The external signal indicating an event, or multiple events, can
be applied via the ICP0 pin or alternatively, via the analog-comparator unit. The time-stamps can then be
used to calculate frequency, duty-cycle, and other features of the signal applied. Alternatively the time-
stamps can be used for creating a log of the events.
The Input Capture unit is illustrated by the block diagram below. The elements of the block diagram that
are not directly a part of the Input Capture unit are gray shaded. The lower case “n” in register and bit
names indicates the Timer/Counter number.
Figure 13-5 Input Capture Unit Block Diagram for Timer/Counter0
ICFn (Int.Req.)
Analog
Comparator
WRITE ICRn (16-bit Register)
ICRnH (8-bit)
Noise
Canceler
ICPn
Edge
Detector
TEMP (8-bit)
DATA BUS (8-bit)
ICRnL (8-bit)
TCNTn (16-bit Counter)
TCNTnH (8-bit) TCNTnL (8-bit)
ACIC* ICNC ICES
ACO*
Note: The “n” in the register and bit names indicates the device number (n = 0 for Timer/Counter 0), and
the “x” indicates Output Compare unit (A/B).
Note: Analog comparator can be used for only Timer/Counter0 and not applicable for Timer/Counter3 or
Timer/Counter4.
When a change of the logic level (an event) occurs on the Input Capture pin (ICP0), or alternatively on the
Analog Comparator output (ACO), and this change confirms to the setting of the edge detector, a capture
will be triggered: the 16-bit value of the counter (TCNT0) is written to the Input Capture Register (ICR0).
The Input Capture Flag (ICF0) is set at the same system clock cycle as the TCNT0 value is copied into
the ICR0 Register. If enabled (TIMSK0.ICIE0=1), the Input Capture Flag generates an Input Capture
interrupt. The ICF0 Flag is automatically cleared when the interrupt is executed. Alternatively the ICF0
Flag can be cleared by software by writing '1' to its I/O bit location.
Reading the 16-bit value in the Input Capture Register (ICR0) is done by first reading the low byte
(ICR0L) and then the high byte (ICR0H). When the low byte is read form ICR0L, the high byte is copied
into the high byte temporary register (TEMP). When the CPU reads the ICR0H I/O location it will access
the TEMP Register.
The ICR0 Register can only be written when using a Waveform Generation mode that utilizes the ICR0
Register for defining the counter’s TOP value. In these cases the Waveform Generation mode bits
(WGM0[3:0]) must be set before the TOP value can be written to the ICR0 Register. When writing the
ICR0 Register, the high byte must be written to the ICR0H I/O location before the low byte is written to
ICR0L.
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See also Accessing 16-bit Registers on page 83.
13.6.1. Input Capture Trigger Source
The main trigger source for the Input Capture unit is the Input Capture pin (ICP0). Timer/Counter0 can
alternatively use the Analog Comparator output as trigger source for the Input Capture unit. The Analog
Comparator is selected as trigger source by setting the Analog Comparator Input Capture (ACIC) bit in
the Analog Comparator Control and Status Register (ACSR). Be aware that changing trigger source can
trigger a capture. The Input Capture Flag must therefore be cleared after the change.
Both the Input Capture pin (ICP0) and the Analog Comparator output (ACO) inputs are sampled using the
same technique as for the T0 pin. The edge detector is also identical. However, when the noise canceler
is enabled, additional logic is inserted before the edge detector, which increases the delay by four system
clock cycles. The input of the noise canceler and edge detector is always enabled unless the Timer/
Counter is set in a Waveform Generation mode that uses ICR0 to define TOP.
An Input Capture can be triggered by software by controlling the port of the ICP0 pin.
Related Links
ACSR on page 121
13.6.2. Noise Canceler
The noise canceler improves noise immunity by using a simple digital filtering scheme. The noise
canceler input is monitored over four samples, and all four must be equal for changing the output that in
turn is used by the edge detector.
The noise canceler is enabled by setting the Input Capture Noise Canceler bit in the Timer/Counter
Control Register B (TCCR0B.ICNC0). When enabled, the noise canceler introduces an additional delay of
four system clock cycles between a change applied to the input and the update of the ICR0 Register. The
noise canceler uses the system clock and is therefore not affected by the prescaler.
13.6.3. Using the Input Capture Unit
The main challenge when using the Input Capture unit is to assign enough processor capacity for
handling the incoming events. The time between two events is critical. If the processor has not read the
captured value in the ICR0 Register before the next event occurs, the ICR0 will be overwritten with a new
value. In this case the result of the capture will be incorrect.
When using the Input Capture interrupt, the ICR0 Register should be read as early in the interrupt handler
routine as possible. Even though the Input Capture interrupt has relatively high priority, the maximum
interrupt response time is dependent on the maximum number of clock cycles it takes to handle any of
the other interrupt requests.
Using the Input Capture unit in any mode of operation when the TOP value (resolution) is actively
changed during operation, is not recommended.
Measurement of an external signal’s duty cycle requires that the trigger edge is changed after each
capture. Changing the edge sensing must be done as early as possible after the ICR0 Register has been
read. After a change of the edge, the Input Capture Flag (ICF0) must be cleared by software (writing a
logical one to the I/O bit location). For measuring frequency only, the clearing of the ICF0 Flag is not
required (if an interrupt handler is used).
13.7. Output Compare Units
The 16-bit comparator continuously compares TCNT0 with the Output Compare Register (OCR0x). If
TCNT equals OCR0x the comparator signals a match. A match will set the Output Compare Flag
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(OCF0x) at the next timer clock cycle. If enabled (TIMSK0.OCIE0x = 1), the Output Compare Flag
generates an Output Compare interrupt. The OCF0x Flag is automatically cleared when the interrupt is
executed. Alternatively the OCF0x Flag can be cleared by software by writing a logical one to its I/O bit
location. The Waveform Generator uses the match signal to generate an output according to operating
mode set by the Waveform Generation mode (WGM0[3:0]) bits and Compare Output mode (COM0x[1:0])
bits. The TOP and BOTTOM signals are used by the Waveform Generator for handling the special cases
of the extreme values in some modes of operation, see Modes of Operation on page 93.
A special feature of Output Compare unit A allows it to define the Timer/Counter TOP value (i.e., counter
resolution). In addition to the counter resolution, the TOP value defines the period time for waveforms
generated by the Waveform Generator.
Below is a block diagram of the Output Compare unit. The elements of the block diagram that are not
directly a part of the Output Compare unit are gray shaded.
Figure 13-6 Output Compare Unit, Block Diagram
OCFnx (Int.Req.)
= (16-bit Comparator )
OCRnx Buffer (16-bit Register)
OCRnxH Buf. (8-bit)
OCnx
TEMP (8-bit)
DATA BUS (8-bit)
OCRnxL Buf. (8-bit)
TCNTn (16-bit Counter)
TCNTnH (8-bit) TCNTnL (8-bit)
COMnx1:0WGMn3:0
OCRnx (16-bit Register)
OCRnxH (8-bit) OCRnxL (8-bit)
Waveform Generator
TOP
BOTTOM
Note: The “n” in the register and bit names indicates the device number (n = 0 for Timer/Counter 0), and
the “x” indicates Output Compare unit (A/B).
The OCR0x Register is double buffered when using any of the twelve Pulse Width Modulation (PWM)
modes. For the Normal and Clear Timer on Compare (CTC) modes of operation, the double buffering is
disabled. The double buffering synchronizes the update of the OCR0x Compare Register to either TOP or
BOTTOM of the counting sequence. The synchronization prevents the occurrence of odd-length, non-
symmetrical PWM pulses, thereby making the output glitch-free.
When double buffering is enabled, the CPU has access to the OCR0x Buffer Register. When double
buffering is disabled, the CPU will access the OCR0x directly.
The content of the OCR0x (Buffer or Compare) Register is only changed by a write operation (the Timer/
Counter does not update this register automatically as the TCNT0 and ICR0 Register). Therefore OCR0x
is not read via the high byte temporary register (TEMP). However, it is good practice to read the low byte
first as when accessing other 16-bit registers. Writing the OCR0x Registers must be done via the TEMP
Register since the compare of all 16 bits is done continuously. The high byte (OCR0xH) has to be written
first. When the high byte I/O location is written by the CPU, the TEMP Register will be updated by the
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value written. Then when the low byte (OCR0xL) is written to the lower eight bits, the high byte will be
copied into the upper 8-bits of either the OCR0x buffer or OCR0x Compare Register in the same system
clock cycle.
For more information of how to access the 16-bit registers refer to Accessing 16-bit Registers on page 83.
13.7.1. Force Output Compare
In non-PWM waveform generation modes, the match output of the comparator can be forced by writing a
'1' to the Force Output Compare (TCCR0C.FOC0x) bit. Forcing compare match will not set the OCF0x
Flag or reload/clear the timer, but the OC0x pin will be updated as if a real compare match had occurred
(the TCCR0A.COM0x[1:0] bits define whether the OC0x pin is set, cleared or toggled).
13.7.2. Compare Match Blocking by TCNT0 Write
All CPU write operations to the TCNT0 Register will block any compare match that occur in the next timer
clock cycle, even when the timer is stopped. This feature allows OCR0x to be initialized to the same value
as TCNT0 without triggering an interrupt when the Timer/Counter clock is enabled.
13.7.3. Using the Output Compare Unit
Since writing TCNT0 in any mode of operation will block all compare matches for one timer clock cycle,
there are risks involved when changing TCNT0 when using the Output Compare Unit, independently of
whether the Timer/Counter is running or not. If the value written to TCNT0 equals the OCR0x value, the
compare match will be missed, resulting in incorrect waveform generation. Similarly, do not write the
TCNT0 value equal to BOTTOM when the counter is down counting.
The setup of the OC0x should be performed before setting the Data Direction Register for the port pin to
output. The easiest way of setting the OC0x value is to use the Force Output Compare (FOC0x) strobe
bits in Normal mode. The OC0x Registers keep their values even when changing between Waveform
Generation modes.
Be aware that the TCCR0A.COM0x[1:0] bits are not double buffered together with the compare value.
Changing the TCCR0A.COM0x[1:0] bits will take effect immediately.
13.8. Compare Match Output Unit
The Compare Output mode bits in the Timer/Counter Control Register A (TCCR0A.COM0x) have two
functions:
•The Waveform Generator uses the COM0x bits for defining the Output Compare (OC0x) register
state at the next compare match.
•The COM0x bits control the OC0x pin output source
The figure below shows a simplified schematic of the logic affected by COM0x. The I/O Registers, I/O
bits, and I/O pins in the figure are shown in bold. Only the parts of the general I/O port control registers
that are affected by the COM0x bits are shown, namely PORT and DDR.
On system reset the OC0x Register is reset to 0x00.
Note: 'OC0x state' is always referring to internal OC0x registers, not the OC0x pin.
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Figure 13-7 Compare Match Output Unit, Schematic
PORT
DDR
D Q
D Q
OCnx
Pin
OCnx
D Q
Waveform
Generator
COMnx1
COMnx0
0
1
DATA BUS
FOCn
clkI/O
Note: The “n” in the register and bit names indicates the device number (n = 0 for Timer/Counter 0), and
the “x” indicates Output Compare unit (A/B).
The general I/O port function is overridden by the Output Compare (OC0x) from the Waveform Generator
if either of the COM0x[1:0] bits are set. However, the OC0x pin direction (input or output) is still controlled
by the Data Direction Register (DDR) for the port pin. The In the Data Direction Register, the bit for the
OC0x pin (DDR.OC0x) must be set as output before the OC0x value is visible on the pin. The port
override function is independent of the Waveform Generation mode.
The design of the Output Compare pin logic allows initialization of the OC0x register state before the
output is enabled. Some TCCR0A.COM0x[1:0] bit settings are reserved for certain modes of operation.
The TCCR0A.COM0x[1:0] bits have no effect on the Input Capture unit.
13.8.1. Compare Output Mode and Waveform Generation
The Waveform Generator uses the TCCR0A.COM0x[1:0] bits differently in Normal, CTC, and PWM
modes. For all modes, setting the TCCR0A.COM0x[1:0]=0x0 tells the Waveform Generator that no action
on the OC0x Register is to be performed on the next compare match. Refer also to the descriptions of the
output modes.
A change of the TCCR0A.COM0x[1:0] bits state will have effect at the first compare match after the bits
are written. For non-PWM modes, the action can be forced to have immediate effect by using the
TCCR0C.FOC0x strobe bits.
13.9. Modes of Operation
The mode of operation, i.e., the behavior of the Timer/Counter and the Output Compare pins, is defined
by the combination of the Waveform Generation mode (WGM0[3:0]) and Compare Output mode
(TCCR0A.COM0x[1:0]) bits. The Compare Output mode bits do not affect the counting sequence, while
the Waveform Generation mode bits do. The TCCR0A.COM0x[1:0] bits control whether the PWM output
generated should be inverted or not (inverted or non-inverted PWM). For non-PWM modes the
TCCR0A.COM0x[1:0] bits control whether the output should be set, cleared, or toggle at a compare
match.
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13.9.1. Normal Mode
The simplest mode of operation is the Normal mode (WGM0[3:0]=0x0). In this mode the counting
direction is always up (incrementing), and no counter clear is performed. The counter simply overruns
when it passes its maximum 16-bit value (MAX=0xFFFF) and then restarts from BOTTOM=0x0000. In
normal operation the Timer/Counter Overflow Flag (TOV0) will be set in the same timer clock cycle as the
TCNT0 becomes zero. In this case, the TOV0 Flag in behaves like a 17th bit, except that it is only set, not
cleared. However, combined with the timer overflow interrupt that automatically clears the TOV0 Flag, the
timer resolution can be increased by software. There are no special cases to consider in the Normal
mode, a new counter value can be written anytime.
The Input Capture unit is easy to use in Normal mode. However, observe that the maximum interval
between the external events must not exceed the resolution of the counter. If the interval between events
are too long, the timer overflow interrupt or the prescaler must be used to extend the resolution for the
capture unit.
The Output Compare units can be used to generate interrupts at some given time. Using the Output
Compare to generate waveforms in Normal mode is not recommended, since this will occupy too much of
the CPU time.
13.9.2. Clear Timer on Compare Match (CTC) Mode
In Clear Timer on Compare or CTC modes (mode 4 or 12, WGM0[3:0]=0x4 or 0xC), the OCR0A or ICRn
registers are used to manipulate the counter resolution: the counter is cleared to ZERO when the counter
value (TCNT0) matches either the OCR0A (if WGM0[3:0]=0x4) or the ICR0 (WGM0[3:0]=0xC). The
OCR0A or ICR0 define the top value for the counter, hence also its resolution. This mode allows greater
control of the compare match output frequency. It also simplifies the operation of counting external
events.
The timing diagram for the CTC mode is shown below. The counter value (TCNT0) increases until a
compare match occurs with either OCR0A or ICR0, and then TCNT0 is cleared.
Figure 13-8 CTC Mode, Timing Diagram
TCNTn
OCnA
(Toggle)
OCnA Interrupt Flag Set
or ICFn Interrupt Flag Set
(Interrupt on TOP)
1 4
Period 2 3
(COMnA1:0 = 1)
Note: The “n” in the register and bit names indicates the device number (n = 0 for Timer/Counter 0), and
the “x” indicates Output Compare unit (A/B).
An interrupt can be generated at each time the counter value reaches the TOP value by either using the
OCF0A or ICF0 Flag, depending on the actual CTC mode. If the interrupt is enabled, the interrupt handler
routine can be used for updating the TOP value.
Note: Changing TOP to a value close to BOTTOM while the counter is running must be done with care,
since the CTC mode does not provide double buffering. If the new value written to OCR0A is lower than
the current value of TCNT0, the counter will miss the compare match. The counter will then count to its
maximum value (0xFF for a 8-bit counter, 0xFFFF for a 16-bit counter) and wrap around starting at 0x00
before the compare match will occur.
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In many cases this feature is not desirable. An alternative will then be to use the Fast PWM mode using
OCR0A for defining TOP (WGM0[3:0]=0xF), since the OCR0A then will be double buffered.
For generating a waveform output in CTC mode, the OC0A output can be set to toggle its logical level on
each compare match by setting the Compare Output mode bits to toggle mode (COM0A[1:0]=0x1). The
OC0A value will not be visible on the port pin unless the data direction for the pin is set to output
(DDR_OC0A=1). The waveform generated will have a maximum frequency of fOC0A = fclk_I/O/2 when
OCR0A is set to ZERO (0x0000). The waveform frequency is defined by the following equation:
OCnA =clk_I/O
2 1 + OCRnA
Note:
•The “n” in the register and bit names indicates the device number (n = 0 for Timer/Counter 0).
•N represents the prescaler factor (1, 8, 64, 256, or 1024).
As for the Normal mode of operation, the Timer Counter TOV0 Flag is set in the same timer clock cycle
that the counter counts from MAX to 0x0000.
13.9.3. Fast PWM Mode
The Fast Pulse Width Modulation or Fast PWM modes (modes 5, 6, 7, 14,and 15, WGM0[3:0]= 0x5, 0x6,
0x7, 0xE, 0xF) provide a high frequency PWM waveform generation option. The Fast PWM differs from
the other PWM options by its single-slope operation. The counter counts from BOTTOM to TOP then
restarts from BOTTOM.
In non-inverting Compare Output mode, the Output Compare (OC0x) is cleared on the compare match
between TCNT0 and OCR0x, and set at BOTTOM. In inverting Compare Output mode output is set on
compare match and cleared at BOTTOM. Due to the single-slope operation, the operating frequency of
the Fast PWM mode can be twice as high as the phase correct and phase and frequency correct PWM
modes that use dual-slope operation. This high frequency makes the Fast PWM mode well suited for
power regulation, rectification, and DAC applications. High frequency allows physically small sized
external components (coils, capacitors), hence reduces total system cost.
The PWM resolution for Fast PWM can be fixed to 8-, 9-, or 10-bit, or defined by either ICR0 or OCR0A.
The minimum resolution allowed is 2-bit (ICR0 or OCR0A register set to 0x0003), and the maximum
resolution is 16-bit (ICR0 or OCR0A registers set to MAX). The PWM resolution in bits can be calculated
by using the following equation:
FPWM =log TOP+1
log 2
In Fast PWM mode the counter is incremented until the counter value matches either one of the fixed
values 0x00FF, 0x01FF, or 0x03FF (WGM0[3:0] = 0x5, 0x6, or 0x7), the value in ICR0 (WGM0[3:0]=0xE),
or the value in OCR0A (WGM0[3:0]=0xF). The counter is then cleared at the following timer clock cycle.
The timing diagram for the Fast PWM mode using OCR0A or ICR0 to define TOP is shown below. The
TCNT0 value is in the timing diagram shown as a histogram for illustrating the single-slope operation. The
diagram includes non-inverted and inverted PWM outputs. The small horizontal lines on the TCNT0
slopes mark compare matches between OCR0x and TCNT0. The OC0x Interrupt Flag will be set when a
compare match occurs.
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Figure 13-9 Fast PWM Mode, Timing Diagram
TCNTn
OCRnx/TOP Update and
TOVn Interrupt Flag Set and
OCnA Interrupt Flag Set
or ICFn Interrupt Flag Set
(Interrupt on TOP)
1 7
Period 2 3 4 5 6 8
OCnx
OCnx
(COMnx1:0 = 2)
(COMnx1:0 = 3)
Note: The “n” in the register and bit names indicates the device number (n = 0 for Timer/Counter 0), and
the “x” indicates Output Compare unit (A/B).
The Timer/Counter Overflow Flag (TOV0) is set each time the counter reaches TOP. In addition, when
either OCR0A or ICR0 is used for defining the TOP value, the OC0A or ICF0 Flag is set at the same timer
clock cycle TOV0 is set. If one of the interrupts are enabled, the interrupt handler routine can be used for
updating the TOP and compare values.
When changing the TOP value the program must ensure that the new TOP value is higher or equal to the
value of all of the Compare Registers. If the TOP value is lower than any of the Compare Registers, a
compare match will never occur between the TCNT0 and the OCR0x. Note that when using fixed TOP
values the unused bits are masked to zero when any of the OCR0x Registers are written.
The procedure for updating ICR0 differs from updating OCR0A when used for defining the TOP value.
The ICR0 Register is not double buffered. This means that if ICR0 is changed to a low value when the
counter is running with none or a low prescaler value, there is a risk that the new ICR0 value written is
lower than the current value of TCNT0. As result, the counter will miss the compare match at the TOP
value. The counter will then have to count to the MAX value (0xFFFF) and wrap around starting at
0x0000 before the compare match can occur. The OCR0A Register however, is double buffered. This
feature allows the OCR0A I/O location to be written anytime. When the OCR0A I/O location is written the
value written will be put into the OCR0A Buffer Register. The OCR0A Compare Register will then be
updated with the value in the Buffer Register at the next timer clock cycle the TCNT0 matches TOP. The
update is done at the same timer clock cycle as the TCNT0 is cleared and the TOV0 Flag is set.
Using the ICR0 Register for defining TOP works well when using fixed TOP values. By using ICR0, the
OCR0A Register is free to be used for generating a PWM output on OC0A. However, if the base PWM
frequency is actively changed (by changing the TOP value), using the OCR0A as TOP is clearly a better
choice due to its double buffer feature.
In Fast PWM mode, the compare units allow generation of PWM waveforms on the OC0x pins. Writing
the COM0x[1:0] bits to 0x2 will produce an inverted PWM and a non-inverted PWM output can be
generated by writing the COM0x[1:0] to 0x3. The actual OC0x value will only be visible on the port pin if
the data direction for the port pin is set as output (DDR_OC0x). The PWM waveform is generated by
setting (or clearing) the OC0x Register at the compare match between OCR0x and TCNT0, and clearing
(or setting) the OC0x Register at the timer clock cycle the counter is cleared (changes from TOP to
BOTTOM).
The PWM frequency for the output can be calculated by the following equation:
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OCnxPWM =clk_I/O
1 + TOP
Note:
•The “n” in the register and bit names indicates the device number (n = 0 for Timer/Counter 0), and
the “x” indicates Output Compare unit (A/B).
•N represents the prescale divider (1, 8, 64, 256, or 1024).
The extreme values for the OCR0x registers represents special cases when generating a PWM waveform
output in the Fast PWM mode. If the OCR0x is set equal to BOTTOM (0x0000) the output will be a narrow
spike for each TOP+1 timer clock cycle. Setting the OCR0x equal to TOP will result in a constant high or
low output (depending on the polarity of the output which is controlled by COM0x[1:0]).
A frequency waveform output with 50% duty cycle can be achieved in Fast PWM mode by selecting
OC0A to toggle its logical level on each compare match (COM0A[1:0]=0x1). This applies only if OCR0A is
used to define the TOP value (WGM0[3:0]=0xF). The waveform generated will have a maximum
frequency of fOC0A = fclk_I/O/2 when OCR0A is set to zero (0x0000). This feature is similar to the OC0A
toggle in CTC mode, except the double buffer feature of the Output Compare unit is enabled in the Fast
PWM mode.
13.9.4. Phase Correct PWM Mode
The Phase Correct Pulse Width Modulation or Phase Correct PWM modes (WGM0[3:0]= 0x1, 0x2, 0x3,
0xA, and 0xB) provide a high resolution, phase correct PWM waveform generation option. The Phase
Correct PWM mode is, like the phase and frequency correct PWM mode, based on a dual-slope
operation. The counter counts repeatedly from BOTTOM (0x0000) to TOP and then from TOP to
BOTTOM. In non-inverting Compare Output mode, the Output Compare (OC0x) is cleared on the
compare match between TCNT0 and OCR0x while up-counting, and set on the compare match while
down-counting. In inverting Output Compare mode, the operation is inverted. The dual-slope operation
has lower maximum operation frequency than single slope operation. However, due to the symmetric
feature of the dual-slope PWM modes, these modes are preferred for motor control applications.
The PWM resolution for the Phase Correct PWM mode can be fixed to 8-, 9-, or 10-bit, or defined by
either ICR0 or OCR0A. The minimum resolution allowed is 2-bit (ICR0 or OCR0A set to 0x0003), and the
maximum resolution is 16-bit (ICR0 or OCR0A set to MAX). The PWM resolution in bits can be calculated
by using the following equation:
PCPWM =log TOP+1
log 2
In Phase Correct PWM mode the counter is incremented until the counter value matches either one of the
fixed values 0x00FF, 0x01FF, or 0x03FF (WGM0[3:0]= 0x1, 0x2, or 0x3), the value in ICR0
(WGM0[3:0]=0xA), or the value in OCR0A (WGM0[3:0]=0xB). The counter has then reached the TOP and
changes the count direction. The TCNT0 value will be equal to TOP for one timer clock cycle. The timing
diagram for the Phase Correct PWM mode is shown below, using OCR0A or ICR0 to define TOP. The
TCNT0 value is in the timing diagram shown as a histogram for illustrating the dual-slope operation. The
diagram includes non-inverted and inverted PWM outputs. The small horizontal lines on the TCNT0
slopes mark compare matches between OCR0x and TCNT0. The OC0x Interrupt Flag will be set when a
compare match occurs.
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Figure 13-10 Phase Correct PWM Mode, Timing Diagram
OCRnx/TOP Update and
OCnA Interrupt Flag Set
or ICFn Interrupt Flag Set
(Interrupt on TOP)
1 2 3 4
TOVn Interrupt Flag Set
(Interrupt on Bottom)
TCNTn
Period
OCnx
OCnx
(COMnx1:0 = 2)
(COMnx1:0 = 3)
The Timer/Counter Overflow Flag (TOV0) is set each time the counter reaches BOTTOM. When either
OCR0A or ICR0 is used for defining the TOP value, the OC0A or ICF0 Flag is set accordingly at the same
timer clock cycle as the OCR0x Registers are updated with the double buffer value (at TOP). The
Interrupt Flags can be used to generate an interrupt each time the counter reaches the TOP or BOTTOM
value.
When changing the TOP value the program must ensure that the new TOP value is higher or equal to the
value of all of the Compare Registers. If the TOP value is lower than any of the Compare Registers, a
compare match will never occur between the TCNT0 and the OCR0x. Note that when using fixed TOP
values, the unused bits are masked to zero when any of the OCR0x registers is written. As illustrated by
the third period in the timing diagram, changing the TOP actively while the Timer/Counter is running in the
phase correct mode can result in an unsymmetrical output. The reason for this can be found in the time of
update of the OCR0x Register. Since the OCR0x update occurs at TOP, the PWM period starts and ends
at TOP. This implies that the length of the falling slope is determined by the previous TOP value, while the
length of the rising slope is determined by the new TOP value. When these two values differ the two
slopes of the period will differ in length. The difference in length gives the unsymmetrical result on the
output.
It is recommended to use the phase and frequency correct mode instead of the phase correct mode when
changing the TOP value while the Timer/Counter is running. When using a static TOP value, there are
practically no differences between the two modes of operation.
In Phase Correct PWM mode, the compare units allow generation of PWM waveforms on the OC0x pins.
Writing COM0x[1:0] bits to 0x2 will produce a non-inverted PWM. An inverted PWM output can be
generated by writing the COM0x[1:0] to 0x3. The actual OC0x value will only be visible on the port pin if
the data direction for the port pin is set as output (DDR_OC0x). The PWM waveform is generated by
setting (or clearing) the OC0x Register at the compare match between OCR0x and TCNT0 when the
counter increments, and clearing (or setting) the OC0x Register at compare match between OCR0x and
TCNT0 when the counter decrements. The PWM frequency for the output when using Phase Correct
PWM can be calculated by the following equation:
OCnxPCPWM =clk_I/O
2 TOP
N represents the prescale divider (1, 8, 64, 256, or 1024).
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The extreme values for the OCR0x Register represent special cases when generating a PWM waveform
output in the Phase Correct PWM mode. If the OCR0x is set equal to BOTTOM the output will be
continuously low and if set equal to TOP the output will be continuously high for non-inverted PWM mode.
For inverted PWM the output will have the opposite logic values. If OCR0A is used to define the TOP
value (WGM0[3:0]=0xB) and COM0A[1:0]=0x1, the OC0A output will toggle with a 50% duty cycle.
13.9.5. Phase and Frequency Correct PWM Mode
The phase and frequency correct Pulse Width Modulation, or phase and frequency correct PWM mode
(WGM0[3:0] = 0x8 or 0x9) provides a high resolution phase and frequency correct PWM waveform
generation option. The phase and frequency correct PWM mode is, like the phase correct PWM mode,
based on a dual-slope operation. The counter counts repeatedly from BOTTOM (0x0000) to TOP and
then from TOP to BOTTOM. In non-inverting Compare Output mode, the Output Compare (OC0x) is
cleared on the compare match between TCNT0 and OCR0x while up-counting, and set on the compare
match while down-counting. In inverting Compare Output mode, the operation is inverted. The dual-slope
operation gives a lower maximum operation frequency compared to the single-slope operation. However,
due to the symmetric feature of the dual-slope PWM modes, these modes are preferred for motor control
applications.
The main difference between the phase correct, and the phase and frequency correct PWM mode is the
time the OCR0x Register is updated by the OCR0x Buffer Register, (see Figure 13-10 Phase Correct
PWM Mode, Timing Diagram on page 98 and the Timing Diagram below).
The PWM resolution for the phase and frequency correct PWM mode can be defined by either ICR0 or
OCR0A. The minimum resolution allowed is 2-bit (ICR0 or OCR0A set to 0x0003), and the maximum
resolution is 16-bit (ICR0 or OCR0A set to MAX). The PWM resolution in bits can be calculated using the
following equation:
PFCPWM =log TOP+1
log 2
In phase and frequency correct PWM mode the counter is incremented until the counter value matches
either the value in ICR0 (WGM0[3:0]=0x8), or the value in OCR0A (WGM0[3:0]=0x9). The counter has
then reached the TOP and changes the count direction. The TCNT0 value will be equal to TOP for one
timer clock cycle. The timing diagram for the phase correct and frequency correct PWM mode is shown
below. The figure shows phase and frequency correct PWM mode when OCR0A or ICR0 is used to
define TOP. The TCNT0 value is in the timing diagram shown as a histogram for illustrating the dual-slope
operation. The diagram includes non-inverted and inverted PWM outputs. The small horizontal line marks
on the TCNT0 slopes represent compare matches between OCR0x and TCNT0. The OC0x Interrupt Flag
will be set when a compare match occurs.
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Figure 13-11 Phase and Frequency Correct PWM Mode, Timing Diagram
OCRnx/TOP Updateand
TOVn Interrupt Flag Set
(Interrupt on Bottom)
OCnA Interrupt Flag Set
or ICFn Interrupt Flag Set
(Interrupt on TOP)
1 2 3 4
TCNTn
Period
OCnx
OCnx
(COMnx1:0 = 2)
(COMnx1:0 = 3)
Note: The “n” in the register and bit names indicates the device number (n = 0 for Timer/Counter 0), and
the “x” indicates Output Compare unit (A/B).
The Timer/Counter Overflow Flag (TOV0) is set at the same timer clock cycle as the OCR0x Registers
are updated with the double buffer value (at BOTTOM). When either OCR0A or ICR0 is used for defining
the TOP value, the OC0A or ICF0 Flag set when TCNT0 has reached TOP. The Interrupt Flags can then
be used to generate an interrupt each time the counter reaches the TOP or BOTTOM value.
When changing the TOP value the program must ensure that the new TOP value is higher or equal to the
value of all of the Compare Registers. If the TOP value is lower than any of the Compare Registers, a
compare match will never occur between the TCNT0 and the OCR0x.
As shown in the timing diagram above, the output generated is, in contrast to the phase correct mode,
symmetrical in all periods. Since the OCR0x Registers are updated at BOTTOM, the length of the rising
and the falling slopes will always be equal. This gives symmetrical output pulses and is therefore
frequency correct.
Using the ICR0 Register for defining TOP works well when using fixed TOP values. By using ICR0, the
OCR0A Register is free to be used for generating a PWM output on OC0A. However, if the base PWM
frequency is actively changed by changing the TOP value, using the OCR0A as TOP is clearly a better
choice due to its double buffer feature.
In phase and frequency correct PWM mode, the compare units allow generation of PWM waveforms on
the OC0x pins. Setting the COM0x[1:0] bits to 0x2 will produce a non-inverted PWM and an inverted
PWM output can be generated by setting the COM0x[1:0] to 0x3 (See description of TCCR0A.COM0x).
The actual OC0x value will only be visible on the port pin if the data direction for the port pin is set as
output (DDR_OC0x). The PWM waveform is generated by setting (or clearing) the OC0x Register at the
compare match between OCR0x and TCNT0 when the counter increments, and clearing (or setting) the
OC0x Register at compare match between OCR0x and TCNT0 when the counter decrements. The PWM
frequency for the output when using phase and frequency correct PWM can be calculated by the
following equation:
OCnxPFCPWM =clk_I/O
2 TOP
Note:
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•The “n” in the register and bit names indicates the device number (n = 0 for Timer/Counter 0), and
the “x” indicates Output Compare unit (A/B).
•N represents the prescale divider (1, 8, 64, 256, or 1024).
The extreme values for the OCR0x Register represents special cases when generating a PWM waveform
output in the phase correct PWM mode. If the OCR0x is set equal to BOTTOM the output will be
continuously low and if set equal to TOP the output will be set to high for non-inverted PWM mode. For
inverted PWM the output will have the opposite logic values. If OCR0A is used to define the TOP value
(WGM0[3:0]=0x9) and COM0A[1:0]=0x1, the OC0A output will toggle with a 50% duty cycle.
13.10. Timer/Counter Timing Diagrams
The Timer/Counter is a synchronous design and the timer clock (clkT0) is therefore shown as a clock
enable signal in the following figures. The figures include information on when Interrupt Flags are set, and
when the OCR0x Register is updated with the OCR0x buffer value (only for modes utilizing double
buffering). The first figure shows a timing diagram for the setting of OCF0x.
Figure 13-12 Timer/Counter Timing Diagram, Setting of OCF0x, no Prescaling
clkTn
(clkI/O/1)
OCFnx
clkI/O
OCRnx
TCNTn
OCRnx Value
OCRnx - 1 OCRnx OCRnx + 1 OCRnx + 2
Note: The “n” in the register and bit names indicates the device number (n = 0 for Timer/Counter 0), and
the “x” indicates Output Compare unit (A/B).
The next figure shows the same timing data, but with the prescaler enabled.
Figure 13-13 Timer/Counter Timing Diagram, Setting of OCF0x, with Prescaler (fclk_I/O/8)
OCFnx
OCRnx
TCNTn
OCRnx Value
OCRnx - 1 OCRnx OCRnx + 1 OCRnx + 2
clkI/O
clkTn
(clkI/O/8)
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Note: The “n” in the register and bit names indicates the device number (n = 0 for Timer/Counter 0), and
the “x” indicates Output Compare unit (A/B).
The next figure shows the count sequence close to TOP in various modes. When using phase and
frequency correct PWM mode the OCR0x Register is updated at BOTTOM. The timing diagrams will be
the same, but TOP should be replaced by BOTTOM, TOP-1 by BOTTOM+1 and so on. The same
renaming applies for modes that set the TOV0 Flag at BOTTOM.
Figure 13-14 Timer/Counter Timing Diagram, no Prescaling.
TOVn (FPWM)
and ICF n (if used
as TOP)
OCRnx
(Update at TOP)
TCNTn
(CTC and FPWM)
TCNTn
(PC and PFC PWM) TOP - 1 TOP TOP - 1 TOP - 2
Old OCRnx Value New OCRnx Value
TOP - 1 TOP BOTTOM BOTTOM + 1
clkTn
(clkI/O/1)
clkI/O
Note: The “n” in the register and bit names indicates the device number (n = 0 for Timer/Counter 0), and
the “x” indicates Output Compare unit (A/B).
The next figure shows the same timing data, but with the prescaler enabled.
Figure 13-15 Timer/Counter Timing Diagram, with Prescaler (fclk_I/O/8)
TOVn (FPWM)
and ICF n (if used
as TOP)
OCRnx
(Update at TOP)
TCNTn
(CTC and FPWM)
TCNTn
(PC and PFC PWM) TOP - 1 TOP TOP - 1 TOP - 2
Old OCRnx Value New OCRnx Value
TOP - 1 TOP BOTTOM BOTTOM + 1
clk
I/O
clk
Tn
(clk
I/O
/8)
Note: The “n” in the register and bit names indicates the device number (n = 0 for Timer/Counter 0), and
the “x” indicates Output Compare unit (A/B).
13.11. Register Description
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13.11.1. Timer/Counter0 Control Register A
Name: TCCR0A
Offset: 0x2E
Reset: 0x00
Property:
-
Bit 7 6 5 4 3 2 1 0
COM0A1 COM0A0 COM0B1 COM0B0 WGM01 WGM00
Access R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0
Bits 7:6 – COM0An: Compare Output Mode for Channel A [n = 1:0]
Bits 5:4 – COM0Bn: Compare Output Mode for Channel B [n = 1:0]
The COM0A[1:0] and COM0B[1:0] control the Output Compare pins (OC0A and OC0B respectively)
behavior. If one or both of the COM0A[1:0] bits are written to one, the OC0A output overrides the normal
port functionality of the I/O pin it is connected to. If one or both of the COM0B[1:0] bit are written to one,
the OC0B output overrides the normal port functionality of the I/O pin it is connected to. However, note
that the Data Direction Register (DDR) bit corresponding to the OC0A or OC0B pin must be set in order
to enable the output driver.
When the OC0A or OC0B is connected to the pin, the function of the COM0x[1:0] bits is dependent of the
WGM0[3:0] bits setting. The table below shows the COM0x[1:0] bit functionality when the WGM0[3:0] bits
are set to a Normal or a CTC mode (non-PWM).
Table 13-3 Compare Output Mode, non-PWM
COM0A1/COM0B1 COM0A0/COM0B0 Description
0 0 Normal port operation, OC0A/OC0B disconnected.
0 1 Toggle OC0A/OC0B on Compare Match.
1 0 Clear OC0A/OC0B on Compare Match (Set output to low
level).
1 1 Set OC0A/OC0B on Compare Match (Set output to high
level).
The table below shows the COM0x[1:0] bit functionality when the WGM0[3:0] bits are set to the fast PWM
mode.
Table 13-4 Compare Output Mode, Fast PWM
COM0A1/
COM0B1
COM0A0/
COM0B0
Description
0 0 Normal port operation, OC0A/OC0B disconnected.
0 1 WGM0[3:0]=0: Normal port operation, OC0A/OC0B
disconnected
WGM0[3:0]=1: Toggle OC0A on compare match, OC0B reserved
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COM0A1/
COM0B1
COM0A0/
COM0B0
Description
1(1) 0 Clear OC0A/OC0B on Compare Match, set OC0A/OC0B at
BOTTOM (non-inverting mode)
1(1) 1 Set OC0A/OC0B on Compare Match, clear OC0A/OC0B at
BOTTOM (inverting mode)
Note:
1. A special case occurs when OCR0A/OCR0B equals TOP and COM0A1/COM0B1 is set. In this
case the compare match is ignored, but the set or clear is done at BOTTOM. Refer to Fast PWM
Mode on page 95 for details.
The table below shows the COM0x[1:0] bit functionality when the WGM0[3:0] bits are set to the phase
correct or the phase and frequency correct, PWM mode.
Table 13-5 Compare Output Mode, Phase Correct and Phase and Frequency Correct PWM
COM0A1/
COM0B1
COM0A0/
COM0B0
Description
0 0 Normal port operation, OC0A/OC0B disconnected.
0 1 WGM0[3:0]=0: Normal port operation, OC0A/OC0B disconnected
WGM0[3:0]=1: Toggle OC0A on compare match, OC0B reserved
1(1) 0 Clear OC0A/OC0B on Compare Match when up-counting. Set
OC0A/OC0B on Compare Match when down-counting.
1(1) 1 Set OC0A/OC0B on Compare Match when up-counting. Clear
OC0A/OC0B on Compare Match when down-counting.
Note:
1. A special case occurs when OCR0A/OCR0B equals TOP and COM0A1/COM0B1 is set. Refer to
Phase Correct PWM Mode on page 97 for details.
Bits 1:0 – WGM0n: Waveform Generation Mode [n = 1:0]
Combined with the WGM0[3:2] bits found in the TCCR0B Register, these bits control the counting
sequence of the counter, the source for maximum (TOP) counter value, and what type of waveform
generation to be used. Modes of operation supported by the Timer/Counter unit are: Normal mode
(counter), Clear Timer on Compare match (CTC) mode, and three types of Pulse Width Modulation
(PWM) modes. (See Modes of Operation on page 93).
Table 13-6 Waveform Generation Mode Bit Description
Mode WGM0[3:0] Timer/Counter Mode of Operation TOP Update of OCR0x at TOV0 Flag Set on
0 0000 Normal 0xFFFF Immediate MAX
1 0001 PWM, Phase Correct, 8-bit 0x00FF TOP BOTTOM
2 0010 PWM, Phase Correct, 9-bit 0x01FF TOP BOTTOM
3 0011 PWM, Phase Correct, 10-bit 0x03FF TOP BOTTOM
4 0100 CTC (Clear Timer on Compare) OCR0A Immediate MAX
5 0101 Fast PWM, 8-bit 0x00FF TOP TOP
6 0110 Fast PWM, 9-bit 0x01FF TOP TOP
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Mode WGM0[3:0] Timer/Counter Mode of Operation TOP Update of OCR0x at TOV0 Flag Set on
7 0111 Fast PWM, 10-bit 0x03FF TOP TOP
8 1000 PWM, Phase and Frequency Correct ICR0 BOTTOM BOTTOM
9 1001 PWM, Phase and Frequency Correct OCR0A BOTTOM BOTTOM
10 1010 PWM, Phase Correct ICR0 TOP BOTTOM
11 1011 PWM, Phase Correct OCR0A TOP BOTTOM
12 1100 CTC (Clear Timer on Compare) ICR0 Immediate MAX
13 1101 Reserved - - -
14 1110 Fast PWM ICR0 TOP TOP
15 1111 Fast PWM OCR0A TOP TOP
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13.11.2. Timer/Counter0 Control Register B
Name: TCCR0B
Offset: 0x2D
Reset: 0x00
Property:
-
Bit 7 6 5 4 3 2 1 0
ICNC0 ICES0 WGM03 WGM02 CS0[2:0]
Access R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0
Bit 7 – ICNC0: Input Capture Noise Canceler
Setting this bit (to one) activates the Input Capture Noise Canceler. When the noise canceler is activated,
the input from the Input Capture pin (ICP0) is filtered. The filter function requires four successive equal
valued samples of the ICP0 pin for changing its output. The Input Capture is therefore delayed by four
Oscillator cycles when the noise canceler is enabled.
Bit 6 – ICES0: Input Capture Edge Select
This bit selects which edge on the Input Capture pin (ICP0) that is used to trigger a capture event. When
the ICES0 bit is written to zero, a falling (negative) edge is used as trigger, and when the ICES0 bit is
written to one, a rising (positive) edge will trigger the capture.
When a capture is triggered according to the ICES0 setting, the counter value is copied into the Input
Capture Register (ICR0). The event will also set the Input Capture Flag (ICF0), and this can be used to
cause an Input Capture Interrupt, if this interrupt is enabled.
When the ICR0 is used as TOP value (see description of the WGM0[3:0] bits located in the TCCR0A and
the TCCR0B Register), the ICP0 is disconnected and consequently the Input Capture function is
disabled.
Bit 4 – WGM03: Waveform Generation Mode
Refer to TCCR0A.
Bit 3 – WGM02: Waveform Generation Mode
Refer to TCCR0A.
Bits 2:0 – CS0[2:0]: Clock Select
The three Clock Select bits select the clock source to be used by the Timer/Counter. Refer to Figure
13-12 Timer/Counter Timing Diagram, Setting of OCF0x, no Prescaling on page 101 and Figure 13-13
Timer/Counter Timing Diagram, Setting of OCF0x, with Prescaler (fclk_I/O/8) on page 101.
Table 13-7 Clock Select Bit Description
CA0[2] CA0[1] CS0[0] Description
0 0 0 No clock source (Timer/Counter stopped).
0 0 1 clkI/O/1 (No prescaling)
0 1 0 clkI/O/8 (From prescaler)
0 1 1 clkI/O/64 (From prescaler)
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CA0[2] CA0[1] CS0[0] Description
1 0 0 clkI/O/256 (From prescaler)
1 0 1 clkI/O/1024 (From prescaler)
1 1 0 External clock source on T0 pin. Clock on falling edge.
1 1 1 External clock source on T0 pin. Clock on rising edge.
If external pin modes are used for the Timer/Counter 0, transitions on the T0 pin will clock the counter
even if the pin is configured as an output. This feature allows software control of the counting.
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13.11.3. Timer/Counter0 Control Register C
Name: TCCR0C
Offset: 0x2C
Reset: 0x00
Property:
-
Bit 7 6 5 4 3 2 1 0
FOC0A FOC0B
Access R/W R/W
Reset 0 0
Bit 7 – FOC0A: Force Output Compare for Channel A
Bit 6 – FOC0B: Force Output Compare for Channel B
The FOC0A/FOC0B bits are only active when the WGM0[3:0] bits specifies a non-PWM mode. When
writing a logical one to the FOC0A/FOC0B bit, an immediate compare match is forced on the Waveform
Generation unit. The OC0A/OC0B output is changed according to its COM0x[1:0] bits setting. Note that
the FOC0A/FOC0B bits are implemented as strobes. Therefore it is the value present in the COM0x[1:0]
bits that determine the effect of the forced compare.
A FOC0A/FOC0B strobe will not generate any interrupt nor will it clear the timer in Clear Timer on
Compare match (CTC) mode using OCR0A as TOP. The FOC0A/FOC0B bits are always read as zero.
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13.11.4. Timer/Counter0 High byte
Name: TCNT0H
Offset: 0x29
Reset: 0x00
Property:
-
Bit 7 6 5 4 3 2 1 0
(TCNT0[15:8]) TCNT0H[7:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bits 7:0 – (TCNT0[15:8]) TCNT0H[7:0]: Timer/Counter 0 High byte
TCNT0H and TCNT0L are combined into TCNT0. It also means TCNT0H[7:0] is TCNT0 [15:8]. Refer to
TCNT0L for more detail.
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13.11.5. Timer/Counter0 Low byte
Name: TCNT0L
Offset: 0x28
Reset: 0x00
Property:
-
Bit 7 6 5 4 3 2 1 0
(TCNT0[7:0]) TCNT0L[7:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bits 7:0 – (TCNT0[7:0]) TCNT0L[7:0]: Timer/Counter 0 Low byte
TCNT0H and TCNT0L are combined into TCNT0. It also means TCNT0L[7:0] is TCNT0[7:0].
The two Timer/Counter I/O locations (TCNT0H and TCNT0L, combined TCNT0) give direct access, both
for read and for write operations, to the Timer/Counter unit 16-bit counter. To ensure that both the high
and low bytes are read and written simultaneously when the CPU accesses these registers, the access is
performed using an 8-bit temporary High Byte Register (TEMP). This temporary register is shared by all
the other 16-bit registers. Refer to Accessing 16-bit Registers on page 83 for details.
Modifying the counter (TCNT0) while the counter is running introduces a risk of missing a compare match
between TCNT0 and one of the OCR0x Registers.
Writing to the TCNT0 Register blocks (removes) the compare match on the following timer clock for all
compare units.
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13.11.6. Output Compare Register 0 A High byte
Name: OCR0AH
Offset: 0x27
Reset: 0x00
Property:
-
Bit 7 6 5 4 3 2 1 0
(OCR0A[15:8]) OCR0AH[7:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bits 7:0 – (OCR0A[15:8]) OCR0AH[7:0]: Output Compare 0 A High byte
OCR0AH and OCR0AL are combined into OCR0A. It means OCR0AH[7:0] is OCR0A [15:8]. Refer to
OCR0AL.
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13.11.7. Output Compare Register 0 A Low byte
Name: OCR0AL
Offset: 0x26
Reset: 0x00
Property:
-
Bit 7 6 5 4 3 2 1 0
(OCR0A[7:0]) OCR0AL[7:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bits 7:0 – (OCR0A[7:0]) OCR0AL[7:0]: Output Compare 0 A Low byte
OCR0AH and OCR0AL are combined into OCR0A. It means OCR0AL[7:0] is OCR0A[7:0].
The Output Compare Registers contain a 16-bit value that is continuously compared with the counter
value (TCNT0). A match can be used to generate an Output Compare interrupt, or to generate a
waveform output on the OC0x pin.
The Output Compare Registers are 16-bit in size. To ensure that both the high and low bytes are written
simultaneously when the CPU writes to these registers, the access is performed using an 8-bit temporary
High Byte Register (TEMP). This temporary register is shared by all the other 16-bit registers. Refer to
Accessing 16-bit Registers on page 83 for details.
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13.11.8. Output Compare Register 0 B High byte
Name: OCR0BH
Offset: 0x25
Reset: 0x00
Property:
-
Bit 7 6 5 4 3 2 1 0
(OCR0B[15:8]) OCR0BH[7:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bits 7:0 – (OCR0B[15:8]) OCR0BH[7:0]: Output Compare 0 B High byte
OCR0BH and OCR0BL are combined into OCR0B. It means OCR0BH[7:0] is OCR0B[15:8]. Refer to
OCR0BL.
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13.11.9. Output Compare Register 0 B Low byte
Name: OCR0BL
Offset: 0x24
Reset: 0x00
Property:
-
Bit 7 6 5 4 3 2 1 0
(OCR0B[7:0]) OCR0BL[7:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bits 7:0 – (OCR0B[7:0]) OCR0BL[7:0]: Output Compare 0 B Low byte
OCR0BH and OCR0BL are combined into OCR0B. It means OCR0BL[7:0] is OCR0B[7:0].
The Output Compare Registers contain a 16-bit value that is continuously compared with the counter
value (TCNT0). A match can be used to generate an Output Compare interrupt, or to generate a
waveform output on the OC0x pin. The Output Compare Registers are 16-bit in size. To ensure that both
the high and low bytes are written simultaneously when the CPU writes to these registers, the access is
performed using an 8-bit temporary high byte register (TEMP). This temporary register is shared by all the
other 16-bit registers. See “Accessing 16-bit Registers”.
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13.11.10. Input Capture Register 0 High byte
Name: ICR0H
Offset: 0x23
Reset: 0x00
Property:
-
Bit 7 6 5 4 3 2 1 0
(ICR0[15:8]) ICR0H[7:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bits 7:0 – (ICR0[15:8]) ICR0H[7:0]: Input Capture 0 High byte
ICR0H and ICR0L are combined into ICR0. It means ICR0H[7:0] is ICR0[15:8]. Refer to ICR0L.
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13.11.11. Input Capture Register 0 Low byte
Name: ICR0L
Offset: 0x22
Reset: 0x00
Property:
-
Bit 7 6 5 4 3 2 1 0
(ICR0[7:0]) ICR0L[7:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bits 7:0 – (ICR0[7:0]) ICR0L[7:0]: Input Capture 0 Low byte
ICR0H and ICR0L are combined into ICR0. It means ICR0L[7:0] is ICR0[7:0].
The Input Capture is updated with the counter (TCNT0) value each time an event occurs on the ICP0 pin
(or optionally on the Analog Comparator output for Timer/Counter0). The Input Capture can be used for
defining the counter TOP value.
The Input Capture Register is 16-bit in size. To ensure that both the high and low bytes are read
simultaneously when the CPU accesses these registers, the access is performed using an 8-bit
temporary High Byte Register (TEMP). This temporary register is shared by all the other 16-bit registers.
Refer to Accessing 16-bit Registers on page 83 for details.
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13.11.12. Timer/Counter0 Interrupt Mask Register
Name: TIMSK0
Offset: 0x2B
Reset: 0x00
Property:
-
Bit 7 6 5 4 3 2 1 0
ICIE0 OCIE0B OCIE0A TOIE0
Access R/W R/W R/W R/W
Reset 0 0 0 0
Bit 5 – ICIE0: Timer/Counter0, Input Capture Interrupt Enable
When this bit is written to one, and the I-flag in the Status Register is set (interrupts globally enabled), the
Timer/Counter0 Input Capture interrupt is enabled. The corresponding Interrupt Vector is executed when
the ICF0 Flag, located in TIFR0, is set.
Bit 2 – OCIE0B: Timer/Counter0, Output Compare B Match Interrupt Enable
When this bit is written to one, and the I-flag in the Status Register is set (interrupts globally enabled), the
Timer/Counter 0 Output Compare B Match interrupt is enabled. The corresponding Interrupt Vector is
executed when the OCF0B Flag, located in TIFR0, is set.
Bit 1 – OCIE0A: Timer/Counter0, Output Compare A Match Interrupt Enable
When this bit is written to one, and the I-flag in the Status Register is set (interrupts globally enabled), the
Timer/Counter0 Output Compare A Match interrupt is enabled. The corresponding Interrupt Vector is
executed when the OCF0A Flag, located in TIFR0, is set.
Bit 0 – TOIE0: Timer/Counter0, Overflow Interrupt Enable
When this bit is written to one, and the I-flag in the Status Register is set (interrupts globally enabled), the
Timer/Counter0 Overflow interrupt is enabled. The corresponding Interrupt Vector is executed when the
TOV0 Flag, located in TIFR0, is set.
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13.11.13. Timer/Counter0 Interrupt Flag Register
Name: TIFR0
Offset: 0x2A
Reset: 0x00
Property:
Bit 7 6 5 4 3 2 1 0
ICF0 OCF0B OCF0A TOV0
Access R/W R/W R/W R/W
Reset 0 0 0 0
Bit 5 – ICF0: Timer/Counter0, Input Capture Flag
This flag is set when a capture event occurs on the ICP0 pin. When the Input Capture Register (ICR0) is
set by the WGM0[3:0] to be used as the TOP value, the ICF0 Flag is set when the counter reaches the
TOP value.
ICF0 is automatically cleared when the Input Capture Interrupt Vector is executed. Alternatively, ICF0 can
be cleared by writing a logic one to its bit location.
Bit 2 – OCF0B: Timer/Counter0, Output Compare B Match Flag
This flag is set in the timer clock cycle after the counter (TCNT0) value matches the Output Compare
Register B (OCR0B).
Note that a Forced Output Compare (FOC0B) strobe will not set the OCF0B Flag.
OCF0B is automatically cleared when the Output Compare Match B Interrupt Vector is executed.
Alternatively, OCF0B can be cleared by writing a logic one to its bit location.
Bit 1 – OCF0A: Timer/Counter0, Output Compare A Match Flag
This flag is set in the timer clock cycle after the counter (TCNT0) value matches the Output Compare
Register A (OCR0A).
Note that a Forced Output Compare (FOC0A) strobe will not set the OCF0A Flag.
OCF0A is automatically cleared when the Output Compare Match A Interrupt Vector is executed.
Alternatively, OCF0A can be cleared by writing a logic one to its bit location.
Bit 0 – TOV0: Timer/Counter0, Overflow Flag
The setting of this flag is dependent of the WGM0[3:0] bits setting. In Normal and CTC modes, the TOV0
Flag is set when the timer overflows. Refer to Table 13-6 Waveform Generation Mode Bit Description on
page 104 for the TOV0 Flag behavior when using another WGM0[3:0] bit setting.
TOV0 is automatically cleared when the Timer/Counter0 Overflow Interrupt Vector is executed.
Alternatively, TOV0 can be cleared by writing a logic one to its bit location.
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13.11.14. General Timer/Counter Control Register
Name: GTCCR
Offset: 0x2F
Reset: 0x00
Property:
Bit 7 6 5 4 3 2 1 0
TSM PSR
Access R/W R/W
Reset 0 0
Bit 7 – TSM: Timer/Counter Synchronization Mode
Writing the TSM bit to one activates the Timer/Counter Synchronization mode. In this mode, the value
that is written to the PSR bit is kept, hence keeping the Prescaler Reset signal asserted. This ensures
that the Timer/Counter is halted and can be configured without the risk of advancing during configuration.
When the TSM bit is written to zero, the PSR bit is cleared by hardware, and the Timer/Counter start
counting.
Bit 0 – PSR: Prescaler 0 Reset Timer/Counter 0
When this bit is one, the Timer/Counter0 prescaler will be Reset. This bit is normally cleared immediately
by hardware, except if the TSM bit is set.
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14. Analog Comparator
14.1. Overview
The Analog Comparator compares the input values on the positive pin AIN0 and negative pin AIN1. When
the voltage on the positive pin AIN0 is higher than the voltage on the negative pin AIN1, the Analog
Comparator output, ACO (on Port E[0]), is set. The comparator’s output can be set to trigger the Timer/
Counter1 Input Capture function. In addition, the comparator can trigger a separate interrupt, exclusive to
the Analog Comparator. The user can select Interrupt triggering on comparator output rise, fall or toggle.
A block diagram of the comparator and its surrounding logic is shown below.
The Power Reduction ADC bit in the Power Reduction Register (PRR.PRADC) must be written to '0' in
order to be able to use the ADC input MUX.
Figure 14-1 Analog Comparator Block Diagram
Note: Refer to the Pin Configuration and the I/O Ports description for Analog Comparator pin placement.
Related Links
Pin Configurations on page 7
14.2. Register Description
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14.2.1. Analog Comparator Control and Status Register
Name: ACSR
Offset: 0x1F
Reset: 0
Property:
When addressing I/O Registers as data space the offset address is 0x50
Bit 7 6 5 4 3 2 1 0
ACD ACO ACI ACIE ACIC ACIS1 ACIS0
Access R/W R R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0
Bit 7 – ACD: Analog Comparator Disable
When this bit is written logic one, the power to the Analog Comparator is switched off. This bit can be set
at any time to turn off the Analog Comparator. This will reduce power consumption in Active and Idle
mode. When changing the ACD bit, the Analog Comparator Interrupt must be disabled by clearing the
ACIE bit in ACSR. Otherwise an interrupt can occur when the bit is changed.
Bit 5 – ACO: Analog Comparator Output
The output of the Analog Comparator is synchronized and then directly connected to ACO. The
synchronization introduces a delay of 1 - 2 clock cycles.
Bit 4 – ACI: Analog Comparator Interrupt Flag
This bit is set by hardware when a comparator output event triggers the interrupt mode defined by ACIS1
and ACIS0. The Analog Comparator interrupt routine is executed if the ACIE bit is set and the I-bit in
SREG is set. ACI is cleared by hardware when executing the corresponding interrupt handling vector.
Alternatively, ACI is cleared by writing a logic one to the flag.
Bit 3 – ACIE: Analog Comparator Interrupt Enable
When the ACIE bit is written logic one and the I-bit in the Status Register is set, the Analog Comparator
interrupt is activated. When written logic zero, the interrupt is disabled.
Bit 2 – ACIC: Analog Comparator Input Capture Enable
When written logic one, this bit enables the input capture function in Timer/Counter0 to be triggered by
the Analog Comparator. The comparator output is in this case directly connected to the input capture
front-end logic, making the comparator utilize the noise canceler and edge select features of the Timer/
Counter0 Input Capture interrupt. When written logic zero, no connection between the Analog
Comparator and the input capture function exists. To make the comparator trigger the Timer/Counter0
Input Capture interrupt, the ICIE1 bit in the Timer Interrupt Mask Register (TIMSK0) must be set.
Bits 1:0 – ACISn: Analog Comparator Interrupt Mode Select [n = 1:0]
These bits determine which comparator events that trigger the Analog Comparator interrupt.
Table 14-1 ACIS[1:0] Settings
ACIS1 ACIS0 Interrupt Mode
0 0 Comparator Interrupt on Output Toggle.
0 1 Reserved
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ACIS1 ACIS0 Interrupt Mode
1 0 Comparator Interrupt on Falling Output Edge.
1 1 Comparator Interrupt on Rising Output Edge.
When changing the ACIS1/ACIS0 bits, the Analog Comparator Interrupt must be disabled by clearing its
Interrupt Enable bit in the ACSR Register. Otherwise an interrupt can occur when the bits are changed.
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14.2.2. Digital Input Disable Register 0
When the respective bits are written to logic one, the digital input buffer on the corresponding ADC pin is
disabled. The corresponding PIN Register bit will always read as zero when this bit is set. When an
analog signal is applied to the ADC[3:0] pin and the digital input from this pin is not needed, this bit should
be written logic one to reduce power consumption in the digital input buffer.
Name: DIDR0
Offset: 0x17
Reset: 0x00
Property:
-
Bit 7 6 5 4 3 2 1 0
ADC3D ADC2D ADC1D ADC0D
Access R/W R/W R/W R/W
Reset 0 0 0 0
Bit 3 – ADC3D: ADC3 Digital Input Disable
Not apply for AC.
Bit 2 – ADC2D: ADC2 Digital Input Disable
Not apply for AC.
Bit 1 – ADC1D: ADC1 Digital Input Disable
Bit 0 – ADC0D: ADC0 Digital Input Disable
For AC: When this bit is set, the digital input buffer on pin AIN1 (ADC1) / AIN0 (ADC0) is disabled and the
corresponding PIN register bit will read as zero. When used as an analog input but not required as a
digital input the power consumption in the digital input buffer can be reduced by writing this bit to logic
one.
For ADC: When this bit is written logic one, the digital input buffer on the corresponding ADC pin is
disabled. The corresponding PIN register bit will always read as zero when this bit is set. When an analog
signal is applied to the ADC[3:0] pin and the digital input from this pin is not needed, this bit should be
written logic one to reduce power consumption in the digital input buffer.
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15. ADC - Analog to Digital Converter
15.1. Features
•8-bit Resolution
•0.5 LSB Integral Non-Linearity
•±1 LSB Absolute Accuracy
•65 μs Conversion Time
•15 kSPS at Full Resolution
•Four Multiplexed Single Ended Input Channels
•Input Voltage Range: 0 - VCC
•Supply Voltage Range: 2.5 V – 5.5 V
•Free Running or Single Conversion Mode
•ADC Start Conversion by Auto Triggering on Interrupt Sources
•Interrupt on ADC Conversion Complete
•Sleep Mode Noise Canceler
15.2. Overview
ATtiny5/10 feature an 8-bit, successive approximation ADC. The ADC is connected to a 4-channel analog
multiplexer which allows four single-ended voltage inputs constructed from the pins of port B. The single-
ended voltage inputs refer to 0V (GND).
The ADC contains a Sample and Hold circuit which ensures that the input voltage to the ADC is held at a
constant level during conversion.
Internal reference voltage of VCC is provided on-chip.
The ADC is not available in ATtiny4/9.
The Power Reduction ADC bit in the Power Reduction Register (PRR.PRADC) must be written to '0' in
order to be enable the ADC.
The ADC converts an analog input voltage to an 8-bit digital value through successive approximation. The
minimum value represents GND and the maximum value represents the voltage on the voltage on VCC.
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Figure 15-1 Analog to Digital Converter Block Schematic Operation
ADMUX
DECODER
8-BIT DATA BUS
MUX1
MUX0
ADCSRA ADCL
ADP S0
ADEN
ADP S1
ADP S2
ADATE
ADIF
ADS C
TRIGGER
SELECT
VREF
ADTS 2:0
START
PRESCALER
ADC7:0
CONVERSION LOGIC
8-BIT DAC
ADCSRB
-
+
ADC3
ADC2
ADC1
ADC0
VCC
INPUT
MUX
INTERRUP T FLAGS
ADIE
ADC IRQ
SAMPLE & HOLD
COMPARATOR
CHANNEL
The analog input channel is selected by writing to the MUX bits in the ADC Multiplexer Selection register
(ADMUX.MUX). Any of the ADC input pins can be selected as single ended inputs to the ADC. The ADC
is enabled by writing a '1' to the ADC Enable bit in the ADC Control and Status Register A
(ADCSRA.ADEN). Voltage reference and input channel selections will not take effect until ADEN is set.
The ADC does not consume power when ADEN is cleared, so it is recommended to switch off the ADC
before entering power saving sleep modes.
Related Links
PRR on page 45
ADMUX on page 134
ADCL on page 138
15.3. Starting a Conversion
A single conversion is started by writing a '0' to the Power Reduction ADC bit in the Power Reduction
Register (PRR.PRADC), and writing a '1' to the ADC Start Conversion bit in the ADC Control and Status
Register A (ADCSRA.ADSC). ADCS will stay high as long as the conversion is in progress, and will be
cleared by hardware when the conversion is completed. If a different data channel is selected while a
conversion is in progress, the ADC will finish the current conversion before performing the channel
change.
Alternatively, a conversion can be triggered automatically by various sources. Auto Triggering is enabled
by setting the ADC Auto Trigger Enable bit (ADCSRA.ADATE). The trigger source is selected by setting
the ADC Trigger Select bits in the ADC Control and Status Register B (ADCSRB.ADTS). See the
description of the ADCSRB.ADTS for a list of available trigger sources.
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When a positive edge occurs on the selected trigger signal, the ADC prescaler is reset and a conversion
is started. This provides a method of starting conversions at fixed intervals. If the trigger signal still is set
when the conversion completes, a new conversion will not be started. If another positive edge occurs on
the trigger signal during conversion, the edge will be ignored. Note that an interrupt flag will be set even if
the specific interrupt is disabled or the Global Interrupt Enable bit in the AVR Status REgister (SREG.I) is
cleared. A conversion can thus be triggered without causing an interrupt. However, the Interrupt Flag
must be cleared in order to trigger a new conversion at the next interrupt event.
Figure 15-2 ADC Auto Trigger Logic
ADSC
ADIF
SOURCE 1
SOURCE n
ADTS[2:0]
CONVERSION
LOGIC
PRESCALER
START CLKADC
.
.
.
.EDGE
DETECTOR
ADATE
Using the ADC Interrupt Flag as a trigger source makes the ADC start a new conversion as soon as the
ongoing conversion has finished. The ADC then operates in Free Running mode, constantly sampling
and updating the ADC Data Register. The first conversion must be started by writing a '1' to
ADCSRA.ADSC. In this mode the ADC will perform successive conversions independently of whether the
ADC Interrupt Flag (ADIF) is cleared or not.
If Auto Triggering is enabled, single conversions can be started by writing ADCSRA.ADSC to '1'. ADSC
can also be used to determine if a conversion is in progress. The ADSC bit will be read as '1' during a
conversion, independently of how the conversion was started.
Related Links
PRR on page 45
15.4. Prescaling and Conversion Timing
By default, the successive approximation circuitry requires an input clock frequency between 50 kHz and
200 kHz to get maximum resolution.
The ADC module contains a prescaler, which generates an acceptable ADC clock frequency from any
CPU frequency above 100 kHz. The prescaling is selected by the ADC Prescaler Select bits in the ADC
Control and Status Register A (ADCSRA.ADPS). The prescaler starts counting from the moment the ADC
is switched on by writing the ADC Enable bit ADCSRA.ADEN to '1'. The prescaler keeps running for as
long as ADEN=1, and is continuously reset when ADEN=0.
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Figure 15-3 ADC Prescaler
7-BIT ADC PRESCALER
ADC CLOCK SOURCE
CK
ADPS0
ADPS1
ADPS2
CK/128
CK/2
CK/4
CK/8
CK/16
CK/32
CK/64
Reset
ADEN
START
When initiating a single ended conversion by writing a '1' to the ADC Start Conversion bit
(ADCSRA.ADSC), the conversion starts at the following rising edge of the ADC clock cycle.
A normal conversion takes 13 ADC clock cycles. The first conversion after the ADC is switched on (i.e.,
ADCSRA.ADEN is written to '1') takes 25 ADC clock cycles in order to initialize the analog circuitry, as the
figure below.
Figure 15-4 ADC Timing Diagram, First Conversion (Single Conversion Mode)
Convers ion Re sult
ADC Clock
ADS C
Sa mple & Hold
ADIF
ADCL
Cycle Numbe r
ADEN
1 2 12 13 14 15 16 17 18 19 20 21 22 23 24 25 1 2
Firs t Convers ion Next
Convers ion
3
MUX
Upda te MUX
Upda te
Convers ion
Complete
The actual sample-and-hold takes place 3 ADC clock cycles after the start of a normal conversion and 16
ADC clock cycles after the start of an first conversion. When a conversion is complete, the result is written
to the ADC Data Registers (ADCL), and the ADC Interrupt Flag (ADCSRA.ADIF) is set. In Single
Conversion mode, ADCSRA.ADSC is cleared simultaneously. The software may then set
ADCSRA.ADSC again, and a new conversion will be initiated on the first rising ADC clock edge.
Figure 15-5 ADC Timing Diagram, Single Conversion
12 3 4 5 6 7 8 9 10 11 12 13
Conve rsion Re sult
ADC Clock
ADS C
ADIF
ADCL
Cycle Numbe r 1 2
One Convers ion Next Conve rsion
3
Sample & Hold
MUX
Update Conversion
Complete MUX
Update
When Auto Triggering is used, the prescaler is reset when the trigger event occurs, as the next figure.
This assures a fixed delay from the trigger event to the start of conversion. In this mode, the sample-and-
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hold takes place 2 ADC clock cycles after the rising edge on the trigger source signal. Three additional
CPU clock cycles are used for synchronization logic.
Figure 15-6 ADC Timing Diagram, Auto Triggered Conversion
1 2 3 4 5 6 7 8 910 11 12 13
Conve rsion Result
A
DC Clock
T
rigge r
S
ource
A
DIF
A
DCL
C
ycle Number 1 2
One Conve rsion Next Convers ion
Conve rsion
Complete
Pres ca ler
Rese t
A
DATE
Pres ca ler
Rese t
Sample &
Hold
MUX
Update
In Free Running mode, a new conversion will be started immediately after the conversion completes,
while ADCRSA.ADSC remains high. See also the ADC Conversion Time table below.
Figure 15-7 ADC Timing Diagram, Free Running Conversion
11 12 13
Conve rs ion Res ult
ADC Clock
ADSC
ADIF
ADCL
Cycle Number 1 2
One Convers ion Next Convers ion
3 4
Conve rs ion complete Sa mple & Hold
MUX upda te
Table 15-1 ADC Conversion Time
Condition Sample & Hold
(Cycles from Start of Conversion)
Conversion Time
(Cycles)
First conversion 16.5 25
Normal conversions, single ended 3.5 13
Auto Triggered conversions 4 13.5
15.5. Changing Channel or Reference Selection
The Analog Channel Selection bits (MUX) in the ADC Multiplexer Selection Register (ADCMUX.MUX) are
single buffered through a temporary register to which the CPU has random access. This ensures that the
channels and reference selection only takes place at a safe point during the conversion. The channel
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selection is continuously updated until a conversion is started. Once the conversion starts, the channel
selection is locked to ensure a sufficient sampling time for the ADC. Continuous updating resumes in the
last ADC clock cycle before the conversion completes (indicated by ADCSRA.ADIF set). Note that the
conversion starts on the following rising ADC clock edge after ADSC is written. The user is thus advised
not to write new channel or reference selection values to ADMUX until one ADC clock cycle after the ADC
Start Conversion bit (ADCRSA.ADSC) was written.
If Auto Triggering is used, the exact time of the triggering event can be indeterministic. Special care must
be taken when updating the ADMUX Register, in order to control which conversion will be affected by the
new settings.
If both the ADC Auto Trigger Enable (ADCRSA.ADATE) and ADC Enable bits (ADCRSA.ADEN) are
written to '1', an interrupt event can occur at any time. If the ADMUX Register is changed in this period,
the user cannot tell if the next conversion is based on the old or the new settings. ADMUX can be safely
updated in the following ways:
1. When ADATE or ADEN is cleared.
1.1. During conversion, minimum one ADC clock cycle after the trigger event.
1.2. After a conversion, before the Interrupt Flag used as trigger source is cleared.
When updating ADMUX in one of these conditions, the new settings will affect the next ADC conversion.
15.6. ADC Input Channels
When changing channel selections, the user should observe the following guidelines to ensure that the
correct channel is selected:
•In Single Conversion mode, always select the channel before starting the conversion. The channel
selection may be changed one ADC clock cycle after writing one to ADSC. However, the simplest
method is to wait for the conversion to complete before changing the channel selection.
•In Free Running mode, always select the channel before starting the first conversion. The channel
selection may be changed one ADC clock cycle after writing one to ADSC. However, the simplest
method is to wait for the first conversion to complete, and then change the channel selection. Since
the next conversion has already started automatically, the next result will reflect the previous
channel selection. Subsequent conversions will reflect the new channel selection. The user is
advised not to write new channel or reference selection values during Free Running mode.
15.7. ADC Voltage Reference
The reference voltage for the ADC (VREF) indicates the conversion range, which in this case is limited to
0V (VGND) and VREF = Vcc. Single ended channels that exceed VREF will result in codes close to 0xFF.
15.8. ADC Noise Canceler
The ADC features a noise canceler that enables conversion during sleep mode to reduce noise induced
from the CPU core and other I/O peripherals. The noise canceler can be used with ADC Noise Reduction
and Idle mode. To make use of this feature, the following procedure should be used:
1. Make sure that the ADC is enabled and is not busy converting. Single Conversion mode must be
selected and the ADC conversion complete interrupt must be enabled.
2. Enter ADC Noise Reduction mode (or Idle mode). The ADC will start a conversion once the CPU
has been halted.
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3. If no other interrupts occur before the ADC conversion completes, the ADC interrupt will wake up
the CPU and execute the ADC Conversion Complete interrupt routine. If another interrupt wakes up
the CPU before the ADC conversion is complete, that interrupt will be executed, and an ADC
Conversion Complete interrupt request will be generated when the ADC conversion completes. The
CPU will remain in active mode until a new sleep command is executed.
Note: The ADC will not be automatically turned off when entering other sleep modes than Idle mode and
ADC Noise Reduction mode. The user is advised to write zero to ADCRSA.ADEN before entering such
sleep modes to avoid excessive power consumption.
15.9. Analog Input Circuitry
The analog input circuitry for single ended channels is illustrated below. An analog source applied to
ADCn is subjected to the pin capacitance and input leakage of that pin, regardless of whether that
channel is selected as input for the ADC. When the channel is selected, the source must drive the S/H
capacitor through the series resistance (combined resistance in the input path).
The ADC is optimized for analog signals with an output impedance of approximately 10 kΩ or less. If such
a source is used, the sampling time will be negligible. If a source with higher impedance is used, the
sampling time will depend on how long time the source needs to charge the S/H capacitor, with can vary
widely. The user is recommended to only use low impedance sources with slowly varying signals, since
this minimizes the required charge transfer to the S/H capacitor.
Signal components higher than the Nyquist frequency (fADC/2) should not be present for either kind of
channels, to avoid distortion from unpredictable signal convolution. The user is advised to remove high
frequency components with a low-pass filter before applying the signals as inputs to the ADC.
Figure 15-8 Analog Input Circuitry
ADCn
IIH
1..100k Ω
CS/H
= 14pF
IIL
VCC/2
15.10. Analog Noise Canceling Techniques
Digital circuitry inside and outside the device generates EMI which might affect the accuracy of analog
measurements. If conversion accuracy is critical, the noise level can be reduced by applying the following
techniques:
•Keep analog signal paths as short as possible.
•Make sure analog tracks run over the analog ground plane
•Keep analog tracks well away from high-speed switching digital tracks.
•If any port pin is used as a digital output, it mustn’t switch while a conversion is in progress.
•Place bypass capacitors as close to VCC and GND pins as possible.
When high ADC accuracy is required it is recommended to use ADC Noise Reduction Mode. A good
system design with properly placed, external bypass capacitors does reduce the need for using ADC
Noise Reduction Mode.
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15.11. ADC Accuracy Definitions
An n-bit single-ended ADC converts a voltage linearly between GND and VREF in 2n steps (LSBs). The
lowest code is read as 0, and the highest code is read as 2n-1.
Several parameters describe the deviation from the ideal behavior:
•Offset: The deviation of the first transition (0x00 to 0x01) compared to the ideal transition (at 0.5
LSB). Ideal value: 0 LSB.
Figure 15-9 Offset Error
Output Code
V
REF Input Voltage
Ideal ADC
Actual ADC
Offset
Error
•Gain error: After adjusting for offset, the gain error is found as the deviation of the last transition
(0xFE to 0xFF) compared to the ideal transition (at 1.5 LSB below maximum). Ideal value: 0 LSB.
Figure 15-10 Gain Error
Output Code
V
REF Input Voltage
Ideal ADC
Actual ADC
Gain
Error
•Integral Non-linearity (INL): After adjusting for offset and gain error, the INL is the maximum
deviation of an actual transition compared to an ideal transition for any code. Ideal value: 0 LSB.
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Figure 15-11 Integral Non-linearity (INL)
Output Code
V
REF Input Voltage
Ideal ADC
Actual ADC
INL
•Differential Non-linearity (DNL): The maximum deviation of the actual code width (the interval
between two adjacent transitions) from the ideal code width (1 LSB). Ideal value: 0 LSB.
Figure 15-12 Differential Non-linearity (DNL)
Output Code
0x3FF
0x000
0V
REF Input Voltage
DNL
1 LSB
•Quantization Error: Due to the quantization of the input voltage into a finite number of codes, a
range of input voltages (1 LSB wide) will code to the same value. Always ±0.5 LSB.
•Absolute accuracy: The maximum deviation of an actual (unadjusted) transition compared to an
ideal transition for any code. This is the compound effect of offset, gain error, differential error, non-
linearity, and quantization error. Ideal value: ±0.5 LSB.
15.12. ADC Conversion Result
After the conversion is complete (ADCSRA.ADIF is set), the conversion result can be found in the ADC
Data Registers (ADCL).
For single ended conversion, the result is
ADC=IN 256
where VIN is the voltage on the selected input pin, and VCC the selected voltage reference (see also
descriptions of ADMUX.MUX). 0x00 represents analog ground, and 0xFF represents the selected
reference voltage minus one LSB.
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15.13. Register Description
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15.13.1. ADC Multiplexer Selection Register
Name: ADMUX
Offset: 0x1B
Reset: 0x00
Property:
-
Bit 7 6 5 4 3 2 1 0
MUX1 MUX0
Access R/W R/W
Reset 0 0
Bits 1:0 – MUXn: Analog Channel Selection [n = 1:0]
The value of these bits selects which analog inputs are connected to the ADC. If these bits are changed
during a conversion, the change will not go in effect until this conversion is complete (ADCSRA.ADIF is
set).
Table 15-2 Input Channel Selection
MUX[1:0] Single Ended Input Pin
00 ADC0 PB0
01 ADC1 PB1
10 ADC2 PB2
11 ADC3 PB3
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15.13.2. ADC Control and Status Register A
Name: ADCSRA
Offset: 0x1D
Reset: 0x00
Property:
-
Bit 7 6 5 4 3 2 1 0
ADEN ADSC ADATE ADIF ADIE ADPS2 ADPS1 ADPS0
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 7 – ADEN: ADC Enable
Writing this bit to one enables the ADC. By writing it to zero, the ADC is turned off. Turning the ADC off
while a conversion is in progress, will terminate this conversion.
Bit 6 – ADSC: ADC Start Conversion
In Single Conversion mode, write this bit to one to start each conversion. In Free Running mode, write
this bit to one to start the first conversion. The first conversion after ADSC has been written after the ADC
has been enabled, or if ADSC is written at the same time as the ADC is enabled, will take 25 ADC clock
cycles instead of the normal 13. This first conversion performs initialization of the ADC.
ADSC will read as one as long as a conversion is in progress. When the conversion is complete, it returns
to zero. Writing zero to this bit has no effect.
Bit 5 – ADATE: ADC Auto Trigger Enable
When this bit is written to one, Auto Triggering of the ADC is enabled. The ADC will start a conversion on
a positive edge of the selected trigger signal. The trigger source is selected by setting the ADC Trigger
Select bits, ADTS in ADCSRB.
Bit 4 – ADIF: ADC Interrupt Flag
This bit is set when an ADC conversion completes and the Data Registers are updated. The ADC
Conversion Complete Interrupt is executed if the ADIE bit and the I-bit in SREG are set. ADIF is cleared
by hardware when executing the corresponding interrupt handling vector. Alternatively, ADIF is cleared by
writing a logical one to the flag. Beware that if doing a Read-Modify-Write on ADCSRA, a pending
interrupt can be disabled. This also applies if the SBI and CBI instructions are used.
Bit 3 – ADIE: ADC Interrupt Enable
When this bit is written to one and the I-bit in SREG is set, the ADC Conversion Complete Interrupt is
activated.
Bits 2:0 – ADPSn: ADC Prescaler Select [n = 2:0]
These bits determine the division factor between the system clock frequency and the input clock to the
ADC.
Table 15-3 Input Channel Selection
ADPS[2:0] Division Factor
000 2
001 2
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ADPS[2:0] Division Factor
010 4
011 8
100 16
101 32
110 64
111 128
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15.13.3. ADC Control and Status Register B
Name: ADCSRB
Offset: 0x1C
Reset: 0x00
Property:
-
Bit 7 6 5 4 3 2 1 0
ADTS2 ADTS1 ADTS0
Access R/W R/W R/W
Reset 0 0 0
Bits 2:0 – ADTSn: ADC Auto Trigger Source [n = 2:0]
If ADATE in ADCSRA is written to one, the value of these bits selects which source will trigger an ADC
conversion. If ADATE is cleared, the ADTS[2:0] settings will have no effect. A conversion will be triggered
by the rising edge of the selected Interrupt Flag. Note that switching from a trigger source that is cleared
to a trigger source that is set, will generate a positive edge on the trigger signal. If ADEN in ADCSRA is
set, this will start a conversion. Switching to Free Running mode (ADTS[2:0]=0) will not cause a trigger
event, even if the ADC Interrupt Flag is set.
Table 15-4 ADC Auto Trigger Source Selection
ADTS[2:0] Trigger Source
000 Free Running mode
001 Analog Comparator
010 External Interrupt Request 0
011 Timer/Counter 0 Compare Match A
100 Timer/Counter 0 Overflow
101 Timer/Counter 0 Compare Match B
110 Pin Change Interrupt 0 Request
111 Timer/Counter 0 Capture Event
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15.13.4. ADC Conversion Result Low Byte
When an ADC conversion is complete, the result is found in the ADC register.
Name: ADCL
Offset: 0x19
Reset: 0x00
Property:
Bit 7 6 5 4 3 2 1 0
ADC7 ADC6 ADC5 ADC4 ADC3 ADC2 ADC1 ADC0
Access R R R R R R R R
Reset 0 0 0 0 0 0 0 0
Bits 7:0 – ADCn: ADC Conversion Result [7:0]
These bits represent the result from the conversion.
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15.13.5. Digital Input Disable Register 0
When the respective bits are written to logic one, the digital input buffer on the corresponding ADC pin is
disabled. The corresponding PIN Register bit will always read as zero when this bit is set. When an
analog signal is applied to the ADC[3:0] pin and the digital input from this pin is not needed, this bit should
be written logic one to reduce power consumption in the digital input buffer.
Name: DIDR0
Offset: 0x17
Reset: 0x00
Property:
-
Bit 7 6 5 4 3 2 1 0
ADC3D ADC2D ADC1D ADC0D
Access R/W R/W R/W R/W
Reset 0 0 0 0
Bit 3 – ADC3D: ADC3 Digital Input Disable
Not apply for AC.
Bit 2 – ADC2D: ADC2 Digital Input Disable
Not apply for AC.
Bit 1 – ADC1D: ADC1 Digital Input Disable
Bit 0 – ADC0D: ADC0 Digital Input Disable
For AC: When this bit is set, the digital input buffer on pin AIN1 (ADC1) / AIN0 (ADC0) is disabled and the
corresponding PIN register bit will read as zero. When used as an analog input but not required as a
digital input the power consumption in the digital input buffer can be reduced by writing this bit to logic
one.
For ADC: When this bit is written logic one, the digital input buffer on the corresponding ADC pin is
disabled. The corresponding PIN register bit will always read as zero when this bit is set. When an analog
signal is applied to the ADC[3:0] pin and the digital input from this pin is not needed, this bit should be
written logic one to reduce power consumption in the digital input buffer.
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16. Programming interface
16.1. Features
•Physical Layer:
–Synchronous Data Transfer
–Bi-directional, Half-duplex Receiver And Transmitter
–Fixed Frame Format With One Start Bit, 8 Data Bits, One Parity Bit And 2 Stop Bits
–Parity Error Detection, Frame Error Detection And Break Character Detection
–Parity Generation And Collision Detection – Automatic Guard Time Insertion Between Data
Reception And Transmission
•Access Layer:
–Communication Based On Messages
–Automatic Exception Handling Mechanism
–Compact Instruction Set
–NVM Programming Access Control
–Tiny Programming Interface Control And Status Space Access Control
–Data Space Access Control
16.2. Overview
The Tiny Programming Interface (TPI) supports external programming of all Non-Volatile Memories
(NVM). Memory programming is done via the NVM Controller, by executing NVM controller commands as
described in Memory Programming.
The Tiny Programming Interface (TPI) provides access to the programming facilities. The interface
consists of two layers: the access layer and the physical layer.
Figure 16-1 The Tiny Programming Interface and Related Internal Interfaces
ACCESS
LAYER
PHYSICAL
LAYER
NVM
CONTROLLER
NON-VOLATILE
MEMORIES
TPICLK
RESET
TPIDATA
TINY PROGRAMMING INTERFACE (TPI)
DATA BUS
Programming is done via the physical interface. This is a 3-pin interface, which uses the RESET pin as
enable, the TPICLK pin as the clock input, and the TPIDATA pin as data input and output. NVM can be
programmed at 5V, only.
Related Links
MEMPROG- Memory Programming on page 152
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16.3. Physical Layer of Tiny Programming Interface
The TPI physical layer handles the basic low-level serial communication. The TPI physical layer uses a
bi-directional, half-duplex serial receiver and transmitter. The physical layer includes serial-to-parallel and
parallel-to-serial data conversion, start-of-frame detection, frame error detection, parity error detection,
parity generation and collision detection.
The TPI is accessed via three pins, as follows:
•RESET: Tiny Programming Interface enable input
•TPICLK: Tiny Programming Interface clock input
•TPIDATA: Tiny Programming Interface data input/output
In addition, the VCC and GND pins must be connected between the external programmer and the device.
Figure 16-2 Using an External Programmer for In-System Programming via TPI
ATtiny4/5/9/10
TPIDATA/P B0
GND
TPICLK/P B1
PB3/RES ET
VCC
PB2
TPI
CONN
APPLICATION
+5V
NVM can be programmed at 5V, only. In some designs it may be necessary to protect components that
can not tolerate 5V with, for example, series resistors.
16.3.1. Enabling
The following sequence enables the Tiny Programming Interface:
•Apply 5V between VCC and GND
•Depending on the method of reset to be used:
–Either: wait tTOUT (see System and Reset Characteristics) and then set the RESET pin low.
This will reset the device and enable the TPI physical layer. The RESET pin must then be
kept low for the entire programming session
–Or: if the RSTDISBL configuration bit has been programmed, apply 12V to the RESET pin.
The RESET pin must be kept at 12V for the entire programming session
•Wait tRST (see System and Reset Characteristics )
•Keep the TPIDATA pin high for 16 TPICLK cycles
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Figure 16-3 Sequence for enabling the Tiny Programming Interface
RESET
tRST
TPIDATA
TPICLK
16 x TPICLK CYCLES
16.3.2. Disabling
Provided that the NVM enable bit has been cleared, the TPI is automatically disabled if the RESET pin is
released to inactive high state or, alternatively, if VHV is no longer applied to the RESET pin.
If the NVM enable bit is not cleared a power down is required to exit TPI programming mode. See
NVMEN bit in TPISR – Tiny Programming Interface Status Register.
Related Links
TPISR on page 151
16.3.3. Frame Format
The TPI physical layer supports a fixed frame format. A frame consists of one character, eight bits in
length, and one start bit, a parity bit and two stop bits. Data is transferred with the least significant bit first.
Figure 16-4 Serial frame format.
TPIDATA
TPICLK
SP1ST SP2 IDLE/STIDLE PD1D0 D7
Symbols used in the above figure:
•ST: Start bit (always low)
•D0-D7: Data bits (least significant bit sent first)
•P: Parity bit (using even parity)
•SP1: Stop bit 1 (always high)
•SP2: Stop bit 2 (always high)
16.3.4. Parity Bit Calculation
The parity bit is always calculated using even parity. The value of the bit is calculated by doing an
exclusive-or of all the data bits, as follows:
=0 1 2 3 4 5 6 70
where:
•P: Parity bit using even parity
•D0-D7: Data bits of the character
16.3.5. Supported Characters
The BREAK character is equal to a 12 bit long low level. It can be extended beyond a bit-length of 12.
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Figure 16-5 Supported characters.
IDLE/STIDLE
BREAK CHARACTER
DATA CHARACTER
SP1ST SP2 IDLE/STIDLE PD1D0 D7
TPIDATA
TPIDATA
16.3.6. Operation
The TPI physical layer operates synchronously on the TPICLK provided by the external programmer. The
dependency between the clock edges and data sampling or data change is shown in the figure below.
Data is changed at falling edges and sampled at rising edges.
Figure 16-6 Data changing and Data sampling.
TPIDATA
TPICLK
SAMPLE
SETUP
The TPI physical layer supports two modes of operation: Transmit and Receive. By default, the layer is in
Receive mode, waiting for a start bit. The mode of operation is controlled by the access layer.
16.3.7. Serial Data Reception
When the TPI physical layer is in receive mode, data reception is started as soon as a start bit has been
detected. Each bit that follows the start bit will be sampled at the rising edge of the TPICLK and shifted
into the shift register until the second stop bit has been received. When the complete frame is present in
the shift register the received data will be available for the TPI access layer.
There are three possible exceptions in the receive mode: frame error, parity error and break detection. All
these exceptions are signalized to the TPI access layer, which then enters the error state and puts the
TPI physical layer into receive mode, waiting for a BREAK character.
•Frame Error Exception. The frame error exception indicates the state of the stop bit. The frame
error exception is set if the stop bit was read as zero.
•Parity Error Exception. The parity of the data bits is calculated during the frame reception. After the
frame is received completely, the result is compared with the parity bit of the frame. If the
comparison fails the parity error exception is signalized.
•Break Detection Exception. The Break detection exception is given when a complete frame of all
zeros has been received.
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16.3.8. Serial Data Transmission
When the TPI physical layer is ready to send a new frame it initiates data transmission by loading the shift
register with the data to be transmitted. When the shift register has been loaded with new data, the
transmitter shifts one complete frame out on the TPIDATA line at the transfer rate given by TPICLK.
If a collision is detected during transmission, the output driver is disabled. The TPI access layer enters the
error state and the TPI physical layer is put into receive mode, waiting for a BREAK character.
16.3.9. Collision Detection Exception
The TPI physical layer uses one bi-directional data line for both data reception and transmission. A
possible drive contention may occur, if the external programmer and the TPI physical layer drive the
TPIDATA line simultaneously. In order to reduce the effect of the drive contention, a collision detection
mechanism is supported. The collision detection is based on the way the TPI physical layer drives the
TPIDATA line.
The TPIDATA line is driven by a tri-state, push-pull driver with internal pull-up. The output driver is always
enabled when a logical zero is sent. When sending successive logical ones, the output is only driven
actively during the first clock cycle. After this, the output driver is automatically tri-stated and the TPIDATA
line is kept high by the internal pull-up. The output is re-enabled, when the next logical zero is sent.
The collision detection is enabled in transmit mode, when the output driver has been disabled. The data
line should now be kept high by the internal pull-up and it is monitored to see, if it is driven low by the
external programmer. If the output is read low, a collision has been detected.
There are some potential pit-falls related to the way collision detection is performed. For example,
collisions cannot be detected when the TPI physical layer transmits a bit-stream of successive logical
zeros, or bit-stream of alternating logical ones and zeros. This is because the output driver is active all the
time, preventing polling of the TPIDATA line. However, within a single frame the two stop bits should
always be transmitted as logical ones, enabling collision detection at least once per frame (as long as the
frame format is not violated regarding the stop bits).
The TPI physical layer will cease transmission when it detects a collision on the TPIDATA line. The
collision is signalized to the TPI access layer, which immediately changes the physical layer to receive
mode and goes to the error state. The TPI access layer can be recovered from the error state only by
sending a BREAK character.
16.3.10. Direction Change
In order to ensure correct timing of the half-duplex operation, a simple guard time mechanism has been
added to the physical layer. When the TPI physical layer changes from receive to transmit mode, a
configurable number of additional IDLE bits are inserted before the start bit is transmitted. The minimum
transition time between receive and transmit mode is two IDLE bits.
The total IDLE time is the specified guard time plus two IDLE bits. The guard time is configured by
dedicated bits in the TPIPCR register. The default guard time value after the physical layer is initialized is
128 bits.
The external programmer looses control of the TPIDATA line when the TPI target changes from receive
mode to transmit. The guard time feature relaxes this critical phase of the communication. When the
external programmer changes from receive mode to transmit, a minimum of one IDLE bit should be
inserted before the start bit is transmitted.
16.3.11. Access Layer of Tiny Programming Interface
The TPI access layer is responsible for handling the communication with the external programmer. The
communication is based on message format, where each message comprises an instruction followed by
one or more byte-sized operands. The instruction is always sent by the external programmer but
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operands are sent either by the external programmer or by the TPI access layer, depending on the type of
instruction issued.
The TPI access layer controls the character transfer direction on the TPI physical layer. It also handles
the recovery from the error state after exception.
The Control and Status Space (CSS) of the Tiny Programming Interface is allocated for control and status
registers in the TPI access Layer. The CSS consist of registers directly involved in the operation of the
TPI itself. These register are accessible using the SLDCS and SSTCS instructions.
The access layer can also access the data space, either directly or indirectly using the Pointer Register
(PR) as the address pointer. The data space is accessible using the SLD, SST, SIN and SOUT
instructions. The address pointer can be stored in the Pointer Register using the SLDPR instruction.
16.3.11.1. Message format
Each message comprises an instruction followed by one or more byte operands. The instruction is always
sent by the external programmer. Depending on the instruction all the following operands are sent either
by the external programmer or by the TPI.
The messages can be categorized in two types based on the instruction, as follows:
•Write messages. A write message is a request to write data. The write message is sent entirely by
the external programmer. This message type is used with the SSTCS, SST, STPR, SOUT and
SKEY instructions.
•Read messages. A read message is a request to read data. The TPI reacts to the request by
sending the byte operands. This message type is used with the SLDCS, SLD and SIN instructions.
All the instructions except the SKEY instruction require the instruction to be followed by one byte
operand. The SKEY instruction requires 8 byte operands. For more information, see the TPI instruction
set.
16.3.11.2. Exception Handling and Synchronisation
Several situations are considered exceptions from normal operation of the TPI. When the TPI physical
layer is in receive mode, these exceptions are:
•The TPI physical layer detects a parity error.
•The TPI physical layer detects a frame error.
•The TPI physical layer recognizes a BREAK character.
When the TPI physical layer is in transmit mode, the possible exceptions are:
•The TPI physical layer detects a data collision.
All these exceptions are signalized to the TPI access layer. The access layer responds to an exception by
aborting any on-going operation and enters the error state. The access layer will stay in the error state
until a BREAK character has been received, after which it is taken back to its default state. As a
consequence, the external programmer can always synchronize the protocol by simply transmitting two
successive BREAK characters.
16.4. Instruction Set
The TPI has a compact instruction set that is used to access the TPI Control and Status Space (CSS)
and the data space. The instructions allow the external programmer to access the TPI, the NVM
Controller and the NVM memories. All instructions except SKEY require one byte operand following the
instruction. The SKEY instruction is followed by 8 data bytes. All instructions are byte-sized.
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Table 16-1 Instruction Set Summary
Mnemonic Operand Description Operation
SLD data, PR Serial LoaD from data space using indirect addressing data ← DS[PR]
SLD data, PR+ Serial LoaD from data space using indirect addressing and
post-increment data ← DS[PR]
PR ← PR+1
SST PR, data Serial STore to data space using indirect addressing DS[PR] ← data
SST PR+, data Serial STore to data space using indirect addressing and
post-increment DS[PR] ← data
PR ← PR+1
SSTPR PR, a Serial STore to Pointer Register using direct addressing PR[a] ← data
SIN data, a Serial IN from data space data ← I/O[a]
SOUT a, data Serial OUT to data space I/O[a] ← data
SLDCS data, a Serial LoaD from Control and Status space using direct
addressing
data ← CSS[a]
SSTCS a, data Serial STore to Control and Status space using direct
addressing
CSS[a] ← data
SKEY Key, {8{data}} Serial KEY Key ← {8{data}}
16.4.1. SLD - Serial LoaD from data space using indirect addressing
The SLD instruction uses indirect addressing to load data from the data space to the TPI physical layer
shift-register for serial read-out. The data space location is pointed by the Pointer Register (PR), where
the address must have been stored before data is accessed. The Pointer Register is either left
unchanged by the operation, or post-incremented.
Table 16-2 The Serial Load from Data Space (SLD) Instruction
Operation Opcode Remarks Register
data ← DS[PR] 0010 0000 PR ← PR Unchanged
data ← DS[PR] 0010 0100 PR ← PR + 1 Post increment
16.4.2. SST - Serial STore to data space using indirect addressing
The SST instruction uses indirect addressing to store into data space the byte that is shifted into the
physical layer shift register. The data space location is pointed by the Pointer Register (PR), where the
address must have been stored before the operation. The Pointer Register can be either left unchanged
by the operation, or it can be post-incremented.
Table 16-3 The Serial Store to Data Space (SST) Instruction
Operation Opcode Remarks Register
DS[PR] ← data 0110 0000 PR ← PR Unchanged
DS[PR] ← data 0110 0000 PR ← PR + 1 Post increment
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16.4.3. SSTPR - Serial STore to Pointer Register
The SSTPR instruction stores the data byte that is shifted into the physical layer shift register to the
Pointer Register (PR). The address bit of the instruction specifies which byte of the Pointer Register is
accessed.
Table 16-4 The Serial Store to Pointer Register (SSTPR) Instruction
Operation Opcode Remarks
PR[a] ← data 0110 100a Bit ‘a’ addresses Pointer Register byte
16.4.4. SIN - Serial IN from i/o space using direct addressing
The SIN instruction loads data byte from the I/O space to the shift register of the physical layer for serial
read-out. The instuction uses direct addressing, the address consisting of the 6 address bits of the
instruction.
Table 16-5 The Serial IN from i/o space (SIN) Instruction
Operation Opcode Remarks
data ← I/O[a] 0aa1 aaaa Bits marked ‘a’ form the direct, 6-bit address
16.4.5. SOUT - Serial OUT to i/o space using direct addressing
The SOUT instruction stores the data byte that is shifted into the physical layer shift register to the I/O
space. The instruction uses direct addressing, the address consisting of the 6 address bits of the
instruction.
Table 16-6 The Serial OUT to i/o space (SOUT) Instruction
Operation Opcode Remarks
I/O[a] ← data 1aa1 aaaa Bits marked ‘a’ form the direct, 6-bit address
16.4.6. SLDCS - Serial LoaD data from Control and Status space using direct addressing
The SLDCS instruction loads data byte from the TPI Control and Status Space to the TPI physical layer
shift register for serial read-out. The SLDCS instruction uses direct addressing, the direct address
consisting of the 4 address bits of the instruction.
Table 16-7 The Serial Load Data from Control and Status space (SLDCS) Instruction
Operation Opcode Remarks
data ← CSS[a] 1000 aaaa Bits marked ‘a’ form the direct, 4-bit address
16.4.7. SSTCS - Serial STore data to Control and Status space using direct addressing
The SSTCS instruction stores the data byte that is shifted into the TPI physical layer shift register to the
TPI Control and Status Space. The SSTCS instruction uses direct addressing, the direct address
consisting of the 4 address bits of the instruction.
Table 16-8 The Serial STore data to Control and Status space (SSTCS) Instruction
Operation Opcode Remarks
CSS[a] ← data 1100 aaaa Bits marked ‘a’ form the direct, 4-bit address
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16.4.8. SKEY - Serial KEY signaling
The SKEY instruction is used to signal the activation key that enables NVM programming. The SKEY
instruction is followed by the 8 data bytes that includes the activation key.
Table 16-9 The Serial KEY signaling (SKEY) Instruction
Operation Opcode Remarks
Key ← {8[data}} 1110 0000 Data bytes follow after instruction
16.5. Accessing the Non-Volatile Memory Controller
By default, NVM programming is not enabled. In order to access the NVM Controller and be able to
program the non-volatile memories, a unique key must be sent using the SKEY instruction.
Table 16-10 Enable Key for Non-Volatile Memory Programming
Key Value
NVM Program Enable 0x1289AB45CDD888FF
After the key has been given, the Non-Volatile Memory Enable (NVMEN) bit in the TPI Status Register
(TPISR) must be polled until the Non-Volatile memory has been enabled.
NVM programming is disabled by writing a logical zero to the NVMEN bit in TPISR.
16.6. Control and Status Space Register Descriptions
The control and status registers of the Tiny Programming Interface are mapped in the Control and Status
Space (CSS) of the interface. These registers are not part of the I/O register map and are accessible via
SLDCS and SSTCS instructions, only. The control and status registers are directly involved in
configuration and status monitoring of the TPI.
Table 16-11 Summary of Control and Status Registers
Offset Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
0x0F TPIIR Tiny Programming Interface Identification Code
0x0E
...
0x03
Reserved - - - - - - - -
0x02 TPIPCR - - - - - GT2 GT1 GT0
0x01 Reserved - - - - - - - -
0x00 TPISR - - - - - - NVMEN -
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16.6.1. Tiny Programming Interface Identification Register
Name: TPIIR
Offset:
Reset: 0x00
Property:
CSS: 0x0F
Bit 7 6 5 4 3 2 1 0
TPIIC[7:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bits 7:0 – TPIIC[7:0]: Tiny Programming Interface Identification Code
These bits give the identification code for the Tiny Programming Interface. The code can be used be the
external programmer to identify the TPI.
Table 16-12 Identification Code for Tiny Programming Interface
Code Value
Interface Identification 0x80
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16.6.2. Tiny Programming Interface Physical Layer Control Register
Name: TPIPCR
Offset:
Reset: 0x00
Property:
CSS: 0x02
Bit 7 6 5 4 3 2 1 0
GT2 GT1 GT0
Access R/W R/W R/W
Reset 0 0 0
Bits 2:0 – GTn: Guard Time [n=2:0]
These bits specify the number of additional IDLE bits that are inserted to the idle time when changing
from reception mode to transmission mode. Additional delays are not inserted when changing from
transmission mode to reception.
The total idle time when changing from reception to transmission mode is Guard Time plus two IDLE bits.
Table 16-13 Identification Code for Tiny Programming Interface
GT2 GT1 GT0 Guard Time (Number of IDLE bits)
0 0 0 +128 (default value)
0 0 1 +64
0 1 0 +32
0 1 1 +16
1 0 0 +8
1 0 1 +4
1 1 0 +2
1 1 1 +0
The default Guard Time is 128 IDLE bits. To speed up the communication, the Guard Time should be set
to the shortest safe value.
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16.6.3. Tiny Programming Interface Status Register
Name: TPISR
Offset:
Reset: 0x00
Property:
CSS: 0x00
Bit 7 6 5 4 3 2 1 0
NVMEN
Access R/W
Reset 0
Bit 1 – NVMEN: Non-Volatile Memory Programming Enabled
NVM programming is enabled when this bit is set. The external programmer can poll this bit to verify the
interface has been successfully enabled.
NVM programming is disabled by writing this bit to zero.
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17. MEMPROG- Memory Programming
17.1. Features
•Two Embedded Non-Volatile Memories:
–Non-Volatile Memory Lock bits (NVM Lock bits)
–Flash Memory
•Four Separate Sections Inside Flash Memory:
–Code Section (Program Memory)
–Signature Section
–Configuration Section
–Calibration Section
•Read Access to All Non-Volatile Memories from Application Software
•Read and Write Access to Non-Volatile Memories from External programmer:
–Read Access to All Non-Volatile Memories
–Write Access to NVM Lock Bits, Flash Code Section and Flash Configuration Section
•External Programming:
–Support for In-System and Mass Production Programming
–Programming Through the Tiny Programming Interface (TPI)
•High Security with NVM Lock Bits
17.2. Overview
The Non-Volatile Memory (NVM) Controller manages all access to the Non-Volatile Memories. The NVM
Controller controls all NVM timing and access privileges, and holds the status of the NVM.
During normal execution the CPU will execute code from the code section of the Flash memory (program
memory). When entering sleep and no programming operations are active, the Flash memory is disabled
to minimize power consumption.
All NVM are mapped to the data memory. Application software can read the NVM from the mapped
locations of data memory using load instruction with indirect addressing.
The NVM has only one read port and, therefore, the next instruction and the data can not be read
simultaneously. When the application reads data from NVM locations mapped to the data space, the data
is read first before the next instruction is fetched. The CPU execution is here delayed by one system
clock cycle.
Internal programming operations to NVM have been disabled and the NVM therefore appears to the
application software as read-only. Internal write or erase operations of the NVM will not be successful.
The method used by the external programmer for writing the Non-Volatile Memories is referred to as
external programming. External programming can be done both in-system or in mass production. The
external programmer can read and program the NVM via the Tiny Programming Interface (TPI).
In the external programming mode all NVM can be read and programmed, except the signature and the
calibration sections which are read-only.
NVM can be programmed at 5V, only.
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17.3. Non-Volatile Memories (NVM)
The device has the following, embedded NVM:
•Non-Volatile Memory Lock Bits
•Flash memory with four separate sections
17.3.1. Non-Volatile Memory Lock Bits
The device provides two Lock Bits.
Table 17-1 Lock Bit Byte
Lock Bit Byte Bit No. Description Default Value
7 1 (unprogrammed)
6 1 (unprogrammed)
5 1 (unprogrammed)
4 1 (unprogrammed)
3 1 (unprogrammed)
2 1 (unprogrammed)
NVLB2 1 Non-Volatile Lock Bit 1 (unprogrammed)
NVLB1 0 Non-Volatile Lock Bit 1 (unprogrammed)
The Lock Bits can be left unprogrammed ("1") or can be programmed ("0") to obtain the additional
security. Lock Bits can be erased to "1" with the Chip Erase command, only.
Table 17-2 Lock Bit Protection Modes
Memory Lock Bits(1) Protection Type
LB Mode NVLB2(2) NVLB1(2)
1 1 1 No memory lock features enabled.
2 1 0 Further Programming of the Flash memory is disabled in the external
programming mode. The configuration section bits are locked in the
external programming mode
3 0 0 Further programming and verification of the flash is disabled in the
external programming mode. The configuration section bits are locked
in the external programming mode
Note:
1. Program the configuration section bits before programming NVLB1 and NVLB2.
2. "1" means unprogrammed, "0" means programmed
17.3.2. Flash Memory
The embedded Flash memory has four separate sections.
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Table 17-3 Number of Words and Pages in the Flash (ATtiny9/10)
Section Size (Bytes) Page Size
(Words)
Pages WADDR PADDR
Code (program
memory)
1024 8 64 [3:1] [9:4]
Configuration 8 8 1 [3:1] -
Signature (1) 16 8 2 [3:1] [4:4]
Calibration(1) 8 8 1 [3:1] -
Note:
1. This section is read-only.
Table 17-4 Number of Words and Pages in the Flash (ATtiny4/5)
Section Size (Bytes) Page Size
(Words)
Pages WADDR PADDR
Code (program
memory)
512 8 32 [3:1] [9:4]
Configuration 8 8 1 [3:1] -
Signature (1) 16 8 2 [3:1] [4:4]
Calibration(1) 8 8 1 [3:1] -
Note:
1. This section is read-only.
17.3.3. Configuration Section
ATtiny4/5/9/10 have one configuration byte, which resides in the configuration section.
Table 17-5 Configuration bytes
Configuration word address Configuration word data
High byte Low byte
0x00 Reserved Configuration Byte 0
0x01 ... 0x07 Reserved Reserved
The next table briefly describes the functionality of all configuration bits and how they are mapped into the
configuration byte.
Table 17-6 Configuration Byte 0
Bit Description Default Value
7:3 – Reserved 1 (unprogrammed)
2 CKOUT System Clock Output 1 (unprogrammed)
1 WDTON Watchdog Timer always on 1 (unprogrammed)
0 RSTDISBL External Reset disable 1 (unprogrammed)
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Configuration bits are not affected by a chip erase but they can be cleared using the configuration section
erase command (see Erasing the Configuration Section in this chapter). Note that configuration bits are
locked if Non- Volatile Lock Bit 1 (NVLB1) is programmed.
17.3.3.1. Latching of Configuration Bits
All configuration bits are latched either when the device is reset or when the device exits the external
programming mode. Changes to configuration bit values have no effect until the device leaves the
external programming mode.
17.3.4. Signature Section
The signature section is a dedicated memory area used for storing miscellaneous device information,
such as the device signature. Most of this memory section is reserved for internal use.
Table 17-7 Signature bytes
Signature word address Configuration word data
High byte Low byte
0x00 Device ID 1 Manufacturer ID
0x01 Reserved for internal use Device ID 2
0x02 ... 0x0F Reserved for internal use Reserved for internal use
ATtiny4/5/9/10 have a three-byte signature code, which can be used to identify the device. The three
bytes reside in the signature section, as shown in the above table. The signature data for ATtiny4/5/9/10
is given in the next table.
Table 17-8 Signature codes
Part Signature Bytes
Manufacturer ID Device ID 1 Device ID 2
ATtiny4 0x1E 0x8F 0x0A
ATtiny5 0x1E 0x8F 0x09
ATtiny9 0x1E 0x90 0x08
ATtiny10 0x1E 0x90 0x03
17.3.5. Calibration Section
ATtiny4/5/9/10 have one calibration byte. The calibration byte contains the calibration data for the internal
oscillator and resides in the calibration section. During reset, the calibration byte is automatically written
into the OSCCAL register to ensure correct frequency of the calibrated internal oscillator.
Table 17-9 Calibration byte
Calibration word address Configuration word data
High byte Low byte
0x00 Reserved Internal oscillator calibration value
0x01 ... 0x07 Reserved Reserved
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17.3.5.1. Latching of Calibration Value
To ensure correct frequency of the calibrated internal oscillator the calibration value is automatically
written into the OSCCAL register during reset.
17.4. Accessing the NVM
NVM lock bits, and all Flash memory sections are mapped to the data space as shown in Data Memory.
The NVM can be accessed for read and programming via the locations mapped in the data space.
The NVM Controller recognizes a set of commands that can be used to instruct the controller what type of
programming task to perform on the NVM. Commands to the NVM Controller are issued via the NVM
Command Register. See NVMCMD - Non-Volatile Memory Command Register. After the selected
command has been loaded, the operation is started by writing data to the NVM locations mapped to the
data space.
When the NVM Controller is busy performing an operation it will signal this via the NVM Busy Flag in the
NVM Control and Status Register. See NVMCSR - Non-Volatile Memory Control and Status Register. The
NVM Command Register is blocked for write access as long as the busy flag is active. This is to ensure
that the current command is fully executed before a new command can start.
Programming any part of the NVM will automatically inhibit the following operations:
•All programming to any other part of the NVM
•All reading from any NVM location
ATtiny4/5/9/10 support only external programming. Internal programming operations to NVM have been
disabled, which means any internal attempt to write or erase NVM locations will fail.
Related Links
SRAM Data Memory on page 25
NVMCMD on page 161
NVMCSR on page 160
17.4.1. Addressing the Flash
The data space uses byte accessing but since the Flash sections are accessed as words and organized
in pages, the byte-address of the data space must be converted to the word-address of the Flash section.
The most significant bits of the data space address select the NVM Lock bits or the Flash section mapped
to the data memory. The word address within a page (WADDR) is held by bits [WADDRMSB:1], and the
page address (PADDR) by bits [PADDRMSB:WADDRMSB+1]. Together, PADDR and WADDR form the
absolute address of a word in the Flash section.
The least significant bit of the Flash section address is used to select the low or high byte of the word.
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Figure 17-1 Addressing the Flash Memory
00
PAGE
01
02
SECTIONEND
WORD
00
01
PAGEEND
FLASH
SECTION FLAS H
PAGE
0/1WADDRPADDR
1WADDRMSBPADDRMS B16
ADDRESS POINTER
...
...
...
...
...
...
PAGE ADDR ES S
W ITHIN A FLAS H
S ECTION
W OR D ADDR ES S
W ITHIN A FLAS H
PAGE
LOW /HIGH
BY TE S ELECT
WADDRMSB+1
17.4.2. Reading the Flash
The Flash can be read from the data memory mapped locations one byte at a time. For read operations,
the least significant bit (bit 0) is used to select the low or high byte in the word address. If this bit is zero,
the low byte is read, and if it is one, the high byte is read.
17.4.3. Programming the Flash
The Flash can be written word-by-word. Before writing a Flash word, the Flash target location must be
erased. Writing to an un-erased Flash word will corrupt its content.
The Flash is word-accessed for writing, and the data space uses byte-addressing to access Flash that
has been mapped to data memory. It is therefore important to write the word in the correct order to the
Flash, namely low bytes before high bytes. First, the low byte is written to the temporary buffer. Then,
writing the high byte latches both the high byte and the low byte into the Flash word buffer, starting the
write operation to Flash.
The Flash erase operations can only performed for the entire Flash sections.
The Flash programming sequence is as follows:
1. Perform a Flash section erase or perform a Chip erase
2. Write the Flash section word by word
17.4.3.1. Chip Erase
The Chip Erase command will erase the entire code section of the Flash memory and the NVM Lock Bits.
For security reasons, the NVM Lock Bits are not reset before the code section has been completely
erased. Configuration, Signature and Calibration sections are not changed.
Before starting the Chip erase, the NVMCMD register must be loaded with the CHIP_ERASE command.
To start the erase operation a dummy byte must be written into the high byte of a word location that
resides inside the Flash code section. The NVMBSY bit remains set until erasing has been completed.
While the Flash is being erased neither Flash buffer loading nor Flash reading can be performed.
The Chip Erase can be carried out as follows:
1. Write the 0x10 (CHIP_ERASE) to the NVMCMD register
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2. Start the erase operation by writing a dummy byte to the high byte of any word location inside the
code section
3. Wait until the NVMBSY bit has been cleared
Related Links
NVMCMD on page 161
17.4.3.2. Erasing the Code Section
The algorithm for erasing all pages of the Flash code section is as follows:
1. Write the 0x14 (SECTION_ERASE) to the NVMCMD register
2. Start the erase operation by writing a dummy byte to the high byte of any word location inside the
code section
3. Wait until the NVMBSY bit has been cleared
Related Links
NVMCMD on page 161
17.4.3.3. Writing a Code Word
The algorithm for writing a word to the code section is as follows:
1. Write the 0x1D (WORD_WRITE) to the NVMCMD register
2. Write the low byte of the data into the low byte of a word location
3. Write the high byte of the data into the high byte of the same word location. This will start the Flash
write operation
4. Wait until the NVMBSY bit has been cleared
Related Links
NVMCMD on page 161
17.4.3.4. Erasing the Configuration Section
The algorithm for erasing the Configuration section is as follows:
1. Write the 0x14 (SECTION_ERASE) to the NVMCMD register
2. Start the erase operation by writing a dummy byte to the high byte of any word location inside the
configuration section
3. Wait until the NVMBSY bit has been cleared
Related Links
NVMCMD on page 161
17.4.3.5. Writing a Configuration Word
The algorithm for writing a Configuration word is as follows:
1. Write the 0x1D (WORD_WRITE) to the NVMCMD register
2. Write the low byte of the data to the low byte of a configuration word location
3. Write the high byte of the data to the high byte of the same configuration word location. This will
start the Flash write operation.
4. Wait until the NVMBSY bit has been cleared
Related Links
NVMCMD on page 161
17.4.4. Reading NVM Lock Bits
The Non-Volatile Memory Lock Byte can be read from the mapped location in data memory.
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17.4.5. Writing NVM Lock Bits
The algorithm for writing the Lock bits is as follows:
1. Write the WORD_WRITE command to the NVMCMD register.
2. Write the lock bits value to the Non-Volatile Memory Lock Byte location. This is the low byte of the
Non- Volatile Memory Lock Word.
3. Start the NVM Lock Bit write operation by writing a dummy byte to the high byte of the NVM Lock
Word location.
4. Wait until the NVMBSY bit has been cleared.
Related Links
NVMCMD on page 161
17.5. Self programming
The ATtiny4/5/9/10 don't support internal programming.
17.6. External Programming
The method for programming the Non-Volatile Memories by means of an external programmer is referred
to as external programming. External programming can be done both in-system or in mass production.
The Non-Volatile Memories can be externally programmed via the Tiny Programming Interface (TPI). For
details on the TPI, see Programming interface. Using the TPI, the external programmer can access the
NVM control and status registers mapped to I/O space and the NVM memory mapped to data memory
space.
Related Links
Programming interface on page 140
17.6.1. Entering External Programming Mode
The TPI must be enabled before external programming mode can be entered. The following procedure
describes, how to enter the external programming mode after the TPI has been enabled:
1. Make a request for enabling NVM programming by sending the NVM memory access key with the
SKEY instruction.
2. Poll the status of the NVMEN bit in TPISR until it has been set.
Refer to the Programming Interface description for more detailed information of enabling the TPI and
programming the NVM.
Related Links
Programming interface on page 140
17.6.2. Exiting External Programming Mode
Clear the NVM enable bit to disable NVM programming, then release the RESET pin.
See NVMEN bit in TPISR – Tiny Programming Interface Status Register.
Related Links
TPISR on page 151
17.7. Register Description
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17.7.1. Non-Volatile Memory Control and Status Register
Name: NVMCSR
Offset: 0x32
Reset: 0x00
Property:
-
Bit 7 6 5 4 3 2 1 0
NVMBSY
Access R/W
Reset 0
Bit 7 – NVMBSY: Non-Volatile Memory Busy
This bit indicates the NVM memory (Flash memory and Lock Bits) is busy, being programmed. This bit is
set when a program operation is started, and it remains set until the operation has been completed.
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17.7.2. Non-Volatile Memory Command Register
Name: NVMCMD
Offset: 0x33
Reset: 0x00
Property:
-
Bit 7 6 5 4 3 2 1 0
NVMCMD[5:0]
Access R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0
Bits 5:0 – NVMCMD[5:0]: Non-Volatile Memory Command
These bits define the programming commands for the flash.
Table 17-10 NVM Programming commands
Operation Type NVMCMD Mnemonic Description
Binary Hex
General 0b000000 0x00 NO_OPERATION No operation
0b010000 0x10 CHIP_ERASE Chip erase
Section 0b010100 0x14 SECTION_ERASE Section erase
Word 0b011101 0x1D WORD_WRITE Word write
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18. Electrical Characteristics
18.1. Absolute Maximum Ratings*
Operating Temperature -55°C to +125°C
Storage Temperature -65°C to +150°C
Voltage on any Pin except RESET
with respect to Ground
-0.5V to VCC+0.5V
Voltage on RESET with respect to Ground -0.5V to +13.0V
Maximum Operating Voltage 6.0V
DC Current per I/O Pin 40.0 mA
DC Current VCC and GND Pins 200.0 mA
Note: Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage
to the device. This is a stress rating only and functional operation of the device at these or other
conditions beyond those indicated in the operational sections of this specification is not implied. Exposure
to absolute maximum rating conditions for extended periods may affect device reliability.
18.2. DC Characteristics
Table 18-1 DC Characteristics. TA = -40°C to +85°C
Symbol Parameter Condition Min. Typ. Max. Units
VIL Input Low Voltage VCC = 1.8V - 2.4V
VCC = 2.4V - 5.5V
-0.5 0.2VCC
0.3VCC
V
VIH Input High-voltage
Except RESET pin
VCC = 1.8V - 2.4V
VCC = 2.4V - 5.5V
0.7VCC(1)
0.6VCC(1)
VCC +0.5(2) V
Input High-voltage
RESET pin
VCC = 1.8V to 5.5V 0.9VCC(1) VCC +0.5(2) V
VOL Output Low Voltage(3)
Except RESET pin(5)
IOL = 10 mA, VCC = 5V
IOL = 5 mA, VCC = 3V
0.6
0.5
V
VOH Output High-voltage(4)
Except RESET pin(5)
IOH = -10 mA, VCC = 5
V
IOH = -5 mA, VCC = 3V
4.3
2.5
V
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Symbol Parameter Condition Min. Typ. Max. Units
ILIL Input Leakage
Current I/O Pin
VCC = 5.5V, pin low
(absolute value)
<0.05 1 µA
ILIH Input Leakage
Current I/O Pin
VCC = 5.5V, pin high
(absolute value)
<0.05 1 µA
RRST Reset Pull-up Resistor VCC = 5.5V, input low 30 60 kΩ
RPU I/O Pin Pull-up Resistor VCC = 5.5V, input low 20 50 kΩ
IACLK Analog Comparator Input
Leakage Current VCC = 5V
Vin = VCC/2
-50 50 nA
ICC Power Supply Current(6) Active 1MHz, VCC = 2V 0.2 0.5 mA
Active 4MHz, VCC = 3V 0.8 1.2 mA
Active 8MHz, VCC = 5V 2.7 4 mA
Idle 1MHz, VCC = 2V 0.02 0.2 mA
Idle 4MHz, VCC = 3V 0.13 0.5 mA
Idle 8MHz, VCC = 5V 0.6 1.5 mA
Power-down mode(7) WDT enabled, VCC = 3V 4.5 10 µA
WDT disabled, VCC = 3V 0.15 2 µA
Note:
1. “Min” means the lowest value where the pin is guaranteed to be read as high.
2. “Max” means the highest value where the pin is guaranteed to be read as low.
3. Although each I/O port can sink more than the test conditions (10 mA at VCC = 5V, 5 mA at VCC =
3V) under steady state conditions (non-transient), the sum of all IOL (for all ports) should not exceed
60 mA. If IOL exceeds the test conditions, VOL may exceed the related specification. Pins are not
guaranteed to sink current greater than the listed test condition.
4. Although each I/O port can source more than the test conditions (10 mA at VCC = 5V, 5 mA at VCC
= 3V) under steady state conditions (non-transient), the sum of all IOH (for all ports) should not
exceed 60 mA. If IOH exceeds the test condition, VOH may exceed the related specification. Pins are
not guaranteed to source current greater than the listed test condition.
5. The RESET pin must tolerate high voltages when entering and operating in programming modes
and, as a consequence, has a weak drive strength as compared to regular I/O pins. See Figure
19-25 Reset Pin as I/O, Output Voltage vs. Sink Current on page 182, and Figure 19-26 Reset Pin
as I/O, Output Voltage vs. Source Current on page 182.
6. Values are with external clock using methods described in Minimizing Power Consumption. Power
Reduction is enabled (PRR = 0xFF) and there is no I/O drive.
7. BOD Disabled.
Related Links
Minimizing Power Consumption on page 42
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18.3. Speed
The maximum operating frequency of the device depends on VCC . The relationship between supply
voltage and maximum operating frequency is piecewise linear.
Figure 18-1 Maximum Frequency vs. VCC
4 MHz
8 MHz
1.8V 5.5V
4.5V2.7V
12 MHz
18.4. Clock Characteristics
18.4.1. Accuracy of Calibrated Internal Oscillator
It is possible to manually calibrate the internal oscillator to be more accurate than default factory
calibration. Note that the oscillator frequency depends on temperature and voltage. Voltage and
temperature characteristics can be found in Figure 19-39 Calibrated Oscillator Frequency vs. VCC on
page 189 and Figure 19-40 Calibrated Oscillator Frequency vs. Temperature on page 189
Table 18-2 Calibration Accuracy of Internal RC Oscillator
Calibration
Method
Target Frequency VCC Temperature Accuracy at given
Voltage &
Temperature(1)
Factory
Calibration
8.0 MHz 3V 25°C ±10%
User
Calibration
Fixed frequency within:
7.3 - 8.1 MHz
Fixed voltage
within:
1.8V - 5.5V
Fixed temp. within:
-40°C - 85°C
±1%
Note:
1. Accuracy of oscillator frequency at calibration point (fixed temperature and fixed voltage).
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18.4.2. External Clock Drive
Figure 18-2 External Clock Drive Waveform
VIL1
VIH1
Table 18-3 External Clock Drive Characteristics
Symbol Parameter VCC = 1.8 - 5.5V VCC = 2.7 - 5.5V VCC = 4.5 - 5.5V Units
Min. Max. Min. Max. Min. Max.
1/tCLCL Clock Frequency 0 4 0 8 0 12 MHz
tCLCL Clock Period 250 125 83 ns
tCHCX High Time 100 50 33 ns
tCLCX Low Time 100 50 33 ns
tCLCH Rise Time 2.0 1 0.6 μs
tCHCL Fall Time 2.0 1 0.6 μs
ΔtCLCL Change in period from one clock
cycle to the next
2 2 2 %
18.5. System and Reset Characteristics
Table 18-4 Reset, VLM, and Internal Voltage Characteristics
Symbol Parameter Condition Min(1) Typ(1) Max(1) Units
VRST RESET Pin Threshold Voltage 0.2 VCC 0.9VCC V
tRST Minimum pulse width on RESET Pin VCC = 1.8V
VCC = 3V
VCC = 5V
2000
700
400
ns
tTOUT Time-out after reset 32 64 128 ms
Note:
1. Values are guidelines, only
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18.5.1. Power-On Reset
Table 18-5 Characteristics of Enhanced Power-On Reset. TA = -40 - 85°C
Symbol Parameter Min(1) Typ(1) Max(1) Units
VPOR Release threshold of power-on reset (2) 1.1 1.4 1.6 V
VPOA Activation threshold of power-on reset (3) 0.6 1.3 1.6 V
SRON Power-On Slope Rate 0.01 V/ms
Note:
1. Values are guidelines, only
2. Threshold where device is released from reset when voltage is rising
3. The Power-on Reset will not work unless the supply voltage has been below VPOA
18.5.2. VCC Level Monitor
Table 18-6 Voltage Level Monitor Thresholds
Parameter Min Typ (1) Max Units
Trigger level VLM1L 1.1 1.4 1.6 V
Trigger level VLM1H 1.4 1.6 1.8
Trigger level VLM2 2.0 2.5 2.7
Trigger level VLM3 3.2 3.7 4.5
Settling time VMLM2,VLM3 (VLM1H,VLM1L) 5 (50) µs
Note:
1. Typical values at room temperature
18.6. Analog Comparator Characteristics
Table 18-7 Analog Comparator Characteristics, TA = -40°C - 85°C
Symbol Parameter Condition Min Typ Max Units
VAIO Input Offset Voltage VCC = 5V, VIN = VCC / 2 < 10 40 mV
ILAC Input Leakage Current VCC = 5V, VIN = VCC / 2 -50 50 nA
tAPD Analog Propagation Delay
(from saturation to slight overdrive)
VCC = 2.7V 750 ns
VCC = 4.0V 500
Analog Propagation Delay
(large step change)
VCC = 2.7V 100
VCC = 4.0V 75
tDPD Digital Propagation Delay VCC = 1.8V - 5.5 1 2 CLK
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18.7. ADC Characteristics (ATtiny5/10, only)
Table 18-8 ADC Characteristics. T = -40°C - 85°C. VCC = 2.5V - 5.5V
Symbol Parameter Condition Min Typ Max Units
Resolution 8 Bits
Absolute accuracy
(Including INL, DNL, and
Quantization, Gain and Offset
Errors)
VREF = VCC = 4V,
ADC clock = 200 kHz
1.0 LSB
VREF = VCC = 4V, ADC clock = 200
kHz
Noise Reduction Mode
1.0 LSB
Integral Non-Linearity (INL)
(Accuracy after Offset and
Gain Calibration)
VREF = VCC = 4V,
ADC clock = 200 kHz
1.0 LSB
Differential Non-linearity (DNL) VREF = VCC = 4V, ADC clock = 200
kHz
0.5 LSB
Gain Error VREF = VCC = 4V, ADC clock = 200
kHz
1.0 LSB
Offset Error VREF = VCC = 4V, ADC clock = 200
kHz
1.0 LSB
Conversion Time Free Running Conversion 65 260 µs
Clock Frequency 50 200 kHz
VIN Input Voltage GND VREF V
Input Bandwidth 7.7 kHz
RAIN Analog Input Resistance 100 MΩ
ADC Conversion Output 0 255 LSB
18.8. Serial Programming Characteristics
Figure 18-3 Serial Programming Timing
tCHIX
TPIDATA
tIVCH
tCHCL
tCLCH
tCLCL
TPICLK
tCLOV
Tra nsmit ModeRece ive Mode
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Table 18-9 Serial Programming Characteristics, TA = -40°C to 85°C, VCC = 5V ± 5% (Unless Otherwise Noted)
Symbol Parameter Min Typ Max Units
1/tCLCL Clock Frequency 2 MHz
tCLCL Clock Period 500 ns
tCLCH Clock Low Pulse Width 200 ns
tCHCH Clock High Pulse Width 200 ns
tIVCH Data Input to Clock High Setup Time 50 ns
tCHIX Data Input Hold Time After Clock High 100 ns
tCLOV Data Output Valid After Clock Low Time 200 ns
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19. Typical Characteristics
The data contained in this section is largely based on simulations and characterization of similar devices
in the same process and design methods. Thus, the data should be treated as indications of how the part
will behave.
The following charts show typical behavior. These figures are not tested during manufacturing. During
characterisation devices are operated at frequencies higher than test limits but they are not guaranteed to
function properly at frequencies higher than the ordering code indicates.
All current consumption measurements are performed with all I/O pins configured as inputs and with
internal pull-ups enabled. Current consumption is a function of several factors such as operating voltage,
operating frequency, loading of I/O pins, switching rate of I/O pins, code executed and ambient
temperature. The dominating factors are operating voltage and frequency.
A sine wave generator with rail-to-rail output is used as clock source but current consumption in Power-
Down mode is independent of clock selection. The difference between current consumption in Power-
Down mode with Watchdog Timer enabled and Power-Down mode with Watchdog Timer disabled
represents the differential current drawn by the Watchdog Timer.
The current drawn from pins with a capacitive load may be estimated (for one pin) as follows:
ICP VCC × CL× fSW
where VCC = operating voltage, CL = load capacitance and fSW = average switching frequency of I/O pin.
19.1. Supply Current of I/O Modules
Tables and formulas below can be used to calculate additional current consumption for the different I/O
modules in Active and Idle mode. Enabling and disabling of I/O modules is controlled by the Power
Reduction Register. See Power Reduction Register for details.
Table 19-1 Additional Current Consumption for the different I/O modules (absolute values)
PRR bit Typical numbers
VCC = 2V, f = 1MHz VCC = 3V, f = 4MHz VCC = 5V, f = 8MHz
PRTIM0 6.6 uA 40.0 uA 153.0 uA
PRADC (1) 29.6 uA 88.3 uA 333.3 uA
Note: 1. The ADC is available in ATtiny5/10, only
The table below can be used for calculating typical current consumption for other supply voltages and
frequencies than those mentioned in the table above.
Table 19-2 Additional Current Consumption (percentage) in Active and Idle mode
PRR bit Current consumption additional to active
mode with external clock
(see Figure 17-1 and Figure 17-2)
Current consumption additional to idle
mode with external clock
(see Figure 17-7 and Figure 17-8)
PRTIM0 2.3 % 10.4 %
PRADC (1) 6.7 % 28.8 %
Note: 1. The ADC is available in ATtiny5/10, only
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Related Links
Power Reduction Register on page 41
19.2. Active Supply Current
Figure 19-1 Active Supply Current vs. Low Frequency (0.1 - 1.0 MHz)
ACTIVE S UP PLY CURRENT vs . LOW FREQUENCY
(PRR=0xFF)
5.5 V
5.0 V
4.5 V
4.0 V
3.3 V
2.7 V
1.8 V
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
Fre que ncy (MHz)
ICC (mA)
Figure 19-2 Active Supply Current vs. frequency (1 - 12 MHz)
5.5 V
5.0 V
4.5 V
4.0 V
3.3 V
2.7 V
1.8 V
ACTIVE S UP PLY CURRENT vs . FREQUENCY
(PRR=0xFF)
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
5
0 2 4 6 8 10 12
Fre que ncy (MHz)
ICC (mA)
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Figure 19-3 Active Supply Current vs. VCC (Internal Oscillator, 8 MHz)
ACTIVE S UP P LY CURRENT vs . VCC
INTERNAL OS CILLATOR, 8 MHz
85 °C
25 °C
-40 °C
0
0.5
1
1.5
2
2.5
3
3.5
1.5 2 2.5 3 3.5 4 4.5 5 5.5
VCC (V)
ICC (mA)
Figure 19-4 Active Supply Current vs. VCC (Internal Oscillator, 1 MHz)
ACTIVE SUP P LY CURRENT vs . VCC
INTERNAL OS CILLATOR, 1 MHz
85 °C
25 °C
-40 °C
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
1.5 2 2.5 3 3.5 4 4.5 5 5.5
VCC (V)
ICC (mA)
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Figure 19-5 Active Supply Current vs. VCC (Internal Oscillator, 128 kHz)
ACTIVE SUPP LY CURRENT vs . VCC
INTERNAL OS CILLATOR, 128 KHz
85 °C
25 °C
-40 °C
0
0.02
0.04
0.06
0.08
0.1
0.12
1.5 2 2.5 3 3.5 4 4.5 5 5.5
VCC (V)
ICC (mA)
Figure 19-6 Active Supply Current vs. VCC (External Clock, 32 kHz)
ACTIVE SUPP LY CURRENT vs . VCC
INTERNAL OS CILLATOR, 32 KHz
85 °C
25 °C
-40 °C
0
0.005
0.01
0.015
0.02
0.025
0.03
0.035
0.04
1.5 2 2.5 3 3.5 4 4.5 5 5.5
VCC (V)
ICC (mA)
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19.3. Idle Supply Current
Figure 19-7 Idle Supply Current vs. Low Frequency (0.1 - 1.0 MHz)
IDLE SUPPLY CURRENT vs. LOW FREQUENCY
(PRR=0xFF)
5.5 V
5.0 V
4.5 V
4.0 V
3.3 V
2.7 V
1.8 V
0
0,01
0,02
0,03
0,04
0,05
0,06
0,07
0,08
0,09
0,1
0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8 0,9 1
Frequency (MHz)
ICC (mA)
Figure 19-8 Idle Supply Current vs. Frequency (1 - 12 MHz)
5.5 V
5.0 V
4.5 V
4.0 V
3.3 V
2.7 V
1.8 V
IDLE SUPPLY CURRENT vs. FREQUENCY
(PRR=0xFF)
0
0,2
0,4
0,6
0,8
1
210186420
Frequency (MHz)
ICC (mA)
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Figure 19-9 Idle Supply Current vs. VCC (Internal Oscillator, 8 MHz)
IDLE SUPPLY CURRENT vs. VCC
INTERNAL RC OSCILLATOR, 8 MHz
85 °C
25 °C
-40 °C
0
0,1
0,2
0,3
0,4
0,5
0,6
0,7
1,5 2 2,5 3 3,5 4 4,5 5 5,5
VCC (V)
ICC (mA)
Figure 19-10 Idle Supply Current vs. VCC (Internal Oscillator, 1 MHz)
IDLE SUPPLY CURRENT vs. VCC
INTERNAL RC OSCILLATOR, 1 MHz
85 °C
25 °C
-40 °C
0
0,1
0,2
0,3
0,4
0,5
0,6
0,7
1,5 2 2,5 3 3,5 4 4,5 5 5,5
VCC (V)
ICC (mA)
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19.4. Power-down Supply Current
Figure 19-11 Power-down Supply Current vs. VCC (Watchdog Timer Disabled)
POWER-DOWN SUP P LY CURRENT vs. VCC
WATCHDOG TIMER DISABLED
85 °C
25 °C
-40 °C
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45
0.5
1.5 2 2.5 3 3.5 4 4.5 5 5.5
VCC (V)
ICC (uA)
Figure 19-12 Power-down Supply Current vs. VCC (Watchdog Timer Enabled)
POWER-DOWN SUPPLY CURRENT vs. VCC
WATCHDOG TIMER ENABLED
85 °C
25 °C
-40 °C
0
1
2
3
4
5
6
7
8
9
1,5 2 2,5 3 3,5 4 4,5 5 5,5
VCC (V)
ICC (uA)
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19.5. Pin Pull-up
Figure 19-13 I/O pin Pull-up Resistor Current vs. Input Voltage (VCC = 1.8V)
I/O PIN PULL-UP RESISTOR CURRENT vs. INPUT VOLTAGE
85 °C
25 °C
-40 °C
0
10
20
30
40
50
60
0 0,2 0,4 0,6 0,8 1 1,2 1,4 1,6 1,8 2
VOP (V)
IOP (uA)
Figure 19-14 I/O Pin Pull-up Resistor Current vs. input Voltage (VCC = 2.7V)
I/O PIN PULL-UP RESISTOR CURRENT vs. INPUT VOLTAGE
85 °C
25 °C
-40 °C
0
10
20
30
40
50
60
70
80
35
,
2
2
5,115,00
VOP (V)
IOP (uA)
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Figure 19-15 I/O pin Pull-up Resistor Current vs. Input Voltage (VCC = 5V)
I/O PIN PULL-UP RESISTOR CURRENT vs. INPUT VOLTAGE
85 °C
25 °C
-40 °C
0
20
40
60
80
100
120
140
160
6543210
VOP (V)
IOP (uA)
Figure 19-16 Reset Pull-up Resistor Current vs. Reset Pin Voltage (VCC = 1.8V)
RESET PULL-UP RESISTOR CURRENT vs. RESET PIN VOLTAGE
85 °C
25 °C
-40 °C
0
5
10
15
20
25
30
35
40
0 0,2 0,4 0,6 0,8 1 1,2 1,4 1,6 1,8 2
VRESET (V)
IRESET (uA)
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Figure 19-17 Reset Pull-up Resistor Current vs. Reset Pin Voltage (VCC = 2.7V)
RESET PULL-UP RESISTOR CURRENT vs. RESET PIN VOLTAGE
85 °C
25 °C
-40 °C
0
10
20
30
40
50
60
35
,
2
25
,115,00
VRESET (V)
IRESET (uA)
Figure 19-18 Reset Pull-up Resistor Current vs. Reset Pin Voltage (VCC = 5V)
RESET PULL-UP RESISTOR CURRENT vs. RESET PIN VOLTAGE
85 °C
25 °C
-40 °C
0
20
40
60
80
100
120
0 0,5 1 1,5 2 2,5 3 3,5 4 4,5 5
VRESET (V)
IRESET (uA)
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19.6. Pin Driver Strength
Figure 19-19 I/O Pin Output Voltage vs. Sink Current (VCC = 1.8V)
I/O P IN OUTPUT VOLTAGE vs. S INK CURRENT
VCC = 1.8V
85 °C
25 °C
-40 °C
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5
IOL (mA)
VOL (V)
Figure 19-20 I/O Pin Output Voltage vs. Sink Current (VCC = 3V)
I/O P IN OUTPUT VOLTAGE vs. S INK CURRENT
VCC = 3V
85 °C
25 °C
-40 °C
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
012345678910
IOL (mA)
VOL (V)
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Figure 19-21 I/O pin Output Voltage vs. Sink Current (VCC = 5V)
I/O P IN OUTPUT VOLTAGE vs. S INK CURRENT
VCC = 5V
85 °C
25 °C
-40 °C
0
0.2
0.4
0.6
0.8
1
0 2 4 6 8 10 12 14 16 18 20
IOL (mA)
VOL (V)
Figure 19-22 I/O Pin Output Voltage vs. Source Current (VCC = 1.8V)
I/O P IN OUTPUT VOLTAGE vs. S OURCE CURRENT
VCC = 1.8V
85 °C
25 °C
-40 °C
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
2
0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5
IOH (mA)
VOH (V)
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Figure 19-23 I/O Pin Output Voltage vs. Source Current (VCC = 3V)
I/O P IN OUTPUT VOLTAGE vs. S OURCE CURRENT
VCC = 3V
85 °C
25 °C
-40 °C
1.5
1.7
1.9
2.1
2.3
2.5
2.7
2.9
3.1
012345678910
IOH (mA)
VOH (V)
Figure 19-24 I/O Pin output Voltage vs. Source Current (VCC = 5V)
I/O P IN OUTP UT VOLTAGE vs . S OURCE CURRENT
VCC = 5V
85 °C
25 °C
-40 °C
4
4.2
4.4
4.6
4.8
5
5.2
0 2 4 6 8 10 12 14 16 18 20
IOH (mA)
VOH (V)
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Figure 19-25 Reset Pin as I/O, Output Voltage vs. Sink Current
OUTPUT VOLTAGE vs . S INK CURRENT
RES ET PIN AS I/O
5.0 V
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
43210
IOL (mA)
VOL (V)
3.0 V
1.8 V
Figure 19-26 Reset Pin as I/O, Output Voltage vs. Source Current
OUTPUT VOLTAGE vs. S OURCE CURRENT
RES ET P IN AS I/O
5.0 V
3.0 V
0
1
2
3
4
5
0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2
IOH (mA)
VOH (V)
1.8 V
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19.7. Pin Threshold and Hysteresis
Figure 19-27 I/O Pin Input Threshold Voltage vs. VCC (VIH, IO Pin Read as ‘1’)
I/O PIN INPUT THRESHOLD VOLTAGE vs. VCC
VIH, IO PIN READ AS '1'
85 °C
25 °C
-40 °C
0
0,5
1
1,5
2
2,5
3
3,5
1,5 2 2,5 3 3,5 4 4,5 5 5,5
VCC (V)
Threshold (V)
Figure 19-28 I/O Pin Input threshold Voltage vs. VCC (VIL, IO Pin Read as ‘0’)
I/O PIN INPUT THRESHOLD VOLTAGE vs. VCC
VIL, IO PIN READ AS '0'
85 °C
25 °C
-40 °C
0
0,5
1
1,5
2
2,5
3
1,5 2 2,5 3 3,5 4 4,5 5 5,5
VCC (V)
Threshold (V)
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Figure 19-29 I/O Pin Input Hysteresis vs. VCC
I/O PIN INPUT HYSTERESIS vs. VCC
85 °C
25 °C
-40 °C
0
0,1
0,2
0,3
0,4
0,5
0,6
0,7
0,8
0,9
1
1,5 2 2,5 3 3,5 4 4,5 5 5,5
VCC (V)
Input Hysteresis (V)
Figure 19-30 Reset Pin as I/O, Input Threshold Voltage vs. VCC (VIH, I/O Pin Read as ‘1’)
RESET PIN AS I/O THRESHOLD VOLTAGE vs. VCC
VIH, RESET READ AS '1'
85 °C
25 °C
-40 °C
0
0,5
1
1,5
2
2,5
3
1,5 2 2,5 3 3,5 4 4,5 5 5,5
VCC (V)
Threshold (V)
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Figure 19-31 Reset Pin as I/O, Input Threshold Voltage vs. VCC (VIL, I/O pin Read as ‘0’)
RESET PIN AS I/O THRESHOLD VOLTAGE vs. VCC
VIL, RESET READ AS '0'
85 °C
25 °C
-40 °C
0
0,5
1
1,5
2
2,5
1,5 2 2,5 3 3,5 4 4,5 5 5,5
VCC (V)
Threshold (V)
Figure 19-32 Reset Input Hysteresis vs. VCC (Reset Pin Used as I/O)
RESET PIN AS I/O, INPUT HYSTERESIS vs. VCC
VIL, PIN READ AS "0"
85 °C
25 °C
-40 °C
0
0,1
0,2
0,3
0,4
0,5
0,6
0,7
0,8
0,9
1
1,5 2 2,5 3 3,5 4 4,5 5 5,5
VCC (V)
Input Hysteresis (V)
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Figure 19-33 Reset Input Threshold Voltage vs. VCC (VIH, I/O Pin Read as ‘1’)
RESET INPUT THRESHOLD VOLTAGE vs. VCC
VIH, IO PIN READ AS '1'
85 °C
25 °C
-40 °C
0
0,5
1
1,5
2
2,5
1,5 2 2,5 3 3,5 4 4,5 5 5,5
VCC (V)
Threshold (V)
Figure 19-34 Reset Input Threshold Voltage vs. VCC (VIL, I/O pin Read as ‘0’)
RESET INPUT THRESHOLD VOLTAGE vs. VCC
VIL, IO PIN READ AS '0'
85 °C
25 °C
-40 °C
0
0,5
1
1,5
2
2,5
1,5 2 2,5 3 3,5 4 4,5 5 5,5
VCC (V)
Threshold (V)
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Figure 19-35 Reset Pin, Input Hysteresis vs. VCC
RESET PIN INPUT HYSTERESIS vs. VCC
85 °C
25 °C
-40 °C
0
0,2
0,4
0,6
0,8
1
1,5 2 2,5 3 3,5 4 4,5 5 5,5
VCC (V)
Input Hysteresis (V)
19.8. Analog Comparator Offset
Figure 19-36 Analog Comparator Offset
ANALOG COMPARATOR OFFS ET
VCC = 5V
85
25
-40
0
0.002
0.004
0.006
54321
0
VIN
Offs et
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19.9. Internal Oscillator Speed
Figure 19-37 Watchdog Oscillator Frequency vs. VCC
WATCHDOG OS CILLATOR FREQUENCY vs . OP ERATING VOLTAGE
85 °C
25 °C
-40 °C
99
100
101
102
103
104
105
106
107
108
109
110
1.5 2 2.5 3 3.5 4 4.5 5 5.5
VCC (V)
Fre que ncy (kHz)
Figure 19-38 Watchdog Oscillator Frequency vs. Temperature
WATCHDOG OS CILLATOR FREQUENCY vs . TEMP ERATURE
5.5 V
4.0 V
3.3 V
2.7 V
1.8 V
100
101
102
103
104
105
106
107
108
109
110
-60 -40 -20 0 20 40 60 80 100
Tempe ra ture
Fre que ncy (kHz)
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Figure 19-39 Calibrated Oscillator Frequency vs. VCC
CALIBRATED 8.0MHz OSCILLATOR FREQUENCY vs. OP ERATING VOLTAGE
85 °C
25 °C
-40 °C
7.4
7.6
7.8
8
8.2
8.4
1.5 2 2.5 3 3.5 4 4.5 5 5.5
VCC (V)
Fre que ncy (MHz)
Figure 19-40 Calibrated Oscillator Frequency vs. Temperature
CALIBRATED 8.0MHz OSCILLATOR FREQUENCY vs . TEMP ERATURE
5.0 V
3.0 V
1.8 V
7.6
7.7
7.8
7.9
8
8.1
8.2
8.3
-40 -20 0 20 40 60 80 100
Temperature
Fre quency (MHz)
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Figure 19-41 Calibrated Oscillator Frequency vs. OSCCAL Value
CALIBRATED 8.0MHz RC OS CILLATOR FREQUENCY vs. OSCCAL VALUE
VCC = 3V
85 °C
25 °C
-40 °C
0
2
4
6
8
10
12
14
16
0 16 32 48 64 80 96 112 128 144 160 176 192 208 224 240
OS CCAL (X1)
Fre quency (MHz)
19.10. VLM Thresholds
Figure 19-42 VLM1L Threshold of VCC Level Monitor
VLM THRES HOLD vs. TEMPERATURE
VLM2:0 = 001
1.34
1.35
1.36
1.37
1.38
1.39
1.4
1.41
1.42
-40 -20 0 20 40 60 80 100
Tempe ra ture (C)
Thre s hold (V)
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Figure 19-43 VLM1H Threshold of VCC Level Monitor
VLM THRESHOLD vs . TEMP ERATURE
VLM2:0 = 010
1.4
1.45
1.5
1.55
1.6
1.65
1.7
-40 -20 0 20 40 60 80 100
Tempera ture (C)
Thre s hold (V)
Figure 19-44 VLM2 Threshold of VCC Level Monitor
VLM THRESHOLD vs. TEMPERATURE
VLM2:0 = 011
2.43
2.44
2.45
2.46
2.47
2.48
-40 -20 0 20 40 60 80 100
Tempe ra ture (C)
Thre s hold (V)
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Figure 19-45 VLM3 Threshold of VCC Level Monitorr2
VLM THRESHOLD vs . TEMPERATURE
VLM2:0 = 100
3.4
3.5
3.6
3.7
3.8
3.9
-40 -20 0 20 40 60 80 100
Tempe ra ture (C)
Thre s hold (V)
19.11. Current Consumption of Peripheral Units
Figure 19-46 ADC Current vs. VCC (ATtiny5/10, only)
ADC CURRENT vs . VCC
4.0 MHz FREQUENCY
0
100
200
300
400
500
600
700
1.5 2 2.5 3 3.5 4 4.5 5 5.5
VCC (V)
ICC (uA)
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Figure 19-47 Analog Comparator Current vs. VCC
ANALOG COMP ARATOR CURRENT vs. VCC
0
20
40
60
80
100
120
140
1,5 2 2,5 3 3,5 4 4,5 5 5,5
V
CC (V)
I
CC (uA)
25 ˚C
Figure 19-48 VCC Level Monitor Current vs. VCC
VLM SUPP LY CURRENT vs . VCC
VLM2:0 = 100
VLM2:0 = 011
VLM2:0 = 010
VLM2:0 = 001
VLM2:0 = 000
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
1.5 2 2.5 3 3.5 4 4.5 5 5.5
VCC (V)
ICC (mA)
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Figure 19-49 Temperature Dependence of VLM Current vs. VCC
VLM SUP P LY CURRENT vs. VCC
VLM2:0 = 001
85 °C
25 °C
-40 °C
0
50
100
150
200
250
300
350
1.5 2 2.5 3 3.5 4 4.5 5 5.5
VCC (V)
ICC (uA)
Figure 19-50 Watchdog Timer Current vs. VCC
85 °C
25 °C
-40 °C
0
1
2
3
4
5
6
7
8
9
1,5 2 2,5 3 3,5 4 4,5 5 5,5
VCC (V)
ICC (uA)
WATCHDOG TIMER CURRENT vs. VCC
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19.12. Current Consumption in Reset and Reset Pulsewidth
Figure 19-51 Reset Supply Current vs. VCC (0.1 - 1.0 MHz, excluding Current Through the Reset Pull-up)
RESET SUPPLY CURRENT vs. VCC
EXCLUDING CURRENT THROUGH THE RESET PULLUP
5.5 V
5.0 V
4.5 V
4.0 V
3.3 V
2.7 V
1.8 V
0
0,1
0,2
0,3
0,4
0,5
0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8 0,9 1
Frequency (MHz)
ICC (mA)
Note: The default clock source for the device is always the internal 8 MHz oscillator. Hence, current
consumption in reset remains unaffected by external clock signals.
Figure 19-52 Minimum Reset Pulse Width vs. VCC
MINIMUM RESET PULSE WIDTH vs. VCC
85 °C
25 °C
-40 °C
0
500
1000
1500
2000
2500
1,5 2 2,5 3 3,5 4 4,5 5 5,5
VCC (V)
Pulsewidth (ns)
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20. Register Summary
Offset Name Bit Pos.
0x00 PINB 7:0 PINB3 PINB2 PINB1 PINB0
0x01 DDRB 7:0 DDRB3 DDRB2 DDRB1 DDRB0
0x02 PORTB 7:0 PORTB3 PORTB2 PORTB1 PORTB0
0x03 PUEB 7:0 PUEB3 PUEB2 PUEB1 PUEB0
0x04
...
0x0B
Reserved
0x0C PORTCR 7:0 BBMB
0x0D
...
0x0F
Reserved
0x10 PCMSK 7:0 PCINT3 PCINT2 PCINT1 PCINT0
0x11 PCIFR 7:0 PCIF0
0x12 PCICR 7:0 PCIE0
0x13 EIMSK 7:0 INT0
0x14 EIFR 7:0 INTF0
0x15 EICRA 7:0 ISC0[1:0]
0x16 Reserved
0x17 DIDR0 7:0 ADC3D ADC2D ADC1D ADC0D
0x18 Reserved
0x19 ADCL 7:0 ADC7 ADC6 ADC5 ADC4 ADC3 ADC2 ADC1 ADC0
0x1A Reserved
0x1B ADMUX 7:0 MUX1 MUX0
0x1C ADCSRB 7:0 ADTS2 ADTS1 ADTS0
0x1D ADCSRA 7:0 ADEN ADSC ADATE ADIF ADIE ADPS2 ADPS1 ADPS0
0x1E Reserved
0x1F ACSR 7:0 ACD ACO ACI ACIE ACIC ACIS1 ACIS0
0x20
...
0x21
Reserved
0x22 ICR0L 7:0 (ICR0[7:0]) ICR0L[7:0]
0x23 ICR0H 7:0 (ICR0[15:8]) ICR0H[7:0]
0x24 OCR0BL 7:0 (OCR0B[7:0]) OCR0BL[7:0]
0x25 OCR0BH 7:0 (OCR0B[15:8]) OCR0BH[7:0]
0x26 OCR0AL 7:0 (OCR0A[7:0]) OCR0AL[7:0]
0x27 OCR0AH 7:0 (OCR0A[15:8]) OCR0AH[7:0]
0x28 TCNT0L 7:0 (TCNT0[7:0]) TCNT0L[7:0]
0x29 TCNT0H 7:0 (TCNT0[15:8]) TCNT0H[7:0]
0x2A TIFR0 7:0 ICF0 OCF0B OCF0A TOV0
0x2B TIMSK0 7:0 ICIE0 OCIE0B OCIE0A TOIE0
0x2C TCCR0C 7:0 FOC0A FOC0B
0x2D TCCR0B 7:0 ICNC0 ICES0 WGM03 WGM02 CS0[2:0]
0x2E TCCR0A 7:0 COM0A1 COM0A0 COM0B1 COM0B0 WGM01 WGM00
0x2F GTCCR 7:0 TSM PSR
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Offset Name Bit Pos.
0x30 Reserved
0x31 WDTCSR 7:0 WDIF WDIE WDP3 WDE WDP2 WDP1 WDP0
0x32 NVMCSR 7:0 NVMBSY
0x33 NVMCMD 7:0 NVMCMD[5:0]
0x34 VLMCSR 7:0 VLMF VLMIE VLM[2:0]
0x35 PRR 7:0 PRADC PRTIM0
0x36 CLKPSR 7:0 CLKPS[3:0]
0x37 CLKMSR 7:0 CLKMS[1:0]
0x38 Reserved
0x39 OSCCAL 7:0 CAL[7:0]
0x3A SMCR 7:0 SM[2:0] SE
0x3B RSTFLR 7:0 WDRF EXTRF PORF
0x3C CCP 7:0 CCP[7:0]
0x3D SPL 7:0 (SP[7:0]) SPL[7:0]
0x3E SPH 7:0 (SP[15:8]) SPH[7:0]
0x3F SREG 7:0 I T H S V N Z C
20.1. Note
1. For compatibility with future devices, reserved bits should be written to zero if accessed. Reserved
I/O memory addresses should never be written.
2. I/O Registers within the address range 0x00 - 0x1F are directly bit-accessible using the SBI and
CBI instructions. In these registers, the value of single bits can be checked by using the SBIS and
SBIC instructions.
3. Some of the Status Flags are cleared by writing a logical one to them. Note that, unlike most other
AVRs, the CBI and SBI instructions will only operation the specified bit, and can therefore be used
on registers containing such Status Flags. The CBI and SBI instructions work with registers 0x00 to
0x1F only.
4. The ADC is available in ATtiny5/10, only.
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21. Instruction Set Summary
ARITHMETIC AND LOGIC INSTRUCTIONS
Mnemonics Operands Description Operation Flags #Clocks
ADD Rd, Rr Add two Registers without Carry Rd ← Rd + Rr Z,C,N,V,S,H 1
ADC Rd, Rr Add two Registers with Carry Rd ← Rd + Rr + C Z,C,N,V,S,H 1
SUB Rd, Rr Subtract two Registers Rd ← Rd - Rr Z,C,N,V,S,H 1
SUBI Rd, K Subtract Constant from Register Rd ← Rd - K Z,C,N,V,S,H 1
SBC Rd, Rr Subtract two Registers with Carry Rd ← Rd - Rr - C Z,C,N,V,S,H 1
SBCI Rd, K Subtract Constant from Reg with Carry. Rd ← Rd - K - C Z,C,N,V,S,H 1
AND Rd, Rr Logical AND Registers Rd ← Rd · Rr Z,N,V,S 1
ANDI Rd, K Logical AND Register and Constant Rd ← Rd · K Z,N,V,S 1
OR Rd, Rr Logical OR Registers Rd ← Rd v Rr Z,N,V,S 1
ORI Rd, K Logical OR Register and Constant Rd ← Rd v K Z,N,V,S 1
EOR Rd, Rr Exclusive OR Registers Rd ← Rd ⊕ Rr Z,N,V,S 1
COM Rd One’s Complement Rd ← 0xFF - Rd Z,C,N,V,S 1
NEG Rd Two’s Complement Rd ← 0x00 - Rd Z,C,N,V,S,H 1
SBR Rd,K Set Bit(s) in Register Rd ← Rd v K Z,N,V,S 1
CBR Rd,K Clear Bit(s) in Register Rd ← Rd · (0xFF - K) Z,N,V,S 1
INC Rd Increment Rd ← Rd + 1 Z,N,V,S 1
DEC Rd Decrement Rd ← Rd - 1 Z,N,V,S 1
TST Rd Test for Zero or Minus Rd ← Rd · Rd Z,N,V,S 1
CLR Rd Clear Register Rd ← Rd ⊕ Rd Z,N,V,S 1
SER Rd Set Register Rd ← 0xFF None 1
BRANCH INSTRUCTIONS
Mnemonics Operands Description Operation Flags #Clocks
RJMP k Relative Jump PC ← PC + k + 1 None 2
IJMP Indirect Jump to (Z) PC(15:0) ← Z, PC(21:16) ← 0 None 2
RCALL k Relative Subroutine Call PC ← PC + k + 1 None 3/4
ICALL Indirect Call to (Z) PC(15:0) ← Z, PC(21:16) ← 0 None 3/4
RET Subroutine Return PC ← STACK None 4/5
RETI Interrupt Return PC ← STACK I 4/5
CPSE Rd,Rr Compare, Skip if Equal if (Rd = Rr) PC ← PC + 2 or 3 None 1/2/3
CP Rd,Rr Compare Rd - Rr Z, N,V,C,S,H 1
CPC Rd,Rr Compare with Carry Rd - Rr - C Z, N,V,C,S,H 1
CPI Rd,K Compare Register with Immediate Rd - K Z, N,V,C,S,H 1
SBRC Rr, b Skip if Bit in Register Cleared if (Rr(b)=0) PC ← PC + 2 or 3 None 1/2/3
SBRS Rr, b Skip if Bit in Register is Set if (Rr(b)=1) PC ← PC + 2 or 3 None 1/2/3
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BRANCH INSTRUCTIONS
Mnemonics Operands Description Operation Flags #Clocks
SBIC A, b Skip if Bit in I/O Register Cleared if (I/O(A,b)=1) PC ← PC + 2 or 3 None 1/2/3
SBIS A, b Skip if Bit in I/O Register is Set if (I/O(A,b)=1) PC ← PC + 2 or 3 None 1/2/3
BRBS s, k Branch if Status Flag Set if (SREG(s) = 1) then PC←PC+k + 1 None 1/2
BRBC s, k Branch if Status Flag Cleared if (SREG(s) = 0) then PC←PC+k + 1 None 1/2
BREQ k Branch if Equal if (Z = 1) then PC ← PC + k + 1 None 1/2
BRNE k Branch if Not Equal if (Z = 0) then PC ← PC + k + 1 None 1/2
BRCS k Branch if Carry Set if (C = 1) then PC ← PC + k + 1 None 1/2
BRCC k Branch if Carry Cleared if (C = 0) then PC ← PC + k + 1 None 1/2
BRSH k Branch if Same or Higher if (C = 0) then PC ← PC + k + 1 None 1/2
BRLO k Branch if Lower if (C = 1) then PC ← PC + k + 1 None 1/2
BRMI k Branch if Minus if (N = 1) then PC ← PC + k + 1 None 1/2
BRPL k Branch if Plus if (N = 0) then PC ← PC + k + 1 None 1/2
BRGE k Branch if Greater or Equal, Signed if (N ⊕ V= 0) then PC ← PC + k + 1 None 1/2
BRLT k Branch if Less Than Zero, Signed if (N ⊕ V= 1) then PC ← PC + k + 1 None 1/2
BRHS k Branch if Half Carry Flag Set if (H = 1) then PC ← PC + k + 1 None 1/2
BRHC k Branch if Half Carry Flag Cleared if (H = 0) then PC ← PC + k + 1 None 1/2
BRTS k Branch if T Flag Set if (T = 1) then PC ← PC + k + 1 None 1/2
BRTC k Branch if T Flag Cleared if (T = 0) then PC ← PC + k + 1 None 1/2
BRVS k Branch if Overflow Flag is Set if (V = 1) then PC ← PC + k + 1 None 1/2
BRVC k Branch if Overflow Flag is Cleared if (V = 0) then PC ← PC + k + 1 None 1/2
BRIE k Branch if Interrupt Enabled if ( I = 1) then PC ← PC + k + 1 None 1/2
BRID k Branch if Interrupt Disabled if ( I = 0) then PC ← PC + k + 1 None 1/2
BIT AND BIT-TEST INSTRUCTIONS
Mnemonics Operands Description Operation Flags #Clocks
LSL Rd Logical Shift Left Rd(n+1) ← Rd(n), Rd(0) ← 0 Z,C,N,V,H 1
LSR Rd Logical Shift Right Rd(n) ← Rd(n+1), Rd(7) ← 0 Z,C,N,V 1
ROL Rd Rotate Left Through Carry Rd(0)←C,Rd(n+1)← Rd(n),C¬Rd(7) Z,C,N,V,S 1
ROR Rd Rotate Right Through Carry Rd(7)←C,Rd(n)← Rd(n+1),C←Rd(0) Z,C,N,V 1
ASR Rd Arithmetic Shift Right Rd(n) ← Rd(n+1), n=0...6 Z,C,N,V 1
SWAP Rd Swap Nibbles Rd(3...0)←Rd(7...4),Rd(7...4)¬Rd(3...0) None 1
BSET s Flag Set SREG(s) ← 1 SREG(s) 1
BCLR s Flag Clear SREG(s) ← 0 SREG(s) 1
SBI A, b Set Bit in I/O Register I/O(A, b) ← 1 None 1
CBI A, b Clear Bit in I/O Register I/O(A, b) ← 0 None 1
BST Rr, b Bit Store from Register to T T ← Rr(b) T 1
BLD Rd, b Bit load from T to Register Rd(b) ← T None 1
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BIT AND BIT-TEST INSTRUCTIONS
Mnemonics Operands Description Operation Flags #Clocks
SEC Set Carry C ← 1 C 1
CLC Clear Carry C ← 0 C 1
SEN Set Negative Flag N ← 1 N 1
CLN Clear Negative Flag N ← 0 N 1
SEZ Set Zero Flag Z ← 1 Z 1
CLZ Clear Zero Flag Z ← 0 Z 1
SEI Global Interrupt Enable I ← 1 I 1
CLI Global Interrupt Disable I ← 0 I 1
SES Set Signed Test Flag S ← 1 S 1
CLS Clear Signed Test Flag S ← 0 S 1
SEV Set Two’s Complement Overflow. V ← 1 V 1
CLV Clear Two’s Complement Overflow V ← 0 V 1
SET Set T in SREG T ← 1 T 1
CLT Clear T in SREG T ← 0 T 1
SEH Set Half Carry Flag in SREG H ← 1 H 1
CLH Clear Half Carry Flag in SREG H ← 0 H 1
DATA TRANSFER INSTRUCTIONS
Mnemonics Operands Description Operation Flags #Clocks
MOV Rd, Rr Move Between Registers Rd ← Rr None 1
LDI Rd, K Load Immediate Rd ← K None 1
LD Rd, X Load Indirect Rd ← (X) None 1/2
LD Rd, X+ Load Indirect and Post-Increment Rd ← (X), X ← X + 1 None 2
LD Rd, - X Load Indirect and Pre-Decrement X ← X - 1, Rd ← (X) None 2
LD Rd, Y Load Indirect Rd ← (Y) None 2
LD Rd, Y+ Load Indirect and Post-Increment Rd ← (Y), Y ← Y + 1 None 2
LD Rd, - Y Load Indirect and Pre-Decrement Y ← Y - 1, Rd ← (Y) None 2
LD Rd, Z Load Indirect Rd ← (Z) None 2
LD Rd, Z+ Load Indirect and Post-Increment Rd ← (Z), Z ← Z+1 None 2
LD Rd, -Z Load Indirect and Pre-Decrement Z ← Z - 1, Rd ← (Z) None 2
LDS Rd, k Load Direct from SRAM Rd ← (k) None 2
ST X, Rr Store Indirect (X) ← Rr None 2
ST X+, Rr Store Indirect and Post-Increment (X) ← Rr, X ← X + 1 None 2
ST - X, Rr Store Indirect and Pre-Decrement X ← X - 1, (X) ← Rr None 2
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DATA TRANSFER INSTRUCTIONS
Mnemonics Operands Description Operation Flags #Clocks
ST Y, Rr Store Indirect (Y) ← Rr None 2
ST Y+, Rr Store Indirect and Post-Increment (Y) ← Rr, Y ← Y + 1 None 2
ST - Y, Rr Store Indirect and Pre-Decrement Y ← Y - 1, (Y) ← Rr None 2
ST Z, Rr Store Indirect (Z) ← Rr None 2
ST Z+, Rr Store Indirect and Post-Increment (Z) ← Rr, Z ← Z + 1 None 2
ST -Z, Rr Store Indirect and Pre-Decrement Z ← Z - 1, (Z) ← Rr None 2
STS k, Rr Store Direct to SRAM (k) ← Rr None 2
IN Rd, A In from I/O Location Rd ← I/O (A) None 1
OUT A, Rr Out to I/O Location I/O (A) ← Rr None 1
PUSH Rr Push Register on Stack STACK ← Rr None 2
POP Rd Pop Register from Stack Rd ← STACK None 2
MCU CONTROL INSTRUCTIONS
Mnemonics Operands Description Operation Flags #Clocks
NOP No Operation No Operation None 1
SLEEP Sleep (see specific descr. for Sleep function) None 1
WDR Watchdog Reset (see specific descr. for WDR/timer) None 1
BREAK Break For On-chip Debug Only None N/A
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22. Packaging Information
22.1. 6ST1
Figure 21-1 6ST1
TITLE DRAWING NO. GPC REV.
Packag e Drawing Contac t:
pa cka ge drawings @ a tme l.com 6S T1TAQ A
6S T1, 6-lead, 2.90 x 1.60 mm Plastic Small Outline
Package (SOT23)
MAX NOTE
SYMBOL MIN NOM
COMMON DIMENSIONS
(Unit of Me a sure = mm)
A – – 1.45
A1 0 – 0.15
A2 0.90 – 1.30
D 2.80 2.90 3.00 2
E 2.60 2.80 3.00
E1 1.50 1.60 1.75
L 0.30 0.45 0.55
e 0.95 BS C
b 0.30 – 0.50 3
c 0.09 – 0.20
θ 0° – 8°
Notes: 1. This package is compliant with JEDEC specif cation MO-178 Variation AB
2. Dimension D does not include mold Flash, protrusions or gate burrs.
Mold Flash, protrustion or gate burrs shall not exceed 0.25 mm per end.
3. Dimension b does not include dambar protrusion. Allowable dambar
protrusion shall not cause the lead width to exceed the maximum
b dimension by more than 0.08 mm
4. Die is facing down after trim/form.
6/30/08
Side View
E E1
D
e
A2 A
A1 C
C
0.10
0.25
L
O
A2 A
A1 C
C
0.10
A
A
SEE VIEW B
C
SEATING PLANE
SEATING PLANE
SEATING PLANE
c
b
Pin #1 ID
1
6
23
54
To p View
View B
View A-A
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22.2. 8MA4
Figure 21-2 8MA4
TITLE DRAWING NO.GPC REV.
Packag e Drawing Contac t:
pa cka ge drawings @ a tme l.com 8MA4YAG A
8PAD, 2x2x0.6 mm bo dy, 0.5 mm pitch,
0.9x1.5 mm expo s e d pad, S aw s ingulated
The rmally e nhanc ed plas tic ultra thin dual flat
no lead packag e (UDFN/USON)
12/17/09
COMMON DIMENSIONS
(Unit of Me a s ure = mm)
SYMBOL MIN NOM MAX NOTE
A – – 0.60
A1 0.00 – 0.05
b 0.20 – 0.30
D 1.95 2.00 2.05
D2 1.40 1.50 1.60
E 1.95 2.00 2.05
E2 0.80 0.90 1.00
e – 0.50 –
L 0.20 0.30 0.40
K 0.20 – –
TOP VIEW
BOTTOM VIEW
Note : 1. ALL DIMENSIONS ARE IN mm. ANGLES IN DEGREES.
2. C OPLANARITY APPLIES TO THE EXPOSED PAD AS WELL AS THE
TERMINALS COPLANARITY SHALL NOT EXCEED 0.05 mm.
3. WARPAGE SHALL NOT EXCEED 0.05 mm.
4. REFER JEDEC MO-236/MO-252
Pin 1 ID
E
D
D2
1 2 3 4
8 7 6 5
E2
b
14
8
5
e
K
L
0.05
SIDE VIEW
A1
A
c
c
0.05 c
8x
C0.2
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23. Errata
23.1. ATtiny4
23.1.1. Rev. E
• Programming Lock Bits
1. Programming Lock Bits
Programming Lock Bits to a lock mode equal or lower than the current causes one word of Flash to be
corrupted. The location of the corruption is random.
Problem Fix / Workaround
When programming Lock Bits, make sure lock mode is not set to present, or lower levels.
23.1.2. Rev. D
• ESD HBM (ESD STM 5.1) level ±1000V
• Programming Lock Bits
1. ESD HBM (ESD STM 5.1) level ±1000V
The device meets ESD HBM (ESD STM 5.1) level ±1000V.
Problem Fix / Workaround
Always use proper ESD protection measures (Class 1C) when handling integrated circuits before and
during assembly.
2. Programming Lock Bits
Programming Lock Bits to a lock mode equal or lower than the current causes one word of Flash to be
corrupted. The location of the corruption is random.
Problem Fix / Workaround
When programming Lock Bits, make sure lock mode is not set to present, or lower levels.
23.1.3. Rev. A – C
Not sampled.
23.2. ATtiny5
23.2.1. Rev. E
• Programming Lock Bits
1. Programming Lock Bits
Programming Lock Bits to a lock mode equal or lower than the current causes one word of Flash to be
corrupted. The location of the corruption is random.
Problem Fix / Workaround
When programming Lock Bits, make sure lock mode is not set to present, or lower levels.
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23.2.2. Rev. D
• ESD HBM (ESD STM 5.1) level ±1000V
• Programming Lock Bits
1. ESD HBM (ESD STM 5.1) level ±1000V
The device meets ESD HBM (ESD STM 5.1) level ±1000V.
Problem Fix / Workaround
Always use proper ESD protection measures (Class 1C) when handling integrated circuits before and
during assembly.
2. Programming Lock Bits
Programming Lock Bits to a lock mode equal or lower than the current causes one word of Flash to be
corrupted. The location of the corruption is random.
Problem Fix / Workaround
When programming Lock Bits, make sure lock mode is not set to present, or lower levels.
23.2.3. Rev. A – C
Not sampled.
23.3. ATtiny9
23.3.1. Rev. E
• Programming Lock Bits
1. Programming Lock Bits
Programming Lock Bits to a lock mode equal or lower than the current causes one word of Flash to be
corrupted. The location of the corruption is random.
Problem Fix / Workaround
When programming Lock Bits, make sure lock mode is not set to present, or lower levels.
23.3.2. Rev. D
• ESD HBM (ESD STM 5.1) level ±1000V
• Programming Lock Bits
1. ESD HBM (ESD STM 5.1) level ±1000V
The device meets ESD HBM (ESD STM 5.1) level ±1000V.
Problem Fix / Workaround
Always use proper ESD protection measures (Class 1C) when handling integrated circuits before and
during assembly.
2. Programming Lock Bits
Programming Lock Bits to a lock mode equal or lower than the current causes one word of Flash to be
corrupted. The location of the corruption is random.
Problem Fix / Workaround
When programming Lock Bits, make sure lock mode is not set to present, or lower levels.
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23.3.3. Rev. A – C
Not sampled.
23.4. ATtiny10
23.4.1. Rev. E
• Programming Lock Bits
1. Programming Lock Bits
Programming Lock Bits to a lock mode equal or lower than the current causes one word of Flash to be
corrupted. The location of the corruption is random.
Problem Fix / Workaround
When programming Lock Bits, make sure lock mode is not set to present, or lower levels.
23.4.2. Rev. C – D
• ESD HBM (ESD STM 5.1) level ±1000V
• Programming Lock Bits
1. ESD HBM (ESD STM 5.1) level ±1000V
The device meets ESD HBM (ESD STM 5.1) level ±1000V.
Problem Fix / Workaround
Always use proper ESD protection measures (Class 1C) when handling integrated circuits before and
during assembly.
2. Programming Lock Bits
Programming Lock Bits to a lock mode equal or lower than the current causes one word of Flash to be
corrupted. The location of the corruption is random.
Problem Fix / Workaround
When programming Lock Bits, make sure lock mode is not set to present, or lower levels.
23.4.3. Rev. A – B
Not sampled.
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24. Datasheet Revision History
24.1. Rev. 8127F – 02/13
1. Updated:
–Ordering Information on page 9
24.2. Rev. 8127E – 11/11
1. Updated:
–Device status from Preliminary to Final
–Ordering Information on page 9
24.3. Rev. 8127D – 02/10
1. Added UDFN package in Feature on page 1, Pin Configurations on page 7, Ordering Information
on page 9, and in Packaging Information on page 202
2. Updated Figures in Section Power-on Reset on page 47
3. Updated Section External Reset on page 48
4. Updated Figure 19-36 Analog Comparator Offset on page 187 and Figure 19-51 Reset Supply
Current vs. VCC (0.1 - 1.0 MHz, excluding Current Through the Reset Pull-up) on page 195 in
“Typical Characteristics”
5. Updated notes in Section Ordering Information on page 9
6. Added device Rev. E in Section Errata on page 204
24.4. Rev. 8127C – 10/09
1. Updated values and notes:
–Table 18-1 DC Characteristics. TA = -40°C to +85°C on page 162 in Section “DC
Characteristics”
–Table 18-3 External Clock Drive Characteristics on page 165 in Section “Clock
Characteristics”
–Table 18-6 Voltage Level Monitor Thresholds on page 166 in Section “VCC Level Monitor”
–Serial Programming Characteristics on page 167 in Section “Serial Programming
Characteristics”
2. Updated Figure 18-1 Maximum Frequency vs. VCC on page 164 in Section “Speed”
3. Added Typical Characteristics Figure 19-36 Analog Comparator Offset on page 187 in Section
“Analog Comparator Offset”. Also, updated some other plots in Typical Characteristics.
4. Added topside and bottomside marking notes in Section Ordering Information on page 9
5. Added ESD errata, see Section Errata on page 204
6. Added Lock bits re-programming errata, see Section Errata on page 204
24.5. Rev. 8127B – 08/09
1. Updated document template
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2. Expanded document to also cover devices ATtiny4, ATtiny5 and ATtiny9
3. Added section:
–Comparison of ATtiny4, ATtiny5, ATtiny9 and ATtiny10 on page 13
4. Updated sections:
–ADC Clock – clkADC on page 32
–Starting from Idle / ADC Noise Reduction / Standby Mode on page 35
–ADC Noise Reduction Mode on page 41
–Analog to Digital Converter on page 42
–SMCR on page 44
–PRR on page 45
–Alternate Functions of Port B on page 72
–Overview on page 124
–Physical Layer of Tiny Programming Interface on page 141
–Overview on page 152
–ADC Characteristics (ATtiny5/10, only) on page 167
–Supply Current of I/O Modules on page 169
–Register Summary
–Ordering Information on page 9
5. Added figure:
–Figure 16-2 Using an External Programmer for In-System Programming via TPI on page 141
6. Updated figure:
–Figure 6-1 Data Memory Map (Byte Addressing) on page 26
7. Added table:
–Table 17-4 Number of Words and Pages in the Flash (ATtiny4/5) on page 154
8. Updated tables:
–Table 9-1 Active Clock Domains and Wake-up Sources in the Different Sleep Modes. on page
40
–Table 11-1 Reset and Interrupt Vectors on page 56
–Table 17-3 Number of Words and Pages in the Flash (ATtiny9/10) on page 154
–Table 17-8 Signature codes on page 155
24.6. Rev. 8127A – 04/09
1. Initial revision
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