8-bit AVR - Atmel Corporation

Instruction Set Nomenclature

Status Register (SREG)

SREG: Status Register

C: Carry Flag

Z: Zero Flag

N: Negative Flag

V: Two’s complement overflow indicator

S: N ⊕ V, For signed tests

H: Half Carry Flag

T: Transfer bit used by BLD and BST instructions

I: Global Interrupt Enable/Disable Flag

Registers and Operands

Rd: Destination (and source) register in the Register File

Rr: Source register in the Register File

R: Result after instruction is executed

K: Constant data

k: Constant address

b: Bit in the Register File or I/O Register (3-bit)

s: Bit in the Status Register (3-bit)

X,Y,Z: Indirect Address Register

(X=R27:R26, Y=R29:R28 and Z=R31:R30)

A: I/O location address

q: Displacement for direct addressing (6-bit)

8-bit

Instruction Set

Rev. 0856E–AVR–11/05

2AVR Instruction Set

0856E–AVR–11/05

I/O Registers

RAMPX, RAMPY, RAMPZ

Registers concatenated with the X-, Y-, and Z-registers enabling indirect addressing of the whole data space on MCUs with

more than 64K bytes data space, and constant data fetch on MCUs with more than 64K bytes program space.

RAMPD

bytes data space.

EIND

than 64K words (128K bytes) program space.

Stack

STACK: Stack for return address and pushed registers

SP: Stack Pointer to STACK

Flags

⇔: Flag affected by instruction

0: Flag cleared by instruction

1: Flag set by instruction

-: Flag not affected by instruction

AVR Instruction Set

0856E–AVR–11/05

The Program and Data Addressing Modes

The AVR Enhanced RISC microcontroller supports powerful and efficient addressing modes for access to the Program

memory (Flash) and Data memory (SRAM, Register file, I/O Memory, and Extended I/O Memory). This section describes

the various addressing modes supported by the AVR architecture. In the following figures, OP means the operation code

part of the instruction word. To simplify, not all figures show the exact location of the addressing bits. To generalize, the

abstract terms RAMEND and FLASHEND have been used to represent the highest location in data and program space,

respectively.

Note: Not all addressing modes are present in all devices. Refer to the device spesific instruction summary.

Figure 1. Direct Single Register Addressing

The operand is contained in register d (Rd).

Figure 2. Direct Register Addressing, Two Registers

Operands are contained in register r (Rr) and d (Rd). The result is stored in register d (Rd).

4AVR Instruction Set

0856E–AVR–11/05

I/O Direct

Figure 3. I/O Direct Addressing

Operand address is contained in 6 bits of the instruction word. n is the destination or source register address.

Note: Some complex AVR Microcontrollers have more peripheral units than can be supported within the 64 locations reserved in the

opcode for I/O direct addressing. The extended I/O memory from address 64 to 255 can only be reached by data addressing,

not I/O addressing.

Data Direct

Figure 4. Direct Data Addressing

A 16-bit Data Address is contained in the 16 LSBs of a two-word instruction. Rd/Rr specify the destination or source

OP Rr/Rd

15 0

Data Address

0x0000

RAMEND

20 19

Data Space

AVR Instruction Set

0856E–AVR–11/05

Data Indirect with Displacement

Figure 5. Data Indirect with Displacement

Operand address is the result of the Y- or Z-register contents added to the address contained in 6 bits of the instruction

word. Rd/Rr specify the destination or source register.

Data Indirect

Figure 6. Data Indirect Addressing

Operand address is the contents of the X-, Y-, or the Z-register. In AVR devices without SRAM, Data Indirect Addressing is

called Register Indirect Addressing. Register Indirect Addressing is a subset of Data Indirect Addressing since the data

space form 0 to 31 is the Register File.

Data Space

0x0000

RAMEND

Y OR Z - REGISTER

OP qRr/Rd

05610

Data Space

0x0000

X, Y OR Z - REGISTER

015

RAMEND

6AVR Instruction Set

0856E–AVR–11/05

Data Indirect with Pre-decrement

Figure 7. Data Indirect Addressing with Pre-decrement

The X,- Y-, or the Z-register is decremented before the operation. Operand address is the decremented contents of the X-,

Y-, or the Z-register.

Data Indirect with Post-increment

Figure 8. Data Indirect Addressing with Post-increment

The X-, Y-, or the Z-register is incremented after the operation. Operand address is the content of the X-, Y-, or the Z-regis-

ter prior to incrementing.

Data Space

0x0000

X, Y OR Z - REGISTER

015

-1

RAMEND

Data Space

0x0000

X, Y OR Z - REGISTER

015

RAMEND

AVR Instruction Set

0856E–AVR–11/05

Program Memory Constant Addressing using the LPM, ELPM, and SPM Instructions

Figure 9. Program Memory Constant Addressing

Constant byte address is specified by the Z-register contents. The 15 MSBs select word address. For LPM, the LSB selects

low byte if cleared (LSB = 0) or high byte if set (LSB = 1). For SPM, the LSB should be cleared. If ELPM is used, the

RAMPZ Register is used to extend the Z-register.

Program Memory with Post-increment using the LPM Z+ and ELPM Z+ Instruction

Figure 10. Program Memory Addressing with Post-increment

Constant byte address is specified by the Z-register contents. The 15 MSBs select word address. The LSB selects low byte

if cleared (LSB = 0) or high byte if set (LSB = 1). If ELPM Z+ is used, the RAMPZ Register is used to extend the Z-register.

FLASHEND

0x0000

LSB

FLASHEND

0x0000

LSB

8AVR Instruction Set

0856E–AVR–11/05

Direct Program Addressing, JMP and CALL

Figure 11. Direct Program Memory Addressing

Program execution continues at the address immediate in the instruction word.

Indirect Program Addressing, IJMP and ICALL

Figure 12. Indirect Program Memory Addressing

Program execution continues at address contained by the Z-register (i.e., the PC is loaded with the contents of the Z-

FLASHEND

31 16

OP 6 MSB

16 LSB

21 0

15 0

0x0000

FLASHEND

15 0

0x0000

AVR Instruction Set

0856E–AVR–11/05

Relative Program Addressing, RJMP and RCALL

Figure 13. Relative Program Memory Addressing

Program execution continues at address PC + k + 1. The relative address k is from -2048 to 2047.

FLASHEND

0x0000

10 AVR Instruction Set

0856E–AVR–11/05

Conditional Branch Summary

Note: 1. Interchange Rd and Rr in the operation before the test, i.e., CP Rd,Rr → CP Rr,Rd

Test Boolean Mnemonic Complementary Boolean Mnemonic Comment

Rd > Rr Z•(N ⊕ V) = 0 BRLT(1) Rd ≤ Rr Z+(N ⊕ V) = 1 BRGE* Signed

Rd ≥ Rr (N ⊕ V) = 0 BRGE Rd < Rr (N ⊕ V) = 1 BRLT Signed

Rd = Rr Z = 1 BREQ Rd ≠ Rr Z = 0 BRNE Signed

Rd ≤ Rr Z+(N ⊕ V) = 1 BRGE(1) Rd > Rr Z•(N ⊕ V) = 0 BRLT* Signed

Rd < Rr (N ⊕ V) = 1 BRLT Rd ≥ Rr (N ⊕ V) = 0 BRGE Signed

Rd > Rr C + Z = 0 BRLO(1) Rd ≤ Rr C + Z = 1 BRSH* Unsigned

Rd ≥ Rr C = 0 BRSH/BRCC Rd < Rr C = 1 BRLO/BRCS Unsigned

Rd = Rr Z = 1 BREQ Rd ≠ Rr Z = 0 BRNE Unsigned

Rd ≤ Rr C + Z = 1 BRSH(1) Rd > Rr C + Z = 0 BRLO* Unsigned

Rd < Rr C = 1 BRLO/BRCS Rd ≥ Rr C = 0 BRSH/BRCC Unsigned

Carry C = 1 BRCS No carry C = 0 BRCC Simple

Negative N = 1 BRMI Positive N = 0 BRPL Simple

Overflow V = 1 BRVS No overflow V = 0 BRVC Simple

Zero Z = 1 BREQ Not zero Z = 0 BRNE Simple

AVR Instruction Set

0856E–AVR–11/05

Complete Instruction Set Summary

Instruction Set Summary

Mnemonics Operands Description Operation Flags

#Clock

Note

Arithmetic and Logic Instructions

ADD Rd, Rr Add without Carry Rd ← Rd + Rr Z,C,N,V,S,H 1

ADC Rd, Rr Add with Carry Rd ← Rd + Rr + C Z,C,N,V,S,H 1

ADIW Rd, K Add Immediate to Word Rd+1:Rd ← Rd+1:Rd + K Z,C,N,V,S 2 (1)

SUB Rd, Rr Subtract without Carry Rd ← Rd - Rr Z,C,N,V,S,H 1

SUBI Rd, K Subtract Immediate Rd ← Rd - K Z,C,N,V,S,H 1

SBC Rd, Rr Subtract with Carry Rd ← Rd - Rr - C Z,C,N,V,S,H 1

SBCI Rd, K Subtract Immediate with Carry Rd ← Rd - K - C Z,C,N,V,S,H 1

SBIW Rd, K Subtract Immediate from Word Rd+1:Rd ← Rd+1:Rd - K Z,C,N,V,S 2 (1)

AND Rd, Rr Logical AND Rd ← Rd • Rr Z,N,V,S 1

ANDI Rd, K Logical AND with Immediate Rd ← Rd • K Z,N,V,S 1

OR Rd, Rr Logical OR Rd ← Rd v Rr Z,N,V,S 1

ORI Rd, K Logical OR with Immediate Rd ← Rd v K Z,N,V,S 1

EOR Rd, Rr Exclusive OR Rd ← Rd ⊕ Rr Z,N,V,S 1

COM Rd One’s Complement Rd ← $FF - Rd Z,C,N,V,S 1

NEG Rd Two’s Complement Rd ← $00 - 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 • ($FFh - 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 ← $FF None 1

MUL Rd,Rr Multiply Unsigned R1:R0 ← Rd × Rr (UU) Z,C 2 (1)

MULS Rd,Rr Multiply Signed R1:R0 ← Rd × Rr (SS) Z,C 2 (1)

MULSU Rd,Rr Multiply Signed with Unsigned R1:R0 ← Rd × Rr (SU) Z,C 2 (1)

FMUL Rd,Rr Fractional Multiply Unsigned R1:R0 ← (Rd × Rr)<<1 (UU) Z,C 2 (1)

FMULS Rd,Rr Fractional Multiply Signed R1:R0 ← (Rd × Rr)<<1 (SS) Z,C 2 (1)

FMULSU Rd,Rr Fractional Multiply Signed with

Unsigned

R1:R0 ← (Rd × Rr)<<1 (SU) Z,C 2 (1)

Branch Instructions

RJMP k Relative Jump PC ← PC + k + 1 None 2

IJMP Indirect Jump to (Z) PC(15:0) ← Z, PC(21:16) ← 0None 2 (1)

12 AVR Instruction Set

0856E–AVR–11/05

EIJMP Extended Indirect Jump to (Z) PC(15:0) ← Z, PC(21:16) ← EIND None 2 (1)

JMP k Jump PC ← k None 3 (1)

RCALL k Relative Call Subroutine PC ← PC + k + 1 None 3 / 4 (4)

ICALL Indirect Call to (Z) PC(15:0) ← Z, PC(21:16) ← 0 None 3 / 4 (1)(4)

EICALL Extended Indirect Call to (Z) PC(15:0) ← Z, PC(21:16) ← EIND None 4 (1)(4)

CALL k Call Subroutine PC ← k None 4 / 5 (1)(4)

RET Subroutine Return PC ← STACK None 4 / 5 (4)

RETI Interrupt Return PC ← STACK I 4 / 5 (4)

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,C,N,V,S,H 1

CPC Rd,Rr Compare with Carry Rd - Rr - C Z,C,N,V,S,H 1

CPI Rd,K Compare with Immediate Rd - K Z,C,N,V,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 Set if (Rr(b)=1) PC ← PC + 2 or 3 None 1 / 2 / 3

SBIC A, b Skip if Bit in I/O Register Cleared if(I/O(A,b)=0) PC ← PC + 2 or 3 None 1 / 2 / 3

SBIS A, b Skip if Bit in I/O Register 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, 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

Instruction Set Summary (Continued)

Mnemonics Operands Description Operation Flags

#Clock

Note

AVR Instruction Set

0856E–AVR–11/05

BRID k Branch if Interrupt Disabled if ( I = 0) then PC ← PC + k + 1 None 1 / 2

Data Transfer Instructions

MOV Rd, Rr Copy Register Rd ← Rr None 1

MOVW Rd, Rr Copy Register Pair Rd+1:Rd ← Rr+1:Rr None 1 (1)

LDI Rd, K Load Immediate Rd ← KNone1

LDS Rd, k Load Direct from data space Rd ← (k) None 2 (1)(4)

LD Rd, X Load Indirect Rd ← (X) None 2 (2)(4)

LD Rd, X+ Load Indirect and Post-Increment Rd ← (X), X ← X + 1 None 2 (2)(4)

LD Rd, -X Load Indirect and Pre-Decrement X ← X - 1, Rd ← (X) None 2 (2)(4)

LD Rd, Y Load Indirect Rd ← (Y) None 2 (2)(4)

LD Rd, Y+ Load Indirect and Post-Increment Rd ← (Y), Y ← Y + 1 None 2 (2)(4)

LD Rd, -Y Load Indirect and Pre-Decrement Y ← Y - 1, Rd ← (Y) None 2 (2)(4)

LDD Rd,Y+q Load Indirect with Displacement Rd ← (Y + q) None 2 (1)(4)

LD Rd, Z Load Indirect Rd ← (Z) None 2 (2)(4)

LD Rd, Z+ Load Indirect and Post-Increment Rd ← (Z), Z ← Z+1 None 2 (2)(4)

LD Rd, -Z Load Indirect and Pre-Decrement Z ← Z - 1, Rd ← (Z) None 2 (2)(4)

LDD Rd, Z+q Load Indirect with Displacement Rd ← (Z + q) None 2 (1)(4)

STS k, Rr Store Direct to data space (k) ← Rd None 2 (1)(4)

ST X, Rr Store Indirect (X) ← Rr None 2 (2)(4)

ST X+, Rr Store Indirect and Post-Increment (X) ← Rr, X ← X + 1 None 2 (2)(4)

ST -X, Rr Store Indirect and Pre-Decrement X ← X - 1, (X) ← Rr None 2 (2)(4)

ST Y, Rr Store Indirect (Y) ← Rr None 2 (2)(4)

ST Y+, Rr Store Indirect and Post-Increment (Y) ← Rr, Y ← Y + 1 None 2 (2)(4)

ST -Y, Rr Store Indirect and Pre-Decrement Y ← Y - 1, (Y) ← Rr None 2 (2)(4)

STD Y+q,Rr Store Indirect with Displacement (Y + q) ← Rr None 2 (1)(4)

ST Z, Rr Store Indirect (Z) ← Rr None 2 (2)(4)

ST Z+, Rr Store Indirect and Post-Increment (Z) ← Rr, Z ← Z + 1 None 2 (2)(4)

ST -Z, Rr Store Indirect and Pre-Decrement Z ← Z - 1, (Z) ← Rr None 2 (2)(4)

STD Z+q,Rr Store Indirect with Displacement (Z + q) ← Rr None 2 (1)(4)

LPM Load Program Memory R0 ← (Z) None 3 (3)

LPM Rd, Z Load Program Memory Rd ← (Z) None 3 (3)

LPM Rd, Z+ Load Program Memory and Post-

Increment

Rd ← (Z), Z ← Z + 1 None 3 (3)

ELPM Extended Load Program Memory R0 ← (RAMPZ:Z) None 3 (1)

ELPM Rd, Z Extended Load Program Memory Rd ← (RAMPZ:Z) None 3 (1)

Instruction Set Summary (Continued)

Mnemonics Operands Description Operation Flags

#Clock

Note

14 AVR Instruction Set

0856E–AVR–11/05

ELPM Rd, Z+ Extended Load Program Memory

and Post-Increment

Rd ← (RAMPZ:Z), Z ← Z + 1 None 3 (1)

SPM Store Program Memory (Z) ← R1:R0 None - (1)

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 (1)

POP Rd Pop Register from Stack Rd ← STACK None 2 (1)

Bit and Bit-test Instructions

LSL Rd Logical Shift Left Rd(n+1)←Rd(n),Rd(0)←0,C←Rd(7) Z,C,N,V,H 1

LSR Rd Logical Shift Right Rd(n)←Rd(n+1),Rd(7)←0,C←Rd(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,H 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) 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) ← 1None2

CBI A, b Clear Bit in I/O Register I/O(A, b) ← 0None2

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) ← TNone1

SEC Set Carry C ← 1C1

CLC Clear Carry C ← 0 C 1

SEN Set Negative Flag N ← 1N1

CLN Clear Negative Flag N ← 0 N 1

SEZ Set Zero Flag Z ← 1Z1

CLZ Clear Zero Flag Z ← 0 Z 1

SEI Global Interrupt Enable I ← 1I1

CLI Global Interrupt Disable I ← 0 I 1

SES Set Signed Test Flag S ← 1S1

CLS Clear Signed Test Flag S ← 0 S 1

SEV Set Two’s Complement Overflow V ← 1V1

CLV Clear Two’s Complement Overflow V ← 0 V 1

SET Set T in SREG T ← 1T1

CLT Clear T in SREG T ← 0 T 1

SEH Set Half Carry Flag in SREG H ← 1H1

CLH Clear Half Carry Flag in SREG H ← 0 H 1

Instruction Set Summary (Continued)

Mnemonics Operands Description Operation Flags

#Clock

Note

AVR Instruction Set

0856E–AVR–11/05

Notes: 1. This instruction is not available in all devices. Refer to the device specific instruction set summary.

2. Not all variants of this instruction are available in all devices. Refer to the device specific instruction set summary.

3. Not all variants of the LPM instruction are available in all devices. Refer to the device specific instruction set summary. The

LPM instruction is not implemented at all in the AT90S1200 device.

4. Cycle times for Data memory accesses assume internal memory accesses, and are not valid for accesses via the external

RAM interface. For LD, ST, LDS, STS, PUSH, POP, add one cycle plus one cycle for each wait state. For CALL, ICALL,

EICALL, RCALL, RET, RETI in devices with 16-bit PC, add three cycles plus two cycles for each wait state. For CALL,

ICALL, EICALL, RCALL, RET, RETI in devices with 22-bit PC, add five cycles plus three cycles for each wait state.

MCU Control Instructions

BREAK Break (See specific descr. for BREAK) None 1 (1)

NOP No Operation None 1

SLEEP Sleep (see specific descr. for Sleep) None 1

WDR Watchdog Reset (see specific descr. for WDR) None 1

Instruction Set Summary (Continued)

Mnemonics Operands Description Operation Flags

#Clock

Note

16 AVR Instruction Set

0856E–AVR–11/05

ADC – Add with Carry

Description:

Adds two registers and the contents of the C Flag and places the result in the destination register Rd.

Operation:

(i) Rd ← Rd + Rr + C

Syntax: Operands: Program Counter:

(i) ADC Rd,Rr 0 ≤ d ≤ 31, 0 ≤ r ≤ 31 PC ← PC + 1

16-bit Opcode:

Status Register (SREG) Boolean Formula:

H: Rd3•Rr3+Rr3•R3+R3•Rd3

Set if there was a carry from bit 3; cleared otherwise

S: N ⊕ V, For signed tests.

V: Rd7•Rr7•R7+Rd7•Rr7•R7

Set if two’s complement overflow resulted from the operation; cleared otherwise.

N: R7

Set if MSB of the result is set; cleared otherwise.

Z: R7• R6 •R5• R4 •R3 •R2 •R1 •R0

Set if the result is $00; cleared otherwise.

C: Rd7•Rr7+Rr7•R7+R7•Rd7

Set if there was carry from the MSB of the result; cleared otherwise.

R (Result) equals Rd after the operation.

Example:

; Add R1:R0 to R3:R2

add r2,r0 ; Add low byte

adc r3,r1 ; Add with carry high byte

Words: 1 (2 bytes)

Cycles: 1

0001 11rd dddd rrrr

ITHSVNZC

––⇔⇔⇔⇔⇔⇔

AVR Instruction Set

0856E–AVR–11/05

ADD – Add without Carry

Description:

Adds two registers without the C Flag and places the result in the destination register Rd.

Operation:

(i) Rd ← Rd + Rr

Syntax: Operands: Program Counter:

(i) ADD Rd,Rr 0 ≤ d ≤ 31, 0 ≤ r ≤ 31 PC ← PC + 1

16-bit Opcode:

Status Register (SREG) and Boolean Formula:

H: Rd3•Rr3+Rr3•R3+R3•Rd3

Set if there was a carry from bit 3; cleared otherwise

S: N ⊕ V, For signed tests.

V: Rd7•Rr7•R7+Rd7•Rr7•R7

Set if two’s complement overflow resulted from the operation; cleared otherwise.

N: R7

Set if MSB of the result is set; cleared otherwise.

Z: R7• R6 •R5• R4 •R3 •R2 •R1 •R0

Set if the result is $00; cleared otherwise.

C: Rd7 •Rr7 +Rr7 •R7+ R7 •Rd7

Set if there was carry from the MSB of the result; cleared otherwise.

R (Result) equals Rd after the operation.

Example:

add r1,r2 ; Add r2 to r1 (r1=r1+r2)

add r28,r28 ; Add r28 to itself (r28=r28+r28)

Words: 1 (2 bytes)

Cycles: 1

0000 11rd dddd rrrr

ITHSVNZC

––⇔⇔⇔⇔⇔⇔

18 AVR Instruction Set

0856E–AVR–11/05

ADIW – Add Immediate to Word

Description:

Adds an immediate value (0 - 63) to a register pair and places the result in the register pair. This instruction operates on the

upper four register pairs, and is well suited for operations on the pointer registers.

This instruction is not available in all devices. Refer to the device specific instruction set summary.

Operation:

(i) Rd+1:Rd ← Rd+1:Rd + K

Syntax: Operands: Program Counter:

(i) ADIW Rd+1:Rd,K d ∈ {24,26,28,30}, 0 ≤ K ≤ 63 PC ← PC + 1

16-bit Opcode:

Status Register (SREG) and Boolean Formula:

S: N ⊕ V, For signed tests.

V: Rdh7 • R15

Set if two’s complement overflow resulted from the operation; cleared otherwise.

N: R15

Set if MSB of the result is set; cleared otherwise.

Z: R15 •R14 •R13 •R12 •R11 •R10 •R9 •R8 •R7• R6• R5• R4• R3• R2 •R1• R0

Set if the result is $0000; cleared otherwise.

C: R15 • Rdh7

Set if there was carry from the MSB of the result; cleared otherwise.

R (Result) equals Rdh:Rdl after the operation (Rdh7-Rdh0 = R15-R8, Rdl7-Rdl0=R7-R0).

Example:

adiw r25:24,1 ; Add 1 to r25:r24

adiw ZH:ZL,63 ; Add 63 to the Z-pointer(r31:r30)

Words: 1 (2 bytes)

Cycles: 2

1001 0110 KKdd KKKK

ITHSVNZC

–– –⇔⇔⇔⇔⇔

AVR Instruction Set

0856E–AVR–11/05

AND – Logical AND

Description:

Performs the logical AND between the contents of register Rd and register Rr and places the result in the destination regis-

ter Rd.

Operation:

(i) Rd ← Rd • Rr

Syntax: Operands: Program Counter:

(i) AND Rd,Rr 0 ≤ d ≤ 31, 0 ≤ r ≤ 31 PC ← PC + 1

16-bit Opcode:

Status Register (SREG) and Boolean Formula:

S: N ⊕ V, For signed tests.

V: 0

Cleared

N: R7

Set if MSB of the result is set; cleared otherwise.

Z: R7 •R6 •R5 •R4 •R3• R2 •R1 •R0

Set if the result is $00; cleared otherwise.

R (Result) equals Rd after the operation.

Example:

and r2,r3 ; Bitwise and r2 and r3, result in r2

ldi r16,1 ; Set bitmask 0000 0001 in r16

and r2,r16 ; Isolate bit 0 in r2

Words: 1 (2 bytes)

Cycles: 1

0010 00rd dddd rrrr

ITHSVNZC

–– –⇔0⇔⇔ –

20 AVR Instruction Set

0856E–AVR–11/05

ANDI – Logical AND with Immediate

Description:

Performs the logical AND between the contents of register Rd and a constant and places the result in the destination regis-

ter Rd.

Operation:

(i) Rd ← Rd • K

Syntax: Operands: Program Counter:

(i) ANDI Rd,K 16 ≤ d ≤ 31, 0 ≤ K ≤ 255 PC ← PC + 1

16-bit Opcode:

Status Register (SREG) and Boolean Formula:

S: N ⊕ V, For signed tests.

V: 0

Cleared

N: R7

Set if MSB of the result is set; cleared otherwise.

Z: R7 •R6• R5•R4 •R3• R2• R1• R0

Set if the result is $00; cleared otherwise.

R (Result) equals Rd after the operation.

Example:

andi r17,$0F ; Clear upper nibble of r17

andi r18,$10 ; Isolate bit 4 in r18

andi r19,$AA ; Clear odd bits of r19

Words: 1 (2 bytes)

Cycles: 1

0111 KKKK dddd KKKK

ITHSVNZC

–– –⇔0⇔⇔ –

AVR Instruction Set

0856E–AVR–11/05

ASR – Arithmetic Shift Right

Description:

Shifts all bits in Rd one place to the right. Bit 7 is held constant. Bit 0 is loaded into the C Flag of the SREG. This operation

effectively divides a signed value by two without changing its sign. The Carry Flag can be used to round the result.

Operation:

(i)

Syntax: Operands: Program Counter:

(i) ASR Rd 0 ≤ d ≤ 31 PC ← PC + 1

16-bit Opcode:

Status Register (SREG) and Boolean Formula:

S: N ⊕ V, For signed tests.

V: N ⊕ C (For N and C after the shift)

N: R7

Set if MSB of the result is set; cleared otherwise.

Z: R7 •R6 •R5• R4 •R3 •R2• R1• R0

Set if the result is $00; cleared otherwise.

C: Rd0

Set if, before the shift, the LSB of Rd was set; cleared otherwise.

R (Result) equals Rd after the operation.

Example:

ldi r16,$10 ; Load decimal 16 into r16

asr r16 ; r16=r16 / 2

ldi r17,$FC ; Load -4 in r17

asr r17 ; r17=r17/2

Words: 1 (2 bytes)

Cycles: 1

1001 010d dddd 0101

ITHSVNZC

–– –⇔⇔⇔⇔⇔

b7-------------------b0 C

22 AVR Instruction Set

0856E–AVR–11/05

BCLR – Bit Clear in SREG

Description:

Clears a single Flag in SREG.

Operation:

(i) SREG(s) ← 0

Syntax: Operands: Program Counter:

(i) BCLR s 0 ≤ s ≤ 7PC ← PC + 1

16-bit Opcode:

Status Register (SREG) and Boolean Formula:

I: 0 if s = 7; Unchanged otherwise.

T: 0 if s = 6; Unchanged otherwise.

H: 0 if s = 5; Unchanged otherwise.

S: 0 if s = 4; Unchanged otherwise.

V: 0 if s = 3; Unchanged otherwise.

N: 0 if s = 2; Unchanged otherwise.

Z: 0 if s = 1; Unchanged otherwise.

C: 0 if s = 0; Unchanged otherwise.

Example:

bclr 0 ; Clear Carry Flag

bclr 7 ; Disable interrupts

Words: 1 (2 bytes)

Cycles: 1

1001 0100 1sss 1000

ITHSVNZC

⇔⇔⇔⇔⇔⇔⇔⇔

AVR Instruction Set

0856E–AVR–11/05

BLD – Bit Load from the T Flag in SREG to a Bit in Register

Description:

Copies the T Flag in the SREG (Status Register) to bit b in register Rd.

Operation:

(i) Rd(b) ← T

Syntax: Operands: Program Counter:

(i) BLD Rd,b 0 ≤ d ≤ 31, 0 ≤ b ≤ 7PC ← PC + 1

16 bit Opcode:

Status Register (SREG) and Boolean Formula:

Example:

; Copy bit

bst r1,2 ; Store bit 2 of r1 in T Flag

bld r0,4 ; Load T Flag into bit 4 of r0

Words: 1 (2 bytes)

Cycles: 1

1111 100d dddd 0bbb

ITHSVNZC

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24 AVR Instruction Set

0856E–AVR–11/05

BRBC – Branch if Bit in SREG is Cleared

Description:

Conditional relative branch. Tests a single bit in SREG and branches relatively to PC if the bit is cleared. This instruction

branches relatively to PC in either direction (PC - 63 ≤ destination ≤ PC + 64). The parameter k is the offset from PC and is

represented in two’s complement form.

Operation:

(i) If SREG(s) = 0 then PC ← PC + k + 1, else PC ← PC + 1

Syntax: Operands: Program Counter:

(i) BRBC s,k 0 ≤ s ≤ 7, -64 ≤ k ≤ +63 PC ← PC + k + 1

PC ← PC + 1, if condition is false

16-bit Opcode:

Status Register (SREG) and Boolean Formula:

Example:

cpi r20,5 ; Compare r20 to the value 5

brbc 1,noteq ; Branch if Zero Flag cleared

...

noteq:nop ; Branch destination (do nothing)

Words: 1 (2 bytes)

Cycles: 1 if condition is false

2 if condition is true

1111 01kk kkkk ksss

ITHSVNZC

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AVR Instruction Set

0856E–AVR–11/05

BRBS – Branch if Bit in SREG is Set

Description:

Conditional relative branch. Tests a single bit in SREG and branches relatively to PC if the bit is set. This instruction

branches relatively to PC in either direction (PC - 63 ≤ destination ≤ PC + 64). The parameter k is the offset from PC and is

represented in two’s complement form.

Operation:

(i) If SREG(s) = 1 then PC ← PC + k + 1, else PC ← PC + 1

Syntax: Operands: Program Counter:

(i) BRBS s,k 0 ≤ s ≤ 7, -64 ≤ k ≤ +63 PC ← PC + k + 1

PC ← PC + 1, if condition is false

16-bit Opcode:

Status Register (SREG) and Boolean Formula:

Example:

bst r0,3 ; Load T bit with bit 3 of r0

brbs 6,bitset ; Branch T bit was set

...

bitset: nop ; Branch destination (do nothing)

Words: 1 (2 bytes)

Cycles: 1 if condition is false

2 if condition is true

1111 00kk kkkk ksss

ITHSVNZC

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26 AVR Instruction Set

0856E–AVR–11/05

BRCC – Branch if Carry Cleared

Description:

Conditional relative branch. Tests the Carry Flag (C) and branches relatively to PC if C is cleared. This instruction branches

relatively to PC in either direction (PC - 63 ≤ destination ≤ PC + 64). The parameter k is the offset from PC and is repre-

sented in two’s complement form. (Equivalent to instruction BRBC 0,k).

Operation:

(i) If C = 0 then PC ← PC + k + 1, else PC ← PC + 1

Syntax: Operands: Program Counter:

(i) BRCC k -64 ≤ k ≤ +63 PC ← PC + k + 1

PC ← PC + 1, if condition is false

16-bit Opcode:

Status Register (SREG) and Boolean Formula:

Example:

add r22,r23 ; Add r23 to r22

brcc nocarry ; Branch if carry cleared

...

nocarry: nop ; Branch destination (do nothing)

Words: 1 (2 bytes)

Cycles: 1 if condition is false

2 if condition is true

1111 01kk kkkk k000

ITHSVNZC

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AVR Instruction Set

0856E–AVR–11/05

BRCS – Branch if Carry Set

Description:

Conditional relative branch. Tests the Carry Flag (C) and branches relatively to PC if C is set. This instruction branches rel-

atively to PC in either direction (PC - 63 ≤ destination ≤ PC + 64). The parameter k is the offset from PC and is represented

in two’s complement form. (Equivalent to instruction BRBS 0,k).

Operation:

(i) If C = 1 then PC ← PC + k + 1, else PC ← PC + 1

Syntax: Operands: Program Counter:

(i) BRCS k -64 ≤ k ≤ +63 PC ← PC + k + 1

PC ← PC + 1, if condition is false

16-bit Opcode:

Status Register (SREG) and Boolean Formula:

Example:

cpi r26,$56 ; Compare r26 with $56

brcs carry ; Branch if carry set

...

carry: nop ; Branch destination (do nothing)

Words: 1 (2 bytes)

Cycles: 1 if condition is false

2 if condition is true

1111 00kk kkkk k000

ITHSVNZC

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28 AVR Instruction Set

0856E–AVR–11/05

BREAK – Break

Description:

The BREAK instruction is used by the On-chip Debug system, and is normally not used in the application software. When

the BREAK instruction is executed, the AVR CPU is set in the Stopped Mode. This gives the On-chip Debugger access to

internal resources.

If any Lock bits are set, or either the JTAGEN or OCDEN Fuses are unprogrammed, the CPU will treat the BREAK instruc-

tion as a NOP and will not enter the Stopped mode.

This instruction is not available in all devices. Refer to the device specific instruction set summary.

Operation:

(i) On-chip Debug system break.

Syntax: Operands: Program Counter:

(i) BREAK None PC ← PC + 1

16-bit Opcode:

Status Register (SREG) and Boolean Formula:

Words: 1 (2 bytes)

Cycles: 1

1001 0101 1001 1000

ITHSVNZC

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AVR Instruction Set

0856E–AVR–11/05

BREQ – Branch if Equal

Description:

Conditional relative branch. Tests the Zero Flag (Z) and branches relatively to PC if Z is set. If the instruction is executed

immediately after any of the instructions CP, CPI, SUB or SUBI, the branch will occur if and only if the unsigned or signed

binary number represented in Rd was equal to the unsigned or signed binary number represented in Rr. This instruction

branches relatively to PC in either direction (PC - 63 ≤ destination ≤ PC + 64). The parameter k is the offset from PC and is

represented in two’s complement form. (Equivalent to instruction BRBS 1,k).

Operation:

(i) If Rd = Rr (Z = 1) then PC ← PC + k + 1, else PC ← PC + 1

Syntax: Operands: Program Counter:

(i) BREQ k -64 ≤ k ≤ +63 PC ← PC + k + 1

PC ← PC + 1, if condition is false

16-bit Opcode:

Status Register (SREG) and Boolean Formula:

Example:

cp r1,r0 ; Compare registers r1 and r0

breq equal ; Branch if registers equal

...

equal: nop ; Branch destination (do nothing)

Words: 1 (2 bytes)

Cycles: 1 if condition is false

2 if condition is true

1111 00kk kkkk k001

ITHSVNZC

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30 AVR Instruction Set

0856E–AVR–11/05

BRGE – Branch if Greater or Equal (Signed)

Description:

Conditional relative branch. Tests the Signed Flag (S) and branches relatively to PC if S is cleared. If the instruction is exe-

cuted immediately after any of the instructions CP, CPI, SUB or SUBI, the branch will occur if and only if the signed binary

number represented in Rd was greater than or equal to the signed binary number represented in Rr. This instruction

branches relatively to PC in either direction (PC - 63 ≤ destination ≤ PC + 64). The parameter k is the offset from PC and is

represented in two’s complement form. (Equivalent to instruction BRBC 4,k).

Operation:

(i) If Rd ≥ Rr (N ⊕ V = 0) then PC ← PC + k + 1, else PC ← PC + 1

Syntax: Operands: Program Counter:

(i) BRGE k -64 ≤ k ≤ +63 PC ← PC + k + 1

PC ← PC + 1, if condition is false

16-bit Opcode:

Status Register (SREG) and Boolean Formula:

Example:

cp r11,r12 ; Compare registers r11 and r12

brge greateq ; Branch if r11 ≥ r12 (signed)

...

greateq: nop ; Branch destination (do nothing)

Words: 1 (2 bytes)

Cycles: 1 if condition is false

2 if condition is true

1111 01kk kkkk k100

ITHSVNZC

––––––––

AVR Instruction Set

0856E–AVR–11/05

BRHC – Branch if Half Carry Flag is Cleared

Description:

Conditional relative branch. Tests the Half Carry Flag (H) and branches relatively to PC if H is cleared. This instruction

branches relatively to PC in either direction (PC - 63 ≤ destination ≤ PC + 64). The parameter k is the offset from PC and is

represented in two’s complement form. (Equivalent to instruction BRBC 5,k).

Operation:

(i) If H = 0 then PC ← PC + k + 1, else PC ← PC + 1

Syntax: Operands: Program Counter:

(i) BRHC k -64 ≤ k ≤ +63 PC ← PC + k + 1

PC ← PC + 1, if condition is false

16-bit Opcode:

Status Register (SREG) and Boolean Formula:

Example:

brhc hclear ; Branch if Half Carry Flag cleared

...

hclear: nop ; Branch destination (do nothing)

Words: 1 (2 bytes)

Cycles: 1 if condition is false

2 if condition is true

1111 01kk kkkk k101

ITHSVNZC

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32 AVR Instruction Set

0856E–AVR–11/05

BRHS – Branch if Half Carry Flag is Set

Description:

Conditional relative branch. Tests the Half Carry Flag (H) and branches relatively to PC if H is set. This instruction branches

relatively to PC in either direction (PC - 63 ≤ destination ≤ PC + 64). The parameter k is the offset from PC and is repre-

sented in two’s complement form. (Equivalent to instruction BRBS 5,k).

Operation:

(i) If H = 1 then PC ← PC + k + 1, else PC ← PC + 1

Syntax: Operands: Program Counter:

(i) BRHS k -64 ≤ k ≤ +63 PC ← PC + k + 1

PC ← PC + 1, if condition is false

16-bit Opcode:

Status Register (SREG) and Boolean Formula:

Example:

brhs hset ; Branch if Half Carry Flag set

...

hset: nop ; Branch destination (do nothing)

Words: 1 (2 bytes)

Cycles: 1 if condition is false

2 if condition is true

1111 00kk kkkk k101

ITHSVNZC

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AVR Instruction Set

0856E–AVR–11/05

BRID – Branch if Global Interrupt is Disabled

Description:

Conditional relative branch. Tests the Global Interrupt Flag (I) and branches relatively to PC if I is cleared. This instruction

branches relatively to PC in either direction (PC - 63 ≤ destination ≤ PC + 64). The parameter k is the offset from PC and is

represented in two’s complement form. (Equivalent to instruction BRBC 7,k).

Operation:

(i) If I = 0 then PC ← PC + k + 1, else PC ← PC + 1

Syntax: Operands: Program Counter:

(i) BRID k -64 ≤ k ≤ +63 PC ← PC + k + 1

PC ← PC + 1, if condition is false

16-bit Opcode:

Status Register (SREG) and Boolean Formula:

Example:

brid intdis ; Branch if interrupt disabled

...

intdis: nop ; Branch destination (do nothing)

Words: 1 (2 bytes)

Cycles: 1 if condition is false

2 if condition is true

1111 01kk kkkk k111

ITHSVNZC

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34 AVR Instruction Set

0856E–AVR–11/05

BRIE – Branch if Global Interrupt is Enabled

Description:

Conditional relative branch. Tests the Global Interrupt Flag (I) and branches relatively to PC if I is set. This instruction

branches relatively to PC in either direction (PC - 63 ≤ destination ≤ PC + 64). The parameter k is the offset from PC and is

represented in two’s complement form. (Equivalent to instruction BRBS 7,k).

Operation:

(i) If I = 1 then PC ← PC + k + 1, else PC ← PC + 1

Syntax: Operands: Program Counter:

(i) BRIE k -64 ≤ k ≤ +63 PC ← PC + k + 1

PC ← PC + 1, if condition is false

16-bit Opcode:

Status Register (SREG) and Boolean Formula:

Example:

brie inten ; Branch if interrupt enabled

...

inten: nop ; Branch destination (do nothing)

Words: 1 (2 bytes)

Cycles: 1 if condition is false

2 if condition is true

1111 00kk kkkk k111

ITHSVNZC

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AVR Instruction Set

0856E–AVR–11/05

BRLO – Branch if Lower (Unsigned)

Description:

Conditional relative branch. Tests the Carry Flag (C) and branches relatively to PC if C is set. If the instruction is executed

immediately after any of the instructions CP, CPI, SUB or SUBI, the branch will occur if and only if the unsigned binary

number represented in Rd was smaller than the unsigned binary number represented in Rr. This instruction branches rela-

tively to PC in either direction (PC - 63 ≤ destination ≤ PC + 64). The parameter k is the offset from PC and is represented

in two’s complement form. (Equivalent to instruction BRBS 0,k).

Operation:

(i) If Rd < Rr (C = 1) then PC ← PC + k + 1, else PC ← PC + 1

Syntax: Operands: Program Counter:

(i) BRLO k -64 ≤ k ≤ +63 PC ← PC + k + 1

PC ← PC + 1, if condition is false

16-bit Opcode:

Status Register (SREG) and Boolean Formula:

Example:

eor r19,r19 ; Clear r19

loop: inc r19 ; Increase r19

...

cpi r19,$10 ; Compare r19 with $10

brlo loop ; Branch if r19 < $10 (unsigned)

nop ; Exit from loop (do nothing)

Words: 1 (2 bytes)

Cycles: 1 if condition is false

2 if condition is true

1111 00kk kkkk k000

ITHSVNZC

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36 AVR Instruction Set

0856E–AVR–11/05

BRLT – Branch if Less Than (Signed)

Description:

Conditional relative branch. Tests the Signed Flag (S) and branches relatively to PC if S is set. If the instruction is executed

immediately after any of the instructions CP, CPI, SUB or SUBI, the branch will occur if and only if the signed binary num-

ber represented in Rd was less than the signed binary number represented in Rr. This instruction branches relatively to PC

in either direction (PC - 63 ≤ destination ≤ PC + 64). The parameter k is the offset from PC and is represented in two’s com-

plement form. (Equivalent to instruction BRBS 4,k).

Operation:

(i) If Rd < Rr (N ⊕ V = 1) then PC ← PC + k + 1, else PC ← PC + 1

Syntax: Operands: Program Counter:

(i) BRLT k -64 ≤ k ≤ +63 PC ← PC + k + 1

PC ← PC + 1, if condition is false

16-bit Opcode:

Status Register (SREG) and Boolean Formula:

Example:

cp r16,r1 ; Compare r16 to r1

brlt less ; Branch if r16 < r1 (signed)

...

less: nop ; Branch destination (do nothing)

Words: 1 (2 bytes)

Cycles: 1 if condition is false

2 if condition is true

1111 00kk kkkk k100

ITHSVNZC

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AVR Instruction Set

0856E–AVR–11/05

BRMI – Branch if Minus

Description:

Conditional relative branch. Tests the Negative Flag (N) and branches relatively to PC if N is set. This instruction branches

relatively to PC in either direction (PC - 63 ≤ destination ≤ PC + 64). The parameter k is the offset from PC and is repre-

sented in two’s complement form. (Equivalent to instruction BRBS 2,k).

Operation:

(i) If N = 1 then PC ← PC + k + 1, else PC ← PC + 1

Syntax: Operands: Program Counter:

(i) BRMI k -64 ≤ k ≤ +63 PC ← PC + k + 1

PC ← PC + 1, if condition is false

16-bit Opcode:

Status Register (SREG) and Boolean Formula:

Example:

subi r18,4 ; Subtract 4 from r18

brmi negative ; Branch if result negative

...

negative: nop ; Branch destination (do nothing)

Words: 1 (2 bytes)

Cycles: 1 if condition is false

2 if condition is true

1111 00kk kkkk k010

ITHSVNZC

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38 AVR Instruction Set

0856E–AVR–11/05

BRNE – Branch if Not Equal

Description:

Conditional relative branch. Tests the Zero Flag (Z) and branches relatively to PC if Z is cleared. If the instruction is exe-

cuted immediately after any of the instructions CP, CPI, SUB or SUBI, the branch will occur if and only if the unsigned or

signed binary number represented in Rd was not equal to the unsigned or signed binary number represented in Rr. This

instruction branches relatively to PC in either direction (PC - 63 ≤ destination ≤ PC + 64). The parameter k is the offset from

PC and is represented in two’s complement form. (Equivalent to instruction BRBC 1,k).

Operation:

(i) If Rd ≠ Rr (Z = 0) then PC ← PC + k + 1, else PC ← PC + 1

Syntax: Operands: Program Counter:

(i) BRNE k -64 ≤ k ≤ +63 PC ← PC + k + 1

PC ← PC + 1, if condition is false

16-bit Opcode:

Status Register (SREG) and Boolean Formula:

Example:

eor r27,r27 ; Clear r27

loop: inc r27 ; Increase r27

...

cpi r27,5 ; Compare r27 to 5

brne loop ; Branch if r27<>5

nop ; Loop exit (do nothing)

Words: 1 (2 bytes)

Cycles: 1 if condition is false

2 if condition is true

1111 01kk kkkk k001

ITHSVNZC

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AVR Instruction Set

0856E–AVR–11/05

BRPL – Branch if Plus

Description:

Conditional relative branch. Tests the Negative Flag (N) and branches relatively to PC if N is cleared. This instruction

branches relatively to PC in either direction (PC - 63 ≤ destination ≤ PC + 64). The parameter k is the offset from PC and is

represented in two’s complement form. (Equivalent to instruction BRBC 2,k).

Operation:

(i) If N = 0 then PC ← PC + k + 1, else PC ← PC + 1

Syntax: Operands: Program Counter:

(i) BRPL k -64 ≤ k ≤ +63 PC ← PC + k + 1

PC ← PC + 1, if condition is false

16-bit Opcode:

Status Register (SREG) and Boolean Formula:

Example:

subi r26,$50 ; Subtract $50 from r26

brpl positive ; Branch if r26 positive

...

positive: nop ; Branch destination (do nothing)

Words: 1 (2 bytes)

Cycles: 1 if condition is false

2 if condition is true

1111 01kk kkkk k010

ITHSVNZC

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40 AVR Instruction Set

0856E–AVR–11/05

BRSH – Branch if Same or Higher (Unsigned)

Description:

Conditional relative branch. Tests the Carry Flag (C) and branches relatively to PC if C is cleared. If the instruction is exe-

cuted immediately after execution of any of the instructions CP, CPI, SUB or SUBI the branch will occur if and only if the

unsigned binary number represented in Rd was greater than or equal to the unsigned binary number represented in Rr.

This instruction branches relatively to PC in either direction (PC - 63 ≤ destination ≤ PC + 64). The parameter k is the offset

from PC and is represented in two’s complement form. (Equivalent to instruction BRBC 0,k).

Operation:

(i) If Rd ≥Rr (C = 0) then PC ← PC + k + 1, else PC ← PC + 1

Syntax: Operands: Program Counter:

(i) BRSH k -64 ≤ k ≤ +63 PC ← PC + k + 1

PC ← PC + 1, if condition is false

16-bit Opcode:

Status Register (SREG) and Boolean Formula:

Example:

subi r19,4 ; Subtract 4 from r19

brsh highsm ; Branch if r19 >= 4 (unsigned)

...

highsm: nop ; Branch destination (do nothing)

Words: 1 (2 bytes)

Cycles: 1 if condition is false

2 if condition is true

1111 01kk kkkk k000

ITHSVNZC

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AVR Instruction Set

0856E–AVR–11/05

BRTC – Branch if the T Flag is Cleared

Description:

Conditional relative branch. Tests the T Flag and branches relatively to PC if T is cleared. This instruction branches rela-

tively to PC in either direction (PC - 63 ≤ destination ≤ PC + 64). The parameter k is the offset from PC and is represented

in two’s complement form. (Equivalent to instruction BRBC 6,k).

Operation:

(i) If T = 0 then PC ← PC + k + 1, else PC ← PC + 1

Syntax: Operands: Program Counter:

(i) BRTC k -64 ≤ k ≤ +63 PC ← PC + k + 1

PC ← PC + 1, if condition is false

16-bit Opcode:

Status Register (SREG) and Boolean Formula:

Example:

bst r3,5 ; Store bit 5 of r3 in T Flag

brtc tclear ; Branch if this bit was cleared

...

tclear: nop ; Branch destination (do nothing)

Words: 1 (2 bytes)

Cycles: 1 if condition is false

2 if condition is true

1111 01kk kkkk k110

ITHSVNZC

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42 AVR Instruction Set

0856E–AVR–11/05

BRTS – Branch if the T Flag is Set

Description:

Conditional relative branch. Tests the T Flag and branches relatively to PC if T is set. This instruction branches relatively to

PC in either direction (PC - 63 ≤ destination ≤ PC + 64). The parameter k is the offset from PC and is represented in two’s

complement form. (Equivalent to instruction BRBS 6,k).

Operation:

(i) If T = 1 then PC ← PC + k + 1, else PC ← PC + 1

Syntax: Operands: Program Counter:

(i) BRTS k -64 ≤ k ≤ +63 PC ← PC + k + 1

PC ← PC + 1, if condition is false

16-bit Opcode:

Status Register (SREG) and Boolean Formula:

Example:

bst r3,5 ; Store bit 5 of r3 in T Flag

brts tset ; Branch if this bit was set

...

tset: nop ; Branch destination (do nothing)

Words: 1 (2 bytes)

Cycles: 1 if condition is false

2 if condition is true

1111 00kk kkkk k110

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AVR Instruction Set

0856E–AVR–11/05

BRVC – Branch if Overflow Cleared

Description:

Conditional relative branch. Tests the Overflow Flag (V) and branches relatively to PC if V is cleared. This instruction branch-

es relatively to PC in either direction (PC - 63 ≤ destination ≤ PC + 64). The parameter k is the offset from PC and is repre-

sented in two’s complement form. (Equivalent to instruction BRBC 3,k).

Operation:

(i) If V = 0 then PC ← PC + k + 1, else PC ← PC + 1

Syntax: Operands: Program Counter:

(i) BRVC k -64 ≤ k ≤ +63 PC ← PC + k + 1

PC ← PC + 1, if condition is false

16-bit Opcode:

Status Register (SREG) and Boolean Formula:

Example:

add r3,r4 ; Add r4 to r3

brvc noover ; Branch if no overflow

...

noover: nop ; Branch destination (do nothing)

Words: 1 (2 bytes)

Cycles: 1 if condition is false

2 if condition is true

1111 01kk kkkk k011

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44 AVR Instruction Set

0856E–AVR–11/05

BRVS – Branch if Overflow Set

Description:

Conditional relative branch. Tests the Overflow Flag (V) and branches relatively to PC if V is set. This instruction branches

relatively to PC in either direction (PC - 63 ≤ destination ≤ PC + 64). The parameter k is the offset from PC and is repre-

sented in two’s complement form. (Equivalent to instruction BRBS 3,k).

Operation:

(i) If V = 1 then PC ← PC + k + 1, else PC ← PC + 1

Syntax: Operands: Program Counter:

(i) BRVS k -64 ≤ k ≤ +63 PC ← PC + k + 1

PC ← PC + 1, if condition is false

16-bit Opcode:

Status Register (SREG) and Boolean Formula:

Example:

add r3,r4 ; Add r4 to r3

brvs overfl ; Branch if overflow

...

overfl: nop ; Branch destination (do nothing)

Words: 1 (2 bytes)

Cycles: 1 if condition is false

2 if condition is true

1111 00kk kkkk k011

ITHSVNZC

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AVR Instruction Set

0856E–AVR–11/05

BSET – Bit Set in SREG

Description:

Sets a single Flag or bit in SREG.

Operation:

(i) SREG(s) ← 1

Syntax: Operands: Program Counter:

(i) BSET s 0 ≤ s ≤ 7PC ← PC + 1

16-bit Opcode:

Status Register (SREG) and Boolean Formula:

I: 1 if s = 7; Unchanged otherwise.

T: 1 if s = 6; Unchanged otherwise.

H: 1 if s = 5; Unchanged otherwise.

S: 1 if s = 4; Unchanged otherwise.

V: 1 if s = 3; Unchanged otherwise.

N: 1 if s = 2; Unchanged otherwise.

Z: 1 if s = 1; Unchanged otherwise.

C: 1 if s = 0; Unchanged otherwise.

Example:

bset 6 ; Set T Flag

bset 7 ; Enable interrupt

Words: 1 (2 bytes)

Cycles: 1

1001 0100 0sss 1000

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46 AVR Instruction Set

0856E–AVR–11/05

BST – Bit Store from Bit in Register to T Flag in SREG

Description:

Stores bit b from Rd to the T Flag in SREG (Status Register).

Operation:

(i) T ← Rd(b)

Syntax: Operands: Program Counter:

(i) BST Rd,b 0 ≤ d ≤ 31, 0 ≤ b ≤ 7PC ← PC + 1

16-bit Opcode:

Status Register (SREG) and Boolean Formula:

T: 0 if bit b in Rd is cleared. Set to 1 otherwise.

Example:

; Copy bit

bst r1,2 ; Store bit 2 of r1 in T Flag

bld r0,4 ; Load T into bit 4 of r0

Words: 1 (2 bytes)

Cycles: 1

1111 101d dddd 0bbb

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AVR Instruction Set

0856E–AVR–11/05

CALL – Long Call to a Subroutine

Description:

Calls to a subroutine within the entire Program memory. The return address (to the instruction after the CALL) will be stored

onto the Stack. (See also RCALL). The Stack Pointer uses a post-decrement scheme during CALL.

This instruction is not available in all devices. Refer to the device specific instruction set summary.

Operation:

(i) PC ← k Devices with 16 bits PC, 128K bytes Program memory maximum.

(ii) PC ← k Devices with 22 bits PC, 8M bytes Program memory maximum.

Syntax: Operands: Program Counter Stack:

(i) CALL k 0 ≤ k < 64K PC ← kSTACK ← PC+2

SP ← SP-2, (2 bytes, 16 bits)

(ii) CALL k 0 ≤ k < 4M PC ← kSTACK ← PC+2

SP ← SP-3 (3 bytes, 22 bits)

32-bit Opcode:

Status Register (SREG) and Boolean Formula:

Example:

mov r16,r0 ; Copy r0 to r16

call check ; Call subroutine

nop ; Continue (do nothing)

...

check: cpi r16,$42 ; Check if r16 has a special value

breq error ; Branch if equal

ret ; Return from subroutine

...

error: rjmp error ; Infinite loop

Words: 2 (4 bytes)

Cycles: 4, devices with 16 bit PC

5, devices with 22 bit PC

1001 010k kkkk 111k

kkkk kkkk kkkk kkkk

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CBI – Clear Bit in I/O Register

Description:

Clears a specified bit in an I/O Register. This instruction operates on the lower 32 I/O Registers – addresses 0-31.

Operation:

(i) I/O(A,b) ← 0

Syntax: Operands: Program Counter:

(i) CBI A,b 0 ≤ A ≤ 31, 0 ≤ b ≤ 7PC ← PC + 1

16-bit Opcode:

Status Register (SREG) and Boolean Formula:

Example:

cbi $12,7 ; Clear bit 7 in Port D

Words: 1 (2 bytes)

Cycles: 2

1001 1000 AAAA Abbb

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AVR Instruction Set

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CBR – Clear Bits in Register

Description:

Clears the specified bits in register Rd. Performs the logical AND between the contents of register Rd and the complement

of the constant mask K. The result will be placed in register Rd.

Operation:

(i) Rd ← Rd • ($FF - K)

Syntax: Operands: Program Counter:

(i) CBR Rd,K 16 ≤ d ≤ 31, 0 ≤ K ≤ 255 PC ← PC + 1

16-bit Opcode: (see ANDI with K complemented)

Status Register (SREG) and Boolean Formula:

S: N ⊕ V, For signed tests.

V: 0

Cleared

N: R7

Set if MSB of the result is set; cleared otherwise.

Z: R7 •R6 •R5• R4• R3 •R2• R1• R0

Set if the result is $00; cleared otherwise.

R (Result) equals Rd after the operation.

Example:

cbr r16,$F0 ; Clear upper nibble of r16

cbr r18,1 ; Clear bit 0 in r18

Words: 1 (2 bytes)

Cycles: 1

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50 AVR Instruction Set

0856E–AVR–11/05

CLC – Clear Carry Flag

Description:

Clears the Carry Flag (C) in SREG (Status Register).

Operation:

(i) C ← 0

Syntax: Operands: Program Counter:

(i) CLC None PC ← PC + 1

16-bit Opcode:

Status Register (SREG) and Boolean Formula:

C: 0

Carry Flag cleared

Example:

add r0,r0 ; Add r0 to itself

clc ; Clear Carry Flag

Words: 1 (2 bytes)

Cycles: 1

1001 0100 1000 1000

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AVR Instruction Set

0856E–AVR–11/05

CLH – Clear Half Carry Flag

Description:

Clears the Half Carry Flag (H) in SREG (Status Register).

Operation:

(i) H ← 0

Syntax: Operands: Program Counter:

(i) CLH None PC ← PC + 1

16-bit Opcode:

Status Register (SREG) and Boolean Formula:

H: 0

Half Carry Flag cleared

Example:

clh ; Clear the Half Carry Flag

Words: 1 (2 bytes)

Cycles: 1

1001 0100 1101 1000

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CLI – Clear Global Interrupt Flag

Description:

Clears the Global Interrupt Flag (I) in SREG (Status Register). The interrupts will be immediately disabled. No interrupt will

be executed after the CLI instruction, even if it occurs simultaneously with the CLI instruction.

Operation:

(i) I ← 0

Syntax: Operands: Program Counter:

(i) CLI None PC ← PC + 1

16-bit Opcode:

Status Register (SREG) and Boolean Formula:

I: 0

Global Interrupt Flag cleared

Example:

in temp, SREG ; Store SREG value (temp must be defined by user)

cli ; Disable interrupts during timed sequence

sbi EECR, EEMWE ; Start EEPROM write

sbi EECR, EEWE

out SREG, temp ; Restore SREG value (I-Flag)

Words: 1 (2 bytes)

Cycles: 1

1001 0100 1111 1000

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AVR Instruction Set

0856E–AVR–11/05

CLN – Clear Negative Flag

Description:

Clears the Negative Flag (N) in SREG (Status Register).

Operation:

(i) N ← 0

Syntax: Operands: Program Counter:

(i) CLN None PC ← PC + 1

16-bit Opcode:

Status Register (SREG) and Boolean Formula:

N: 0

Negative Flag cleared

Example:

add r2,r3 ; Add r3 to r2

cln ; Clear Negative Flag

Words: 1 (2 bytes)

Cycles: 1

1001 0100 1010 1000

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54 AVR Instruction Set

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CLR – Clear Register

Description:

Clears a register. This instruction performs an Exclusive OR between a register and itself. This will clear all bits in the

Operation:

(i) Rd ← Rd ⊕ Rd

Syntax: Operands: Program Counter:

(i) CLR Rd 0 ≤ d ≤ 31 PC ← PC + 1

16-bit Opcode: (see EOR Rd,Rd)

Status Register (SREG) and Boolean Formula:

S: 0

Cleared

V: 0

Cleared

N: 0

Cleared

Z: 1

Set

R (Result) equals Rd after the operation.

Example:

clr r18 ; clear r18

loop: inc r18 ; increase r18

...

cpi r18,$50 ; Compare r18 to $50

brne loop

Words: 1 (2 bytes)

Cycles: 1

0010 01dd dddd dddd

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AVR Instruction Set

0856E–AVR–11/05

CLS – Clear Signed Flag

Description:

Clears the Signed Flag (S) in SREG (Status Register).

Operation:

(i) S ← 0

Syntax: Operands: Program Counter:

(i) CLS None PC ← PC + 1

16-bit Opcode:

Status Register (SREG) and Boolean Formula:

S: 0

Signed Flag cleared

Example:

add r2,r3 ; Add r3 to r2

cls ; Clear Signed Flag

Words: 1 (2 bytes)

Cycles: 1

1001 0100 1100 1000

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CLT – Clear T Flag

Description:

Clears the T Flag in SREG (Status Register).

Operation:

(i) T ← 0

Syntax: Operands: Program Counter:

(i) CLT None PC ← PC + 1

16-bit Opcode:

Status Register (SREG) and Boolean Formula:

T: 0

T Flag cleared

Example:

clt ; Clear T Flag

Words: 1 (2 bytes)

Cycles: 1

1001 0100 1110 1000

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AVR Instruction Set

0856E–AVR–11/05

CLV – Clear Overflow Flag

Description:

Clears the Overflow Flag (V) in SREG (Status Register).

Operation:

(i) V ← 0

Syntax: Operands: Program Counter:

(i) CLV None PC ← PC + 1

16-bit Opcode:

Status Register (SREG) and Boolean Formula:

V: 0

Overflow Flag cleared

Example:

add r2,r3 ; Add r3 to r2

clv ; Clear Overflow Flag

Words: 1 (2 bytes)

Cycles: 1

1001 0100 1011 1000

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58 AVR Instruction Set

0856E–AVR–11/05

CLZ – Clear Zero Flag

Description:

Clears the Zero Flag (Z) in SREG (Status Register).

Operation:

(i) Z ← 0

Syntax: Operands: Program Counter:

(i) CLZ None PC ← PC + 1

16-bit Opcode:

Status Register (SREG) and Boolean Formula:

Z: 0

Zero Flag cleared

Example:

add r2,r3 ; Add r3 to r2

clz ; Clear zero

Words: 1 (2 bytes)

Cycles: 1

1001 0100 1001 1000

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AVR Instruction Set

0856E–AVR–11/05

COM – One’s Complement

Description:

This instruction performs a One’s Complement of register Rd.

Operation:

(i) Rd ← $FF - Rd

Syntax: Operands: Program Counter:

(i) COM Rd 0 ≤ d ≤ 31 PC ← PC + 1

16-bit Opcode:

Status Register (SREG) and Boolean Formula:

S: N ⊕ V

For signed tests.

V: 0

Cleared.

N: R7

Set if MSB of the result is set; cleared otherwise.

Z: R7 •R6• R5• R4 •R3 •R2• R1 •R0

Set if the result is $00; Cleared otherwise.

C: 1

Set.

R (Result) equals Rd after the operation.

Example:

com r4 ; Take one’s complement of r4

breq zero ; Branch if zero

...

zero: nop ; Branch destination (do nothing)

Words: 1 (2 bytes)

Cycles: 1

1001 010d dddd 0000

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60 AVR Instruction Set

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CP – Compare

Description:

This instruction performs a compare between two registers Rd and Rr. None of the registers are changed. All conditional

branches can be used after this instruction.

Operation:

(i) Rd - Rr

Syntax: Operands: Program Counter:

(i) CP Rd,Rr 0 ≤ d ≤ 31, 0 ≤ r ≤ 31 PC ← PC + 1

16-bit Opcode:

Status Register (SREG) and Boolean Formula:

H: Rd3 •Rr3+ Rr3 •R3 +R3• Rd3

Set if there was a borrow from bit 3; cleared otherwise

S: N ⊕ V, For signed tests.

V: Rd7• Rr7 •R7+ Rd7 •Rr7 •R7

Set if two’s complement overflow resulted from the operation; cleared otherwise.

N: R7

Set if MSB of the result is set; cleared otherwise.

Z: R7• R6 •R5• R4 •R3 •R2 •R1 •R0

Set if the result is $00; cleared otherwise.

C: Rd7 •Rr7+ Rr7• R7 +R7• Rd7

Set if the absolute value of the contents of Rr is larger than the absolute value of Rd; cleared otherwise.

R (Result) after the operation.

Example:

cp r4,r19 ; Compare r4 with r19

brne noteq ; Branch if r4 <> r19

...

noteq: nop ; Branch destination (do nothing)

Words: 1 (2 bytes)

Cycles: 1

0001 01rd dddd rrrr

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AVR Instruction Set

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CPC – Compare with Carry

Description:

This instruction performs a compare between two registers Rd and Rr and also takes into account the previous carry. None

of the registers are changed. All conditional branches can be used after this instruction.

Operation:

(i) Rd - Rr - C

Syntax: Operands: Program Counter:

(i) CPC Rd,Rr 0 ≤ d ≤ 31, 0 ≤ r ≤ 31 PC ← PC + 1

16-bit Opcode:

Status Register (SREG) and Boolean Formula:

H: Rd3 •Rr3+ Rr3 •R3 +R3 •Rd3

Set if there was a borrow from bit 3; cleared otherwise

S: N ⊕ V, For signed tests.

V: Rd7 •Rr7• R7+ Rd7• Rr7 •R7

Set if two’s complement overflow resulted from the operation; cleared otherwise.

N: R7

Set if MSB of the result is set; cleared otherwise.

Z: R7 •R6• R5• R4 •R3 •R2 •R1• R0 •Z

Previous value remains unchanged when the result is zero; cleared otherwise.

C: Rd7 •Rr7+ Rr7• R7 +R7 •Rd7

Set if the absolute value of the contents of Rr plus previous carry is larger than the absolute value of Rd; cleared

otherwise.

R (Result) after the operation.

Example:

; Compare r3:r2 with r1:r0

cp r2,r0 ; Compare low byte

cpc r3,r1 ; Compare high byte

brne noteq ; Branch if not equal

...

noteq: nop ; Branch destination (do nothing)

0000 01rd dddd rrrr

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62 AVR Instruction Set

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Words: 1 (2 bytes)

Cycles: 1

AVR Instruction Set

0856E–AVR–11/05

CPI – Compare with Immediate

Description:

This instruction performs a compare between register Rd and a constant. The register is not changed. All conditional

branches can be used after this instruction.

Operation:

(i) Rd - K

Syntax: Operands: Program Counter:

(i) CPI Rd,K 16 ≤ d ≤ 31, 0≤ K ≤ 255 PC ← PC + 1

16-bit Opcode:

Status Register (SREG) and Boolean Formula:

H: Rd3 •K3+ K3• R3+ R3 •Rd3

Set if there was a borrow from bit 3; cleared otherwise

S: N ⊕ V, For signed tests.

V: Rd7 •K7 •R7 +Rd7 •K7 •R7

Set if two’s complement overflow resulted from the operation; cleared otherwise.

N: R7

Set if MSB of the result is set; cleared otherwise.

Z: R7 •R6• R5 •R4• R3• R2 •R1 •R0

Set if the result is $00; cleared otherwise.

C: Rd7 •K7 +K7 •R7+ R7 •Rd7

Set if the absolute value of K is larger than the absolute value of Rd; cleared otherwise.

R (Result) after the operation.

Example:

cpi r19,3 ; Compare r19 with 3

brne error ; Branch if r19<>3

...

error: nop ; Branch destination (do nothing)

Words: 1 (2 bytes)

Cycles: 1

0011 KKKK dddd KKKK

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64 AVR Instruction Set

0856E–AVR–11/05

CPSE – Compare Skip if Equal

Description:

This instruction performs a compare between two registers Rd and Rr, and skips the next instruction if Rd = Rr.

Operation:

(i) If Rd = Rr then PC ← PC + 2 (or 3) else PC ← PC + 1

Syntax: Operands: Program Counter:

(i) CPSE Rd,Rr 0 ≤ d ≤ 31, 0 ≤ r ≤ 31 PC ← PC + 1, Condition false - no skip

PC ← PC + 2, Skip a one word instruction

PC ← PC + 3, Skip a two word instruction

16-bit Opcode:

Status Register (SREG) and Boolean Formula:

Example:

inc r4 ; Increase r4

cpse r4,r0 ; Compare r4 to r0

neg r4 ; Only executed if r4<>r0

nop ; Continue (do nothing)

Words: 1 (2 bytes)

Cycles: 1 if condition is false (no skip)

2 if condition is true (skip is executed) and the instruction skipped is 1 word

3 if condition is true (skip is executed) and the instruction skipped is 2 words

0001 00rd dddd rrrr

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AVR Instruction Set

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DEC – Decrement

Description:

Subtracts one -1- from the contents of register Rd and places the result in the destination register Rd.

The C Flag in SREG is not affected by the operation, thus allowing the DEC instruction to be used on a loop counter in mul-

tiple-precision computations.

When operating on unsigned values, only BREQ and BRNE branches can be expected to perform consistently. When

operating on two’s complement values, all signed branches are available.

Operation:

(i) Rd ← Rd - 1

Syntax: Operands: Program Counter:

(i) DEC Rd 0 ≤ d ≤ 31 PC ← PC + 1

16-bit Opcode:

Status Register and Boolean Formula:

S: N ⊕ V

For signed tests.

V: R7 •R6 •R5 •R4• R3• R2 •R1• R0

Set if two’s complement overflow resulted from the operation; cleared otherwise. Two’s complement overflow occurs

if and only if Rd was $80 before the operation.

N: R7

Set if MSB of the result is set; cleared otherwise.

Z: R7 •R6• R5 •R4• R3• R2• R1• R0

Set if the result is $00; Cleared otherwise.

R (Result) equals Rd after the operation.

Example:

ldi r17,$10 ; Load constant in r17

loop: add r1,r2 ; Add r2 to r1

dec r17 ; Decrement r17

brne loop ; Branch if r17<>0

nop ; Continue (do nothing)

Words: 1 (2 bytes)

Cycles: 1

1001 010d dddd 1010

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66 AVR Instruction Set

0856E–AVR–11/05

EICALL – Extended Indirect Call to Subroutine

Description:

Indirect call of a subroutine pointed to by the Z (16 bits) Pointer Register in the Register File and the EIND Register in the

I/O space. This instruction allows for indirect calls to the entire 4M (words) Program memory space. See also ICALL. The

Stack Pointer uses a post-decrement scheme during EICALL.

This instruction is not available in all devices. Refer to the device specific instruction set summary.

Operation:

(i) PC(15:0) ← Z(15:0)

PC(21:16) ← EIND

Syntax: Operands: Program Counter: Stack:

(i) EICALL None See Operation STACK ← PC + 1

SP ← SP - 3 (3 bytes, 22 bits)

16-bit Opcode:

Status Register (SREG) and Boolean Formula:

Example:

ldi r16,$05 ; Set up EIND and Z-pointer

out EIND,r16

ldi r30,$00

ldi r31,$10

eicall ; Call to $051000

Words: 1 (2 bytes)

Cycles: 4 (only implemented in devices with 22 bit PC)

1001 0101 0001 1001

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AVR Instruction Set

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EIJMP – Extended Indirect Jump

Description:

Indirect jump to the address pointed to by the Z (16 bits) Pointer Register in the Register File and the EIND Register in the

I/O space. This instruction allows for indirect jumps to the entire 4M (words) Program memory space. See also IJMP.

This instruction is not available in all devices. Refer to the device specific instruction set summary.

Operation:

(i) PC(15:0) ← Z(15:0)

PC(21:16) ← EIND

Syntax: Operands: Program Counter: Stack:

(i) EIJMP None See Operation Not Affected

16-bit Opcode:

Status Register (SREG) and Boolean Formula:

Example:

ldi r16,$05 ; Set up EIND and Z-pointer

out EIND,r16

ldi r30,$00

ldi r31,$10

eijmp ; Jump to $051000

Words: 1 (2 bytes)

Cycles: 2

1001 0100 0001 1001

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68 AVR Instruction Set

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ELPM – Extended Load Program Memory

Description:

Loads one byte pointed to by the Z-register and the RAMPZ Register in the I/O space, and places this byte in the destina-

tion register Rd. This instruction features a 100% space effective constant initialization or constant data fetch. The Program

memory is organized in 16-bit words while the Z-pointer is a byte address. Thus, the least significant bit of the Z-pointer

selects either low byte (ZLSB = 0) or high byte (ZLSB = 1). This instruction can address the entire Program memory space.

The Z-pointer Register can either be left unchanged by the operation, or it can be incremented. The incrementation applies

to the entire 24-bit concatenation of the RAMPZ and Z-pointer Registers.

Devices with Self-Programming capability can use the ELPM instruction to read the Fuse and Lock bit value. Refer to the

device documentation for a detailed description.

This instruction is not available in all devices. Refer to the device specific instruction set summary.

The result of these combinations is undefined:

ELPM r30, Z+

ELPM r31, Z+

Operation: Comment:

(i) R0 ← (RAMPZ:Z) RAMPZ:Z: Unchanged, R0 implied destination register

(ii) Rd ← (RAMPZ:Z) RAMPZ:Z: Unchanged

(iii) Rd ← (RAMPZ:Z) (RAMPZ:Z) ← (RAMPZ:Z) + 1 RAMPZ:Z: Post incremented

Syntax: Operands: Program Counter:

(i) ELPM None, R0 implied PC ← PC + 1

(ii) ELPM Rd, Z 0 ≤ d ≤ 31 PC ← PC + 1

(iii) ELPM Rd, Z+ 0 ≤ d ≤ 31 PC ← PC + 1

16 bit Opcode:

Status Register (SREG) and Boolean Formula:

Example:

ldi ZL, byte3(Table_1<<1); Initialize Z-pointer

out RAMPZ, ZL

ldi ZH, byte2(Table_1<<1)

ldi ZL, byte1(Table_1<<1)

elpm r16, Z+ ; Load constant from Program

; memory pointed to by RAMPZ:Z (Z is r31:r30)

...

Table_1:

.dw 0x3738 ; 0x38 is addressed when ZLSB = 0

; 0x37 is addressed when ZLSB = 1

(i) 1001 0101 1101 1000

(ii) 1001 000d dddd 0110

(iii) 1001 000d dddd 0111

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...

Words: 1 (2 bytes)

Cycles: 3

70 AVR Instruction Set

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EOR – Exclusive OR

Description:

Performs the logical EOR between the contents of register Rd and register Rr and places the result in the destination regis-

ter Rd.

Operation:

(i) Rd ← Rd ⊕ Rr

Syntax: Operands: Program Counter:

(i) EOR Rd,Rr 0 ≤ d ≤ 31, 0 ≤ r ≤ 31 PC ← PC + 1

16-bit Opcode:

Status Register (SREG) and Boolean Formula:

S: N ⊕ V, For signed tests.

V: 0

Cleared

N: R7

Set if MSB of the result is set; cleared otherwise.

Z: R7 •R6 •R5 •R4• R3• R2 •R1• R0

Set if the result is $00; cleared otherwise.

R (Result) equals Rd after the operation.

Example:

eor r4,r4 ; Clear r4

eor r0,r22 ; Bitwise exclusive or between r0 and r22

Words: 1 (2 bytes)

Cycles: 1

0010 01rd dddd rrrr

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AVR Instruction Set

0856E–AVR–11/05

FMUL – Fractional Multiply Unsigned

Description:

This instruction performs 8-bit × 8-bit → 16-bit unsigned multiplication and shifts the result one bit left.

Let (N.Q) denote a fractional number with N binary digits left of the radix point, and Q binary digits right of the radix point. A

multiplication between two numbers in the formats (N1.Q1) and (N2.Q2) results in the format ((N1+N2).(Q1+Q2)). For sig-

nal processing applications, the format (1.7) is widely used for the inputs, resulting in a (2.14) format for the product. A left

shift is required for the high byte of the product to be in the same format as the inputs. The FMUL instruction incorporates

the shift operation in the same number of cycles as MUL.

The (1.7) format is most commonly used with signed numbers, while FMUL performs an unsigned multiplication. This

instruction is therefore most useful for calculating one of the partial products when performing a signed multiplication with

16-bit inputs in the (1.15) format, yielding a result in the (1.31) format. Note: the result of the FMUL operation may suffer

from a 2’s complement overflow if interpreted as a number in the (1.15) format. The MSB of the multiplication before shift-

ing must be taken into account, and is found in the carry bit. See the following example.

The multiplicand Rd and the multiplier Rr are two registers containing unsigned fractional numbers where the implicit radix

point lies between bit 6 and bit 7. The 16-bit unsigned fractional product with the implicit radix point between bit 14 and bit

15 is placed in R1 (high byte) and R0 (low byte).

This instruction is not available in all devices. Refer to the device specific instruction set summary.

Operation:

(i) R1:R0 ← Rd × Rr (unsigned (1.15) ← unsigned (1.7) × unsigned (1.7))

Syntax: Operands: Program Counter:

(i) FMUL Rd,Rr 16 ≤ d ≤ 23, 16≤ r ≤ 23 PC ← PC + 1

16-bit Opcode:

Status Register (SREG) and Boolean Formula:

C: R16

Set if bit 15 of the result before left shift is set; cleared otherwise.

Z: R15 •R14 •R13 •R12 •R11 •R10 •R9 •R8 •R7• R6• R5• R4• R3• R2 •R1• R0

Set if the result is $0000; cleared otherwise.

R (Result) equals R1,R0 after the operation.

Rd Rr R1 R0

Multiplicand ×Multiplier Æ Product High Product Low

88 16

0000 0011 0ddd 1rrr

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72 AVR Instruction Set

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Example:

;******************************************************************************

;* DESCRIPTION

;*Signed fractional multiply of two 16-bit numbers with 32-bit result.

;* USAGE

;*r19:r18:r17:r16 = ( r23:r22 * r21:r20 ) << 1

;******************************************************************************

fmuls16x16_32:

clrr2

fmulsr23, r21;((signed)ah * (signed)bh) << 1

movwr19:r18, r1:r0

fmulr22, r20;(al * bl) << 1

adcr18, r2

movwr17:r16, r1:r0

fmulsur23, r20;((signed)ah * bl) << 1

sbcr19, r2

addr17, r0

adcr18, r1

adcr19, r2

fmulsur21, r22;((signed)bh * al) << 1

sbcr19, r2

addr17, r0

adcr18, r1

adcr19, r2

Words: 1 (2 bytes)

Cycles: 2

AVR Instruction Set

0856E–AVR–11/05

FMULS – Fractional Multiply Signed

Description:

This instruction performs 8-bit × 8-bit → 16-bit signed multiplication and shifts the result one bit left.

Let (N.Q) denote a fractional number with N binary digits left of the radix point, and Q binary digits right of the radix point. A

multiplication between two numbers in the formats (N1.Q1) and (N2.Q2) results in the format ((N1+N2).(Q1+Q2)). For sig-

nal processing applications, the format (1.7) is widely used for the inputs, resulting in a (2.14) format for the product. A left

shift is required for the high byte of the product to be in the same format as the inputs. The FMULS instruction incorporates

the shift operation in the same number of cycles as MULS.

The multiplicand Rd and the multiplier Rr are two registers containing signed fractional numbers where the implicit radix

point lies between bit 6 and bit 7. The 16-bit signed fractional product with the implicit radix point between bit 14 and bit 15

is placed in R1 (high byte) and R0 (low byte).

Note that when multiplying 0x80 (-1) with 0x80 (-1), the result of the shift operation is 0x8000 (-1). The shift operation thus

gives a two’s complement overflow. This must be checked and handled by software.

This instruction is not available in all devices. Refer to the device specific instruction set summary.

Operation:

(i) R1:R0 ← Rd × Rr (signed (1.15) ← signed (1.7) × signed (1.7))

Syntax: Operands: Program Counter:

(i) FMULS Rd,Rr 16 ≤ d ≤ 23, 16≤ r ≤ 23 PC ← PC + 1

16-bit Opcode:

Status Register (SREG) and Boolean Formula:

C: R16

Set if bit 15 of the result before left shift is set; cleared otherwise.

Z: R15 •R14 •R13 •R12 •R11 •R10 •R9 •R8 •R7• R6• R5• R4• R3• R2 •R1• R0

Set if the result is $0000; cleared otherwise.

R (Result) equals R1,R0 after the operation.

Example:

fmuls r23,r22 ; Multiply signed r23 and r22 in (1.7) format, result in (1.15) format

movw r23:r22,r1:r0 ; Copy result back in r23:r22

Rd Rr R1 R0

Multiplicand ×Multiplier →Product High Product Low

88 16

0000 0011 1ddd 0rrr

ITHSVNZC

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⇔⇔

74 AVR Instruction Set

0856E–AVR–11/05

Words: 1 (2 bytes)

Cycles: 2

AVR Instruction Set

0856E–AVR–11/05

FMULSU – Fractional Multiply Signed with Unsigned

Description:

This instruction performs 8-bit × 8-bit → 16-bit signed multiplication and shifts the result one bit left.

Let (N.Q) denote a fractional number with N binary digits left of the radix point, and Q binary digits right of the radix point. A

multiplication between two numbers in the formats (N1.Q1) and (N2.Q2) results in the format ((N1+N2).(Q1+Q2)). For sig-

nal processing applications, the format (1.7) is widely used for the inputs, resulting in a (2.14) format for the product. A left

shift is required for the high byte of the product to be in the same format as the inputs. The FMULSU instruction incorpo-

rates the shift operation in the same number of cycles as MULSU.

The (1.7) format is most commonly used with signed numbers, while FMULSU performs a multiplication with one unsigned

and one signed input. This instruction is therefore most useful for calculating two of the partial products when performing a

signed multiplication with 16-bit inputs in the (1.15) format, yielding a result in the (1.31) format. Note: the result of the

FMULSU operation may suffer from a 2's complement overflow if interpreted as a number in the (1.15) format. The MSB of

the multiplication before shifting must be taken into account, and is found in the carry bit. See the following example.

The multiplicand Rd and the multiplier Rr are two registers containing fractional numbers where the implicit radix point lies

between bit 6 and bit 7. The multiplicand Rd is a signed fractional number, and the multiplier Rr is an unsigned fractional

number. The 16-bit signed fractional product with the implicit radix point between bit 14 and bit 15 is placed in R1 (high

byte) and R0 (low byte).

This instruction is not available in all devices. Refer to the device specific instruction set summary.

Operation:

(i) R1:R0 ← Rd × Rr (signed (1.15) ← signed (1.7) × unsigned (1.7))

Syntax: Operands: Program Counter:

(i) FMULSU Rd,Rr 16 ≤ d ≤ 23, 16≤ r ≤ 23 PC ← PC + 1

16-bit Opcode:

Status Register (SREG) and Boolean Formula:

C: R16

Set if bit 15 of the result before left shift is set; cleared otherwise.

Z: R15 •R14 •R13 •R12 •R11 •R10 •R9 •R8 •R7• R6• R5• R4• R3• R2 •R1• R0

Set if the result is $0000; cleared otherwise.

R (Result) equals R1,R0 after the operation.

Rd Rr R1 R0

Multiplicand ×Multiplier →Product High Product Low

88 16

0000 0011 1ddd 1rrr

ITHSVNZC

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76 AVR Instruction Set

0856E–AVR–11/05

Example:

;******************************************************************************

;* DESCRIPTION

;*Signed fractional multiply of two 16-bit numbers with 32-bit result.

;* USAGE

;*r19:r18:r17:r16 = ( r23:r22 * r21:r20 ) << 1

;******************************************************************************

fmuls16x16_32:

clrr2

fmulsr23, r21;((signed)ah * (signed)bh) << 1

movwr19:r18, r1:r0

fmulr22, r20;(al * bl) << 1

adcr18, r2

movwr17:r16, r1:r0

fmulsur23, r20;((signed)ah * bl) << 1

sbcr19, r2

addr17, r0

adcr18, r1

adcr19, r2

fmulsur21, r22;((signed)bh * al) << 1

sbcr19, r2

addr17, r0

adcr18, r1

adcr19, r2

Words: 1 (2 bytes)

Cycles: 2

AVR Instruction Set

0856E–AVR–11/05

ICALL – Indirect Call to Subroutine

Description:

Calls to a subroutine within the entire 4M (words) Program memory. The return address (to the instruction after the CALL)

will be stored onto the Stack. See also RCALL. The Stack Pointer uses a post-decrement scheme during CALL.

This instruction is not available in all devices. Refer to the device specific instruction set summary.

Operation:

(i) PC(15:0) ← Z(15:0) Devices with 16 bits PC, 128K bytes Program memory maximum.

(ii) PC(15:0) ← Z(15:0) Devices with 22 bits PC, 8M bytes Program memory maximum.

PC(21:16) ← 0

Syntax: Operands: Program Counter: Stack:

(i) ICALL None See Operation STACK ← PC + 1

SP ← SP - 2 (2 bytes, 16 bits)

(ii) ICALL None See Operation STACK ← PC + 1

SP ← SP - 3 (3 bytes, 22 bits)

16-bit Opcode:

Status Register (SREG) and Boolean Formula:

Example:

mov r30,r0 ; Set offset to call table

icall ; Call routine pointed to by r31:r30

Words: 1 (2 bytes)

Cycles: 3 devices with 16 bit PC

4 devices with 22 bit PC

1001 0101 0000 1001

ITHSVNZC

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78 AVR Instruction Set

0856E–AVR–11/05

IJMP – Indirect Jump

Description:

Indirect jump to the address pointed to by the Z (16 bits) Pointer Register in the Register File. The Z-pointer Register is 16

bits wide and allows jump within the lowest 64K words (128K bytes) section of Program memory.

This instruction is not available in all devices. Refer to the device specific instruction set summary.

Operation:

(i) PC ← Z(15:0) Devices with 16 bits PC, 128K bytes Program memory maximum.

(ii) PC(15:0) ← Z(15:0) Devices with 22 bits PC, 8M bytes Program memory maximum.

PC(21:16) ← 0

Syntax: Operands: Program Counter: Stack:

(i),(ii) IJMP None See Operation Not Affected

16-bit Opcode:

Status Register (SREG) and Boolean Formula:

Example:

mov r30,r0 ; Set offset to jump table

ijmp ; Jump to routine pointed to by r31:r30

Words: 1 (2 bytes)

Cycles: 2

1001 0100 0000 1001

ITHSVNZC

––––––––

AVR Instruction Set

0856E–AVR–11/05

IN - Load an I/O Location to Register

Description:

Loads data from the I/O Space (Ports, Timers, Configuration Registers etc.) into register Rd in the Register File.

Operation:

(i) Rd ← I/O(A)

Syntax: Operands: Program Counter:

(i) IN Rd,A 0 ≤ d ≤ 31, 0 ≤ A ≤ 63 PC ← PC + 1

16-bit Opcode:

Status Register (SREG) and Boolean Formula:

Example:

in r25,$16 ; Read Port B

cpi r25,4 ; Compare read value to constant

breq exit ; Branch if r25=4

...

exit: nop ; Branch destination (do nothing)

Words: 1 (2 bytes)

Cycles: 1

1011 0AAd dddd AAAA

ITHSVNZC

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80 AVR Instruction Set

0856E–AVR–11/05

INC – Increment

Description:

Adds one -1- to the contents of register Rd and places the result in the destination register Rd.

The C Flag in SREG is not affected by the operation, thus allowing the INC instruction to be used on a loop counter in mul-

tiple-precision computations.

When operating on unsigned numbers, only BREQ and BRNE branches can be expected to perform consistently. When

operating on two’s complement values, all signed branches are available.

Operation:

(i) Rd ← Rd + 1

Syntax: Operands: Program Counter:

(i) INC Rd 0 ≤ d ≤ 31 PC ← PC + 1

16-bit Opcode:

Status Register and Boolean Formula:

S: N ⊕ V

For signed tests.

V: R7 •R6 •R5 •R4 •R3• R2 •R1 •R0

Set if two’s complement overflow resulted from the operation; cleared otherwise. Two’s complement overflow occurs

if and only if Rd was $7F before the operation.

N: R7

Set if MSB of the result is set; cleared otherwise.

Z: R7 •R6 •R5 •R4•R3 •R2• R1• R0

Set if the result is $00; Cleared otherwise.

R (Result) equals Rd after the operation.

Example:

clr r22 ; clear r22

loop: inc r22 ; increment r22

...

cpi r22,$4F ; Compare r22 to $4f

brne loop ; Branch if not equal

nop ; Continue (do nothing)

1001 010d dddd 0011

ITHSVNZC

–– –⇔⇔⇔⇔ –

AVR Instruction Set

0856E–AVR–11/05

Words: 1 (2 bytes)

Cycles: 1

82 AVR Instruction Set

0856E–AVR–11/05

JMP – Jump

Description:

Jump to an address within the entire 4M (words) Program memory. See also RJMP.

This instruction is not available in all devices. Refer to the device specific instruction set summary.

Operation:

(i) PC ← k

Syntax: Operands: Program Counter: Stack:

(i) JMP k 0 ≤ k < 4M PC ← k Unchanged

32-bit Opcode:

Status Register (SREG) and Boolean Formula:

Example:

mov r1,r0 ; Copy r0 to r1

jmp farplc ; Unconditional jump

...

farplc: nop ; Jump destination (do nothing)

Words: 2 (4 bytes)

Cycles: 3

1001 010k kkkk 110k

kkkk kkkk kkkk kkkk

ITHSVNZC

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AVR Instruction Set

0856E–AVR–11/05

LD – Load Indirect from Data Space to Register using Index X

Description:

Loads one byte indirect from the data space to a register. For parts with SRAM, the data space consists of the Register

File, I/O memory and internal SRAM (and external SRAM if applicable). For parts without SRAM, the data space consists of

the Register File only. The EEPROM has a separate address space.

The data location is pointed to by the X (16 bits) Pointer Register in the Register File. Memory access is limited to the cur-

rent data segment of 64K bytes. To access another data segment in devices with more than 64K bytes data space, the

RAMPX in register in the I/O area has to be changed.

The X-pointer Register can either be left unchanged by the operation, or it can be post-incremented or pre-decremented.

These features are especially suited for accessing arrays, tables, and Stack Pointer usage of the X-pointer Register. Note

that only the low byte of the X-pointer is updated in devices with no more than 256 bytes data space. For such devices, the

high byte of the pointer is not used by this instruction and can be used for other purposes. The RAMPX Register in the I/O

area is updated in parts with more than 64K bytes data space or more than 64K bytes Program memory, and the incre-

ment/decrement is added to the entire 24-bit address on such devices.

Not all variants of this instruction is available in all devices. Refer to the device specific instruction set summary.

The result of these combinations is undefined:

LD r26, X+

LD r27, X+

LD r26, -X

LD r27, -X

Using the X-pointer:

Operation: Comment:

(i) Rd ← (X) X: Unchanged

(ii) Rd ← (X) X ← X + 1 X: Post incremented

(iii) X ← X - 1 Rd ← (X) X: Pre decremented

Syntax: Operands: Program Counter:

(i) LD Rd, X 0 ≤ d ≤ 31 PC ← PC + 1

(ii) LD Rd, X+ 0 ≤ d ≤ 31 PC ← PC + 1

(iii) LD Rd, -X 0 ≤ d ≤ 31 PC ← PC + 1

16-bit Opcode:

Status Register (SREG) and Boolean Formula:

Example:

clr r27 ; Clear X high byte

ldi r26,$60 ; Set X low byte to $60

(i) 1001 000d dddd 1100

(ii) 1001 000d dddd 1101

(iii) 1001 000d dddd 1110

ITHSVNZC

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84 AVR Instruction Set

0856E–AVR–11/05

ld r0,X+ ; Load r0 with data space loc. $60(X post inc)

ld r1,X ; Load r1 with data space loc. $61

ldi r26,$63 ; Set X low byte to $63

ld r2,X ; Load r2 with data space loc. $63

ld r3,–X ; Load r3 with data space loc. $62(X pre dec)

Words: 1 (2 bytes)

Cycles: 2

AVR Instruction Set

0856E–AVR–11/05

LD (LDD) – Load Indirect from Data Space to Register using Index Y

Description:

Loads one byte indirect with or without displacement from the data space to a register. For parts with SRAM, the data

space consists of the Register File, I/O memory and internal SRAM (and external SRAM if applicable). For parts without

SRAM, the data space consists of the Register File only. The EEPROM has a separate address space.

The data location is pointed to by the Y (16 bits) Pointer Register in the Register File. Memory access is limited to the cur-

rent data segment of 64K bytes. To access another data segment in devices with more than 64K bytes data space, the

RAMPY in register in the I/O area has to be changed.

The Y-pointer Register can either be left unchanged by the operation, or it can be post-incremented or pre-decremented.

These features are especially suited for accessing arrays, tables, and Stack Pointer usage of the Y-pointer Register. Note

that only the low byte of the Y-pointer is updated in devices with no more than 256 bytes data space. For such devices, the

high byte of the pointer is not used by this instruction and can be used for other purposes. The RAMPY Register in the I/O

area is updated in parts with more than 64K bytes data space or more than 64K bytes Program memory, and the incre-

ment/decrement/displacement is added to the entire 24-bit address on such devices.

Not all variants of this instruction is available in all devices. Refer to the device specific instruction set summary.

The result of these combinations is undefined:

LD r28, Y+

LD r29, Y+

LD r28, -Y

LD r29, -Y

Using the Y-pointer:

Operation: Comment:

(i) Rd ← (Y) Y: Unchanged

(ii) Rd ← (Y) Y ← Y + 1 Y: Post incremented

(iii) Y ← Y - 1 Rd ← (Y) Y: Pre decremented

(iiii) Rd ← (Y+q) Y: Unchanged, q: Displacement

Syntax: Operands: Program Counter:

(i) LD Rd, Y 0 ≤ d ≤ 31 PC ← PC + 1

(ii) LD Rd, Y+ 0 ≤ d ≤ 31 PC ← PC + 1

(iii) LD Rd, -Y 0 ≤ d ≤ 31 PC ← PC + 1

(iiii) LDD Rd, Y+q 0 ≤ d ≤ 31, 0 ≤ q ≤ 63 PC ← PC + 1

86 AVR Instruction Set

0856E–AVR–11/05

16-bit Opcode:

Status Register (SREG) and Boolean Formula:

Example:

clr r29 ; Clear Y high byte

ldi r28,$60 ; Set Y low byte to $60

ld r0,Y+ ; Load r0 with data space loc. $60(Y post inc)

ld r1,Y ; Load r1 with data space loc. $61

ldi r28,$63 ; Set Y low byte to $63

ld r2,Y ; Load r2 with data space loc. $63

ld r3,-Y ; Load r3 with data space loc. $62(Y pre dec)

ldd r4,Y+2 ; Load r4 with data space loc. $64

Words: 1 (2 bytes)

Cycles: 2

(i) 1000 000d dddd 1000

(ii) 1001 000d dddd 1001

(iii) 1001 000d dddd 1010

(iiii) 10q0 qq0d dddd 1qqq

ITHSVNZC

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AVR Instruction Set

0856E–AVR–11/05

LD (LDD) – Load Indirect From Data Space to Register using Index Z

Description:

Loads one byte indirect with or without displacement from the data space to a register. For parts with SRAM, the data

space consists of the Register File, I/O memory and internal SRAM (and external SRAM if applicable). For parts without

SRAM, the data space consists of the Register File only. The EEPROM has a separate address space.

The data location is pointed to by the Z (16 bits) Pointer Register in the Register File. Memory access is limited to the cur-

rent data segment of 64K bytes. To access another data segment in devices with more than 64K bytes data space, the

RAMPZ in register in the I/O area has to be changed.

The Z-pointer Register can either be left unchanged by the operation, or it can be post-incremented or pre-decremented.

These features are especially suited for Stack Pointer usage of the Z-pointer Register, however because the Z-pointer

Register can be used for indirect subroutine calls, indirect jumps and table lookup, it is often more convenient to use the X

or Y-pointer as a dedicated Stack Pointer. Note that only the low byte of the Z-pointer is updated in devices with no more

than 256 bytes data space. For such devices, the high byte of the pointer is not used by this instruction and can be used for

other purposes. The RAMPZ Register in the I/O area is updated in parts with more than 64K bytes data space or more than

64K bytes Program memory, and the increment/decrement/displacement is added to the entire 24-bit address on such

devices.

Not all variants of this instruction is available in all devices. Refer to the device specific instruction set summary.

For using the Z-pointer for table lookup in Program memory see the LPM and ELPM instructions.

The result of these combinations is undefined:

LD r30, Z+

LD r31, Z+

LD r30, -Z

LD r31, -Z

Using the Z-pointer:

Operation: Comment:

(i) Rd ← (Z) Z: Unchanged

(ii) Rd ← (Z) Z ← Z + 1 Z: Post increment

(iii) Z ← Z -1 Rd ← (Z) Z: Pre decrement

(iiii) Rd ← (Z+q) Z: Unchanged, q: Displacement

Syntax: Operands: Program Counter:

(i) LD Rd, Z 0 ≤ d ≤ 31 PC ← PC + 1

(ii) LD Rd, Z+ 0 ≤ d ≤ 31 PC ← PC + 1

(iii) LD Rd, -Z 0 ≤ d ≤ 31 PC ← PC + 1

(iiii) LDD Rd, Z+q 0 ≤ d ≤ 31, 0 ≤ q ≤ 63 PC ← PC + 1

88 AVR Instruction Set

0856E–AVR–11/05

16-bit Opcode:

Status Register (SREG) and Boolean Formula:

Example:

clr r31 ; Clear Z high byte

ldi r30,$60 ; Set Z low byte to $60

ld r0,Z+ ; Load r0 with data space loc. $60(Z post inc)

ld r1,Z ; Load r1 with data space loc. $61

ldi r30,$63 ; Set Z low byte to $63

ld r2,Z ; Load r2 with data space loc. $63

ld r3,-Z ; Load r3 with data space loc. $62(Z pre dec)

ldd r4,Z+2 ; Load r4 with data space loc. $64

Words: 1 (2 bytes)

Cycles: 2

(i) 1000 000d dddd 0000

(ii) 1001 000d dddd 0001

(iii) 1001 000d dddd 0010

(iiii) 10q0 qq0d dddd 0qqq

ITHSVNZC

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AVR Instruction Set

0856E–AVR–11/05

LDI – Load Immediate

Description:

Loads an 8 bit constant directly to register 16 to 31.

Operation:

(i) Rd ← K

Syntax: Operands: Program Counter:

(i) LDI Rd,K 16 ≤ d ≤ 31, 0 ≤ K ≤ 255 PC ← PC + 1

16-bit Opcode:

Status Register (SREG) and Boolean Formula:

Example:

clr r31 ; Clear Z high byte

ldi r30,$F0 ; Set Z low byte to $F0

lpm ; Load constant from Program

; memory pointed to by Z

Words: 1 (2 bytes)

Cycles: 1

1110 KKKK dddd KKKK

ITHSVNZC

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90 AVR Instruction Set

0856E–AVR–11/05

LDS – Load Direct from Data Space

Description:

Loads one byte from the data space to a register. For parts with SRAM, the data space consists of the Register File, I/O

memory and internal SRAM (and external SRAM if applicable). For parts without SRAM, the data space consists of the reg-

ister file only. The EEPROM has a separate address space.

A 16-bit address must be supplied. Memory access is limited to the current data segment of 64K bytes. The LDS instruction

uses the RAMPD Register to access memory above 64K bytes. To access another data segment in devices with more than

64K bytes data space, the RAMPD in register in the I/O area has to be changed.

This instruction is not available in all devices. Refer to the device specific instruction set summary.

Operation:

(i) Rd ← (k)

Syntax: Operands: Program Counter:

(i) LDS Rd,k 0 ≤ d ≤ 31, 0 ≤ k ≤ 65535 PC ← PC + 2

32-bit Opcode:

Status Register (SREG) and Boolean Formula:

Example:

lds r2,$FF00 ; Load r2 with the contents of data space location $FF00

add r2,r1 ; add r1 to r2

sts $FF00,r2 ; Write back

Words: 2 (4 bytes)

Cycles: 2

1001 000d dddd 0000

kkkk kkkk kkkk kkkk

ITHSVNZC

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AVR Instruction Set

0856E–AVR–11/05

LPM – Load Program Memory

Description:

Loads one byte pointed to by the Z-register into the destination register Rd. This instruction features a 100% space effec-

tive constant initialization or constant data fetch. The Program memory is organized in 16-bit words while the Z-pointer is a

byte address. Thus, the least significant bit of the Z-pointer selects either low byte (ZLSB = 0) or high byte (ZLSB = 1). This

instruction can address the first 64K bytes (32K words) of Program memory. The Z-pointer Register can either be left

unchanged by the operation, or it can be incremented. The incrementation does not apply to the RAMPZ Register.

Devices with Self-Programming capability can use the LPM instruction to read the Fuse and Lock bit values. Refer to the

device documentation for a detailed description.

Not all variants of the LPM instruction are available in all devices. Refer to the device specific instruction set summary. The

LPM instruction is not implemented at all in the AT90S1200 device.

The result of these combinations is undefined:

LPM r30, Z+

LPM r31, Z+

Operation: Comment:

(i) R0 ← (Z) Z: Unchanged, R0 implied destination register

(ii) Rd ← (Z) Z: Unchanged

(iii) Rd ← (Z) Z ← Z + 1 Z: Post incremented

Syntax: Operands: Program Counter:

(i) LPM None, R0 implied PC ← PC + 1

(ii) LPM Rd, Z 0 ≤ d ≤ 31 PC ← PC + 1

(iii) LPM Rd, Z+ 0 ≤ d ≤ 31 PC ← PC + 1

16-bit Opcode:

Status Register (SREG) and Boolean Formula:

Example:

ldi ZH, high(Table_1<<1); Initialize Z-pointer

ldi ZL, low(Table_1<<1)

lpm r16, Z ; Load constant from Program

; Memory pointed to by Z (r31:r30)

...

Table_1:

.dw 0x5876 ; 0x76 is addresses when ZLSB = 0

; 0x58 is addresses when ZLSB = 1

...

(i) 1001 0101 1100 1000

(ii) 1001 000d dddd 0100

(iii) 1001 000d dddd 0101

ITHSVNZC

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92 AVR Instruction Set

0856E–AVR–11/05

Words: 1 (2 bytes)

Cycles: 3

AVR Instruction Set

0856E–AVR–11/05

LSL – Logical Shift Left

Description:

Shifts all bits in Rd one place to the left. Bit 0 is cleared. Bit 7 is loaded into the C Flag of the SREG. This operation effec-

tively multiplies signed and unsigned values by two.

Operation:

(i)

Syntax: Operands: Program Counter:

(i) LSL Rd 0 ≤ d ≤ 31 PC ← PC + 1

16-bit Opcode: (see ADD Rd,Rd)

Status Register (SREG) and Boolean Formula:

H: Rd3

S: N ⊕ V, For signed tests.

V: N ⊕ C (For N and C after the shift)

N: R7

Set if MSB of the result is set; cleared otherwise.

Z: R7• R6 •R5• R4• R3 •R2• R1• R0

Set if the result is $00; cleared otherwise.

C: Rd7

Set if, before the shift, the MSB of Rd was set; cleared otherwise.

R (Result) equals Rd after the operation.

Example:

add r0,r4 ; Add r4 to r0

lsl r0 ; Multiply r0 by 2

Words: 1 (2 bytes)

Cycles: 1

←

C←b7 - - - - - - - - - - - - - - - - - - b0 ←0

0000 11dd dddd dddd

ITHSVNZC

––⇔⇔⇔⇔⇔⇔

94 AVR Instruction Set

0856E–AVR–11/05

LSR – Logical Shift Right

Description:

Shifts all bits in Rd one place to the right. Bit 7 is cleared. Bit 0 is loaded into the C Flag of the SREG. This operation effec-

tively divides an unsigned value by two. The C Flag can be used to round the result.

Operation:

Syntax: Operands: Program Counter:

(i) LSR Rd 0 ≤ d ≤ 31 PC ← PC + 1

16-bit Opcode:

Status Register (SREG) and Boolean Formula:

S: N ⊕ V, For signed tests.

V: N ⊕ C (For N and C after the shift)

N: 0

Z: R7• R6 •R5• R4• R3 •R2• R1• R0

Set if the result is $00; cleared otherwise.

C: Rd0

Set if, before the shift, the LSB of Rd was set; cleared otherwise.

R (Result) equals Rd after the operation.

Example:

add r0,r4 ; Add r4 to r0

lsr r0 ; Divide r0 by 2

Words: 1 (2 bytes)

Cycles: 1

→

0→b7 - - - - - - - - - - - - - - - - - - b0 →C

1001 010d dddd 0110

ITHSVNZC

–– –⇔⇔ 0⇔⇔

AVR Instruction Set

0856E–AVR–11/05

MOV – Copy Register

Description:

This instruction makes a copy of one register into another. The source register Rr is left unchanged, while the destination

Operation:

(i) Rd ← Rr

Syntax: Operands: Program Counter:

(i) MOV Rd,Rr 0 ≤ d ≤ 31, 0 ≤ r ≤ 31 PC ← PC + 1

16-bit Opcode:

Status Register (SREG) and Boolean Formula:

Example:

mov r16,r0 ; Copy r0 to r16

call check ; Call subroutine

...

check: cpi r16,$11 ; Compare r16 to $11

...

ret ; Return from subroutine

Words: 1 (2 bytes)

Cycles: 1

0010 11rd dddd rrrr

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96 AVR Instruction Set

0856E–AVR–11/05

MOVW – Copy Register Word

Description:

This instruction makes a copy of one register pair into another register pair. The source register pair Rr+1:Rr is left

unchanged, while the destination register pair Rd+1:Rd is loaded with a copy of Rr + 1:Rr.

This instruction is not available in all devices. Refer to the device specific instruction set summary.

Operation:

(i) Rd+1:Rd ← Rr+1:Rr

Syntax: Operands: Program Counter:

(i) MOVW Rd+1:Rd,Rr+1Rrd ∈ {0,2,...,30}, r ∈ {0,2,...,30} PC ← PC + 1

16-bit Opcode:

Status Register (SREG) and Boolean Formula:

Example:

movw r17:16,r1:r0 ; Copy r1:r0 to r17:r16

call check ; Call subroutine

...

check: cpi r16,$11 ; Compare r16 to $11

...

cpi r17,$32 ; Compare r17 to $32

...

ret ; Return from subroutine

Words: 1 (2 bytes)

Cycles: 1

0000 0001 dddd rrrr

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AVR Instruction Set

0856E–AVR–11/05

MUL – Multiply Unsigned

Description:

This instruction performs 8-bit × 8-bit → 16-bit unsigned multiplication.

The multiplicand Rd and the multiplier Rr are two registers containing unsigned numbers. The 16-bit unsigned product is

placed in R1 (high byte) and R0 (low byte). Note that if the multiplicand or the multiplier is selected from R0 or R1 the result

will overwrite those after multiplication.

This instruction is not available in all devices. Refer to the device specific instruction set summary.

Operation:

(i) R1:R0 ← Rd × Rr (unsigned ← unsigned × unsigned)

Syntax: Operands: Program Counter:

(i) MUL Rd,Rr 0 ≤ d ≤ 31, 0 ≤ r ≤ 31 PC ← PC + 1

16-bit Opcode:

Status Register (SREG) and Boolean Formula:

C: R15

Set if bit 15 of the result is set; cleared otherwise.

Z: R15 •R14 •R13 •R12 •R11 •R10 •R9 •R8 •R7• R6• R5• R4• R3• R2 •R1• R0

Set if the result is $0000; cleared otherwise.

R (Result) equals R1,R0 after the operation.

Example:

mul r5,r4 ; Multiply unsigned r5 and r4

movw r4,r0 ; Copy result back in r5:r4

Words: 1 (2 bytes)

Cycles: 2

Rd Rr R1 R0

Multiplicand ×Multiplier →Product High Product Low

88 16

1001 11rd dddd rrrr

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⇔⇔

98 AVR Instruction Set

0856E–AVR–11/05

MULS – Multiply Signed

Description:

This instruction performs 8-bit × 8-bit → 16-bit signed multiplication.

The multiplicand Rd and the multiplier Rr are two registers containing signed numbers. The 16-bit signed product is placed

in R1 (high byte) and R0 (low byte).

This instruction is not available in all devices. Refer to the device specific instruction set summary.

Operation:

(i) R1:R0 ← Rd × Rr (signed ← signed × signed)

Syntax: Operands: Program Counter:

(i) MULS Rd,Rr 16 ≤ d ≤ 31, 16 ≤ r ≤ 31 PC ← PC + 1

16-bit Opcode:

Status Register (SREG) and Boolean Formula:

C: R15

Set if bit 15 of the result is set; cleared otherwise.

Z: R15 •R14 •R13 •R12 •R11 •R10 •R9 •R8 •R7• R6• R5• R4• R3• R2 •R1• R0

Set if the result is $0000; cleared otherwise.

R (Result) equals R1,R0 after the operation.

Example:

muls r21,r20 ; Multiply signed r21 and r20

movw r20,r0 ; Copy result back in r21:r20

Words: 1 (2 bytes)

Cycles: 2

Rd Rr R1 R0

Multiplicand ×Multiplier →Product High Product Low

88 16

0000 0010 dddd rrrr

ITHSVNZC

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⇔⇔

AVR Instruction Set

0856E–AVR–11/05

MULSU – Multiply Signed with Unsigned

Description:

This instruction performs 8-bit × 8-bit → 16-bit multiplication of a signed and an unsigned number.

The multiplicand Rd and the multiplier Rr are two registers. The multiplicand Rd is a signed number, and the multiplier Rr is

unsigned. The 16-bit signed product is placed in R1 (high byte) and R0 (low byte).

This instruction is not available in all devices. Refer to the device specific instruction set summary.

Operation:

(i) R1:R0 ← Rd × Rr (signed ← signed × unsigned)

Syntax: Operands: Program Counter:

(i) MULSU Rd,Rr 16 ≤ d ≤ 23, 16 ≤ r ≤ 23 PC ← PC + 1

16-bit Opcode:

Status Register (SREG) and Boolean Formula:

C: R15

Set if bit 15 of the result is set; cleared otherwise.

Z: R15 •R14 •R13 •R12 •R11 •R10 •R9 •R8 •R7• R6• R5• R4• R3• R2 •R1• R0

Set if the result is $0000; cleared otherwise.

R (Result) equals R1,R0 after the operation.

Example:

;******************************************************************************

;* DESCRIPTION

;*Signed multiply of two 16-bit numbers with 32-bit result.

;* USAGE

;*r19:r18:r17:r16 = r23:r22 * r21:r20

;******************************************************************************

muls16x16_32:

clrr2

mulsr23, r21; (signed)ah * (signed)bh

Rd Rr R1 R0

Multiplicand ×Multiplier →Product High Product Low

88 16

0000 0011 0ddd 0rrr

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⇔⇔

100 AVR Instruction Set

0856E–AVR–11/05

movwr19:r18, r1:r0

mulr22, r20; al * bl

movwr17:r16, r1:r0

mulsur23, r20; (signed)ah * bl

sbcr19, r2

addr17, r0

adcr18, r1

adcr19, r2

mulsur21, r22; (signed)bh * al

sbcr19, r2

addr17, r0

adcr18, r1

adcr19, r2

ret

Words: 1 (2 bytes)

Cycles: 2

101

AVR Instruction Set

0856E–AVR–11/05

NEG – Two’s Complement

Description:

Replaces the contents of register Rd with its two’s complement; the value $80 is left unchanged.

Operation:

(i) Rd ← $00 - Rd

Syntax: Operands: Program Counter:

(i) NEG Rd 0 ≤ d ≤ 31 PC ← PC + 1

16-bit Opcode:

Status Register (SREG) and Boolean Formula:

H: R3 + Rd3

Set if there was a borrow from bit 3; cleared otherwise

S: N ⊕ V

For signed tests.

V: R7• R6 •R5• R4• R3 •R2• R1• R0

Set if there is a two’s complement overflow from the implied subtraction from zero; cleared otherwise. A two’s com-

plement overflow will occur if and only if the contents of the Register after operation (Result) is $80.

N: R7

Set if MSB of the result is set; cleared otherwise.

Z: R7• R6 •R5• R4• R3 •R2• R1• R0

Set if the result is $00; Cleared otherwise.

C: R7 + R6 + R5 + R4 + R3 + R2 + R1 + R0

Set if there is a borrow in the implied subtraction from zero; cleared otherwise. The C Flag will be set in all cases

except when the contents of Register after operation is $00.

R (Result) equals Rd after the operation.

Example:

sub r11,r0 ; Subtract r0 from r11

brpl positive ; Branch if result positive

neg r11 ; Take two’s complement of r11

positive: nop ; Branch destination (do nothing)

Words: 1 (2 bytes)

Cycles: 1

1001 010d dddd 0001

ITHSVNZC

––⇔⇔⇔⇔⇔⇔

102 AVR Instruction Set

0856E–AVR–11/05

NOP – No Operation

Description:

This instruction performs a single cycle No Operation.

Operation:

(i) No

Syntax: Operands: Program Counter:

(i) NOP None PC ← PC + 1

16-bit Opcode:

Status Register (SREG) and Boolean Formula:

Example:

clr r16 ; Clear r16

ser r17 ; Set r17

out $18,r16 ; Write zeros to Port B

nop ; Wait (do nothing)

out $18,r17 ; Write ones to Port B

Words: 1 (2 bytes)

Cycles: 1

0000 0000 0000 0000

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103

AVR Instruction Set

0856E–AVR–11/05

OR – Logical OR

Description:

Performs the logical OR between the contents of register Rd and register Rr and places the result in the destination register

Rd.

Operation:

(i) Rd ← Rd v Rr

Syntax: Operands: Program Counter:

(i) OR Rd,Rr 0 ≤ d ≤ 31, 0 ≤ r ≤ 31 PC ← PC + 1

16-bit Opcode:

Status Register (SREG) and Boolean Formula:

S: N ⊕ V, For signed tests.

V: 0

Cleared

N: R7

Set if MSB of the result is set; cleared otherwise.

Z: R7• R6 •R5• R4• R3 •R2• R1• R0

Set if the result is $00; cleared otherwise.

R (Result) equals Rd after the operation.

Example:

or r15,r16 ; Do bitwise or between registers

bst r15,6 ; Store bit 6 of r15 in T Flag

brts ok ; Branch if T Flag set

...

ok: nop ; Branch destination (do nothing)

Words: 1 (2 bytes)

Cycles: 1

0010 10rd dddd rrrr

ITHSVNZC

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104 AVR Instruction Set

0856E–AVR–11/05

ORI – Logical OR with Immediate

Description:

Performs the logical OR between the contents of register Rd and a constant and places the result in the destination register

Rd.

Operation:

(i) Rd ← Rd v K

Syntax: Operands: Program Counter:

(i) ORI Rd,K 16 ≤ d ≤ 31, 0 ≤ K ≤ 255 PC ← PC + 1

16-bit Opcode:

Status Register (SREG) and Boolean Formula:

S: N ⊕ V, For signed tests.

V: 0

Cleared

N: R7

Set if MSB of the result is set; cleared otherwise.

Z: R7• R6 •R5• R4• R3 •R2• R1• R0

Set if the result is $00; cleared otherwise.

R (Result) equals Rd after the operation.

Example:

ori r16,$F0 ; Set high nibble of r16

ori r17,1 ; Set bit 0 of r17

Words: 1 (2 bytes)

Cycles: 1

0110 KKKK dddd KKKK

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–– –⇔0⇔⇔ –

105

AVR Instruction Set

0856E–AVR–11/05

OUT – Store Register to I/O Location

Description:

Stores data from register Rr in the Register File to I/O Space (Ports, Timers, Configuration Registers etc.).

Operation:

(i) I/O(A) ← Rr

Syntax: Operands: Program Counter:

(i) OUT A,Rr 0 ≤ r ≤ 31, 0 ≤ A ≤ 63 PC ← PC + 1

16-bit Opcode:

Status Register (SREG) and Boolean Formula:

Example:

clr r16 ; Clear r16

ser r17 ; Set r17

out $18,r16 ; Write zeros to Port B

nop ; Wait (do nothing)

out $18,r17 ; Write ones to Port B

Words: 1 (2 bytes)

Cycles: 1

1011 1AAr rrrr AAAA

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106 AVR Instruction Set

0856E–AVR–11/05

POP – Pop Register from Stack

Description:

This instruction loads register Rd with a byte from the STACK. The Stack Pointer is pre-incremented by 1 before the POP.

This instruction is not available in all devices. Refer to the device specific instruction set summary.

Operation:

(i) Rd ← STACK

Syntax: Operands: Program Counter: Stack:

(i) POP Rd 0 ≤ d ≤ 31 PC ← PC + 1 SP ← SP + 1

16-bit Opcode:

Status Register (SREG) and Boolean Formula:

Example:

call routine ; Call subroutine

...

routine: push r14 ; Save r14 on the Stack

push r13 ; Save r13 on the Stack

...

pop r13 ; Restore r13

pop r14 ; Restore r14

ret ; Return from subroutine

Words: 1 (2 bytes)

Cycles: 2

1001 000d dddd 1111

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107

AVR Instruction Set

0856E–AVR–11/05

PUSH – Push Register on Stack

Description:

This instruction stores the contents of register Rr on the STACK. The Stack Pointer is post-decremented by 1 after the

PUSH.

This instruction is not available in all devices. Refer to the device specific instruction set summary.

Operation:

(i) STACK ← Rr

Syntax: Operands: Program Counter: Stack:

(i) PUSH Rr 0 ≤ r ≤ 31 PC ← PC + 1 SP ← SP - 1

16-bit Opcode:

Status Register (SREG) and Boolean Formula:

Example:

call routine ; Call subroutine

...

routine: push r14 ; Save r14 on the Stack

push r13 ; Save r13 on the Stack

...

pop r13 ; Restore r13

pop r14 ; Restore r14

ret ; Return from subroutine

Words: 1 (2 bytes)

Cycles: 2

1001 001d dddd 1111

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108 AVR Instruction Set

0856E–AVR–11/05

RCALL – Relative Call to Subroutine

Description:

Relative call to an address within PC - 2K + 1 and PC + 2K (words). The return address (the instruction after the RCALL) is

stored onto the Stack. See also CALL. For AVR microcontrollers with Program memory not exceeding 4K words (8K bytes)

this instruction can address the entire memory from every address location. The Stack Pointer uses a post-decrement

scheme during RCALL.

Operation:

(i) PC ← PC + k + 1 Devices with 16 bits PC, 128K bytes Program memory maximum.

(ii) PC ← PC + k + 1 Devices with 22 bits PC, 8M bytes Program memory maximum.

Syntax: Operands: Program Counter: Stack:

(i) RCALL k -2K ≤ k < 2K PC ← PC + k + 1 STACK ← PC + 1

SP ← SP - 2 (2 bytes, 16 bits)

(ii) RCALL k -2K ≤ k < 2K PC ← PC + k + 1 STACK ← PC + 1

SP ← SP - 3 (3 bytes, 22 bits)

16-bit Opcode:

Status Register (SREG) and Boolean Formula:

Example:

rcall routine ; Call subroutine

...

routine: push r14 ; Save r14 on the Stack

...

pop r14 ; Restore r14

ret ; Return from subroutine

Words: 1 (2 bytes)

Cycles: 3 devices with 16-bit PC

4 devices with 22-bit PC

1101 kkkk kkkk kkkk

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109

AVR Instruction Set

0856E–AVR–11/05

RET – Return from Subroutine

Description:

Returns from subroutine. The return address is loaded from the STACK. The Stack Pointer uses a pre-increment scheme

during RET.

Operation:

(i) PC(15:0) ← STACK Devices with 16 bits PC, 128K bytes Program memory maximum.

(ii) PC(21:0) ← STACKDevices with 22 bits PC, 8M bytes Program memory maximum.

Syntax: Operands: Program Counter: Stack:

(i) RET None See Operation SP←SP + 2, (2bytes,16 bits)

(ii) RET None See Operation SP←SP + 3, (3bytes,22 bits)

16-bit Opcode:

Status Register (SREG) and Boolean Formula:

Example:

call routine ; Call subroutine

...

routine: push r14 ; Save r14 on the Stack

...

pop r14 ; Restore r14

ret ; Return from subroutine

Words: 1 (2 bytes)

Cycles: 4 devices with 16-bit PC

5 devices with 22-bit PC

1001 0101 0000 1000

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110 AVR Instruction Set

0856E–AVR–11/05

RETI – Return from Interrupt

Description:

Returns from interrupt. The return address is loaded from the STACK and the Global Interrupt Flag is set.

Note that the Status Register is not automatically stored when entering an interrupt routine, and it is not restored when

returning from an interrupt routine. This must be handled by the application program. The Stack Pointer uses a pre-incre-

ment scheme during RETI.

Operation:

(i) PC(15:0) ← STACK Devices with 16 bits PC, 128K bytes Program memory maximum.

(ii) PC(21:0) ← STACKDevices with 22 bits PC, 8M bytes Program memory maximum.

Syntax: Operands: Program Counter: Stack

(i) RETI None See Operation SP ← SP + 2 (2 bytes, 16 bits)

(ii) RETI None See Operation SP ← SP + 3 (3 bytes, 22 bits)

16-bit Opcode:

Status Register (SREG) and Boolean Formula:

I: 1

The I Flag is set.

Example:

...

extint: push r0 ; Save r0 on the Stack

...

pop r0 ; Restore r0

reti ; Return and enable interrupts

Words: 1 (2 bytes)

Cycles: 4 devices with 16-bit PC

5 devices with 22-bit PC

1001 0101 0001 1000

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1–––––––

111

AVR Instruction Set

0856E–AVR–11/05

RJMP – Relative Jump

Description:

Relative jump to an address within PC - 2K +1 and PC + 2K (words). For AVR microcontrollers with Program memory not

exceeding 4K words (8K bytes) this instruction can address the entire memory from every address location. See also JMP.

Operation:

(i) PC ← PC + k + 1

Syntax: Operands: Program Counter: Stack

(i) RJMP k -2K ≤ k < 2K PC ← PC + k + 1 Unchanged

16-bit Opcode:

Status Register (SREG) and Boolean Formula:

Example:

cpi r16,$42 ; Compare r16 to $42

brne error ; Branch if r16 <> $42

rjmp ok ; Unconditional branch

error: add r16,r17 ; Add r17 to r16

inc r16 ; Increment r16

ok: nop ; Destination for rjmp (do nothing)

Words: 1 (2 bytes)

Cycles: 2

1100 kkkk kkkk kkkk

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112 AVR Instruction Set

0856E–AVR–11/05

ROL – Rotate Left trough Carry

Description:

Shifts all bits in Rd one place to the left. The C Flag is shifted into bit 0 of Rd. Bit 7 is shifted into the C Flag. This operation,

combined with LSL, effectively multiplies multi-byte signed and unsigned values by two.

Operation:

Syntax: Operands: Program Counter:

(i) ROL Rd 0 ≤ d ≤ 31 PC ← PC + 1

16-bit Opcode: (see ADC Rd,Rd)

Status Register (SREG) and Boolean Formula:

H: Rd3

S: N ⊕ V, For signed tests.

V: N ⊕ C (For N and C after the shift)

N: R7

Set if MSB of the result is set; cleared otherwise.

Z: R7• R6 •R5• R4• R3 •R2• R1• R0

Set if the result is $00; cleared otherwise.

C: Rd7

Set if, before the shift, the MSB of Rd was set; cleared otherwise.

R (Result) equals Rd after the operation.

Example:

lsl r18 ; Multiply r19:r18 by two

rol r19 ; r19:r18 is a signed or unsigned two-byte integer

brcs oneenc ; Branch if carry set

...

oneenc: nop ; Branch destination (do nothing)

Words: 1 (2 bytes)

Cycles: 1

←

C ¨ b7 - - - - - - - - - - - - - - - - - - b0 ←C

0001 11dd dddd dddd

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113

AVR Instruction Set

0856E–AVR–11/05

ROR – Rotate Right through Carry

Description:

Shifts all bits in Rd one place to the right. The C Flag is shifted into bit 7 of Rd. Bit 0 is shifted into the C Flag. This opera-

tion, combined with ASR, effectively divides multi-byte signed values by two. Combined with LSR it effectively divides multi-

byte unsigned values by two. The Carry Flag can be used to round the result.

Operation:

Syntax: Operands: Program Counter:

(i) ROR Rd 0 ≤ d ≤ 31 PC ← PC + 1

16-bit Opcode:

Status Register (SREG) and Boolean Formula:

S: N ⊕ V, For signed tests.

V: N ⊕ C (For N and C after the shift)

N: R7

Set if MSB of the result is set; cleared otherwise.

Z: R7• R6 •R5• R4• R3 •R2• R1• R0

Set if the result is $00; cleared otherwise.

C: Rd0

Set if, before the shift, the LSB of Rd was set; cleared otherwise.

R (Result) equals Rd after the operation.

Example:

lsr r19 ; Divide r19:r18 by two

ror r18 ; r19:r18 is an unsigned two-byte integer

brcc zeroenc1 ; Branch if carry cleared

asr r17 ; Divide r17:r16 by two

ror r16 ; r17:r16 is a signed two-byte integer

brcc zeroenc2 ; Branch if carry cleared

...

zeroenc1: nop ; Branch destination (do nothing)

...

→

C→b7 - - - - - - - - - - - - - - - - - - b0 →C

1001 010d dddd 0111

ITHSVNZC

–– –⇔⇔⇔⇔⇔

114 AVR Instruction Set

0856E–AVR–11/05

zeroenc1: nop ; Branch destination (do nothing)

Words: 1 (2 bytes)

Cycles: 1

115

AVR Instruction Set

0856E–AVR–11/05

SBC – Subtract with Carry

Description:

Subtracts two registers and subtracts with the C Flag and places the result in the destination register Rd.

Operation:

(i) Rd ← Rd - Rr - C

Syntax: Operands: Program Counter:

(i) SBC Rd,Rr 0 ≤ d ≤ 31, 0 ≤ r ≤ 31 PC ← PC + 1

16-bit Opcode:

Status Register and Boolean Formula:

H: Rd3• Rr3 + Rr3• R3 + R3 •Rd3

Set if there was a borrow from bit 3; cleared otherwise

S: N ⊕ V, For signed tests.

V: Rd7 •Rr7• R7 +Rd7 •Rr7 •R7

Set if two’s complement overflow resulted from the operation; cleared otherwise.

N: R7

Set if MSB of the result is set; cleared otherwise.

Z: R7• R6 •R5• R4• R3 •R2• R1• R0• Z

Previous value remains unchanged when the result is zero; cleared otherwise.

C: Rd7 •Rr7+ Rr7 •R7 +R7 •Rd7

Set if the absolute value of the contents of Rr plus previous carry is larger than the absolute value of the Rd; cleared

otherwise.

R (Result) equals Rd after the operation.

Example:

; Subtract r1:r0 from r3:r2

sub r2,r0 ; Subtract low byte

sbc r3,r1 ; Subtract with carry high byte

Words: 1 (2 bytes)

Cycles: 1

0000 10rd dddd rrrr

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116 AVR Instruction Set

0856E–AVR–11/05

SBCI – Subtract Immediate with Carry

Description:

Subtracts a constant from a register and subtracts with the C Flag and places the result in the destination register Rd.

Operation:

(i) Rd ← Rd - K - C

Syntax: Operands: Program Counter:

(i) SBCI Rd,K 16 ≤ d ≤ 31, 0 ≤ K ≤ 255 PC ← PC + 1

16-bit Opcode:

Status Register and Boolean Formula:

H: Rd3• K3 + K3• R3 + R3 •Rd3

Set if there was a borrow from bit 3; cleared otherwise

S: N ⊕ V, For signed tests.

V: Rd7 •K7• R7 +Rd7 •K7 •R7

Set if two’s complement overflow resulted from the operation; cleared otherwise.

N: R7

Set if MSB of the result is set; cleared otherwise.

Z: R7• R6 •R5• R4• R3 •R2• R1• R0• Z

Previous value remains unchanged when the result is zero; cleared otherwise.

C: Rd7 •K7+ K7 • R7 +R7 •Rd7

Set if the absolute value of the constant plus previous carry is larger than the absolute value of Rd; cleared other-

wise.

R (Result) equals Rd after the operation.

Example:

; Subtract $4F23 from r17:r16

subi r16,$23 ; Subtract low byte

sbci r17,$4F ; Subtract with carry high byte

Words: 1 (2 bytes)

Cycles: 1

0100 KKKK dddd KKKK

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117

AVR Instruction Set

0856E–AVR–11/05

SBI – Set Bit in I/O Register

Description:

Sets a specified bit in an I/O Register. This instruction operates on the lower 32 I/O Registers – addresses 0-31.

Operation:

(i) I/O(A,b) ← 1

Syntax: Operands: Program Counter:

(i) SBI A,b 0 ≤ A ≤ 31, 0 ≤ b ≤ 7PC ← PC + 1

16-bit Opcode:

Status Register (SREG) and Boolean Formula:

Example:

out $1E,r0 ; Write EEPROM address

sbi $1C,0 ; Set read bit in EECR

in r1,$1D ; Read EEPROM data

Words: 1 (2 bytes)

Cycles: 2

1001 1010 AAAA Abbb

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118 AVR Instruction Set

0856E–AVR–11/05

SBIC – Skip if Bit in I/O Register is Cleared

Description:

This instruction tests a single bit in an I/O Register and skips the next instruction if the bit is cleared. This instruction oper-

ates on the lower 32 I/O Registers – addresses 0-31.

Operation:

(i) If I/O(A,b) = 0 then PC ← PC + 2 (or 3) else PC ← PC + 1

Syntax: Operands: Program Counter:

(i) SBIC A,b 0 ≤ A ≤ 31, 0 ≤ b ≤ 7PC ← PC + 1, Condition false - no skip

PC ← PC + 2, Skip a one word instruction

PC ← PC + 3, Skip a two word instruction

16-bit Opcode:

Status Register (SREG) and Boolean Formula:

Example:

e2wait: sbic $1C,1 ; Skip next inst. if EEWE cleared

rjmp e2wait ; EEPROM write not finished

nop ; Continue (do nothing)

Words: 1 (2 bytes)

Cycles: 1 if condition is false (no skip)

2 if condition is true (skip is executed) and the instruction skipped is 1 word

3 if condition is true (skip is executed) and the instruction skipped is 2 words

1001 1001 AAAA Abbb

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119

AVR Instruction Set

0856E–AVR–11/05

SBIS – Skip if Bit in I/O Register is Set

Description:

This instruction tests a single bit in an I/O Register and skips the next instruction if the bit is set. This instruction operates on

the lower 32 I/O Registers – addresses 0-31.

Operation:

(i) If I/O(A,b) = 1 then PC ← PC + 2 (or 3) else PC ← PC + 1

Syntax: Operands: Program Counter:

(i) SBIS A,b 0 ≤ A ≤ 31, 0 ≤ b ≤ 7PC ← PC + 1, Condition false - no skip

PC ← PC + 2, Skip a one word instruction

PC ← PC + 3, Skip a two word instruction

16-bit Opcode:

Status Register (SREG) and Boolean Formula:

Example:

waitset: sbis $10,0 ; Skip next inst. if bit 0 in Port D set

rjmp waitset ; Bit not set

nop ; Continue (do nothing)

Words: 1 (2 bytes)

Cycles: 1 if condition is false (no skip)

2 if condition is true (skip is executed) and the instruction skipped is 1 word

3 if condition is true (skip is executed) and the instruction skipped is 2 words

1001 1011 AAAA Abbb

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120 AVR Instruction Set

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SBIW – Subtract Immediate from Word

Description:

Subtracts an immediate value (0-63) from a register pair and places the result in the register pair. This instruction operates

on the upper four register pairs, and is well suited for operations on the Pointer Registers.

This instruction is not available in all devices. Refer to the device specific instruction set summary.

Operation:

(i) Rd+1:Rd ← Rd+1:Rd - K

Syntax: Operands: Program Counter:

(i) SBIW Rd+1:Rd,K d ∈ {24,26,28,30}, 0 ≤ K ≤ 63 PC ← PC + 1

16-bit Opcode:

Status Register (SREG) and Boolean Formula:

S: N ⊕ V, For signed tests.

V: Rdh7 •R15

Set if two’s complement overflow resulted from the operation; cleared otherwise.

N: R15

Set if MSB of the result is set; cleared otherwise.

Z: R15• R14 •R13 •R12 •R11• R10• R9• R8• R7• R6 •R5• R4• R3 •R2• R1• R0

Set if the result is $0000; cleared otherwise.

C: R15• Rdh7

Set if the absolute value of K is larger than the absolute value of Rd; cleared otherwise.

R (Result) equals Rdh:Rdl after the operation (Rdh7-Rdh0 = R15-R8, Rdl7-Rdl0=R7-R0).

Example:

sbiw r25:r24,1 ; Subtract 1 from r25:r24

sbiw YH:YL,63 ; Subtract 63 from the Y-pointer(r29:r28)

Words: 1 (2 bytes)

Cycles: 2

1001 0111 KKdd KKKK

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AVR Instruction Set

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SBR – Set Bits in Register

Description:

Sets specified bits in register Rd. Performs the logical ORI between the contents of register Rd and a constant mask K and

places the result in the destination register Rd.

Operation:

(i) Rd ← Rd v K

Syntax: Operands: Program Counter:

(i) SBR Rd,K 16 ≤ d ≤ 31, 0 ≤ K ≤ 255 PC ← PC + 1

16-bit Opcode:

Status Register (SREG) and Boolean Formula:

S: N ⊕ V, For signed tests.

V: 0

Cleared

N: R7

Set if MSB of the result is set; cleared otherwise.

Z: R7• R6 •R5• R4• R3 •R2• R1• R0

Set if the result is $00; cleared otherwise.

R (Result) equals Rd after the operation.

Example:

sbr r16,3 ; Set bits 0 and 1 in r16

sbr r17,$F0 ; Set 4 MSB in r17

Words: 1 (2 bytes)

Cycles: 1

0110 KKKK dddd KKKK

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122 AVR Instruction Set

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SBRC – Skip if Bit in Register is Cleared

Description:

This instruction tests a single bit in a register and skips the next instruction if the bit is cleared.

Operation:

(i) If Rr(b) = 0 then PC ← PC + 2 (or 3) else PC ← PC + 1

Syntax: Operands: Program Counter:

(i) SBRC Rr,b 0 ≤ r ≤ 31, 0 ≤ b ≤ 7PC ← PC + 1, Condition false - no skip

PC ← PC + 2, Skip a one word instruction

PC ← PC + 3, Skip a two word instruction

16-bit Opcode:

Status Register (SREG) and Boolean Formula:

Example:

sub r0,r1 ; Subtract r1 from r0

sbrc r0,7 ; Skip if bit 7 in r0 cleared

sub r0,r1 ; Only executed if bit 7 in r0 not cleared

nop ; Continue (do nothing)

Words: 1 (2 bytes)

Cycles: 1 if condition is false (no skip)

2 if condition is true (skip is executed) and the instruction skipped is 1 word

3 if condition is true (skip is executed) and the instruction skipped is 2 words

1111 110r rrrr 0bbb

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SBRS – Skip if Bit in Register is Set

Description:

This instruction tests a single bit in a register and skips the next instruction if the bit is set.

Operation:

(i) If Rr(b) = 1 then PC ← PC + 2 (or 3) else PC ← PC + 1

Syntax: Operands: Program Counter:

(i) SBRS Rr,b 0 ≤ r ≤ 31, 0 ≤ b ≤ 7PC ← PC + 1, Condition false - no skip

PC ← PC + 2, Skip a one word instruction

PC ← PC + 3, Skip a two word instruction

16-bit Opcode:

Status Register (SREG) and Boolean Formula:

Example:

sub r0,r1 ; Subtract r1 from r0

sbrs r0,7 ; Skip if bit 7 in r0 set

neg r0 ; Only executed if bit 7 in r0 not set

nop ; Continue (do nothing)

Words: 1 (2 bytes)

Cycles: 1 if condition is false (no skip)

2 if condition is true (skip is executed) and the instruction skipped is 1 word

3 if condition is true (skip is executed) and the instruction skipped is 2 words

1111 111r rrrr 0bbb

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124 AVR Instruction Set

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SEC – Set Carry Flag

Description:

Sets the Carry Flag (C) in SREG (Status Register).

Operation:

(i) C ← 1

Syntax: Operands: Program Counter:

(i) SEC None PC ← PC + 1

16-bit Opcode:

Status Register (SREG) and Boolean Formula:

C: 1

Carry Flag set

Example:

sec ; Set Carry Flag

adc r0,r1 ; r0=r0+r1+1

Words: 1 (2 bytes)

Cycles: 1

1001 0100 0000 1000

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125

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SEH – Set Half Carry Flag

Description:

Sets the Half Carry (H) in SREG (Status Register).

Operation:

(i) H ← 1

Syntax: Operands: Program Counter:

(i) SEH None PC ← PC + 1

16-bit Opcode:

Status Register (SREG) and Boolean Formula:

H: 1

Half Carry Flag set

Example:

seh ; Set Half Carry Flag

Words: 1 (2 bytes)

Cycles: 1

1001 0100 0101 1000

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126 AVR Instruction Set

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SEI – Set Global Interrupt Flag

Description:

Sets the Global Interrupt Flag (I) in SREG (Status Register). The instruction following SEI will be executed before any pend-

ing interrupts.

Operation:

(i) I ← 1

Syntax: Operands: Program Counter:

(i) SEI None PC ← PC + 1

16-bit Opcode:

Status Register (SREG) and Boolean Formula:

I: 1

Global Interrupt Flag set

Example:

sei ; set global interrupt enable

sleep ; enter sleep, waiting for interrupt

; note: will enter sleep before any pending interrupt(s)

Words: 1 (2 bytes)

Cycles: 1

1001 0100 0111 1000

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SEN – Set Negative Flag

Description:

Sets the Negative Flag (N) in SREG (Status Register).

Operation:

(i) N ← 1

Syntax: Operands: Program Counter:

(i) SEN None PC ← PC + 1

16-bit Opcode:

Status Register (SREG) and Boolean Formula:

N: 1

Negative Flag set

Example:

add r2,r19 ; Add r19 to r2

sen ; Set Negative Flag

Words: 1 (2 bytes)

Cycles: 1

1001 0100 0010 1000

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128 AVR Instruction Set

0856E–AVR–11/05

SER – Set all Bits in Register

Description:

Loads $FF directly to register Rd.

Operation:

(i) Rd ← $FF

Syntax: Operands: Program Counter:

(i) SER Rd 16 ≤ d ≤ 31 PC ← PC + 1

16-bit Opcode:

Status Register (SREG) and Boolean Formula:

Example:

clr r16 ; Clear r16

ser r17 ; Set r17

out $18,r16 ; Write zeros to Port B

nop ; Delay (do nothing)

out $18,r17 ; Write ones to Port B

Words: 1 (2 bytes)

Cycles: 1

1110 1111 dddd 1111

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SES – Set Signed Flag

Description:

Sets the Signed Flag (S) in SREG (Status Register).

Operation:

(i) S ← 1

Syntax: Operands: Program Counter:

(i) SES None PC ← PC + 1

16-bit Opcode:

Status Register (SREG) and Boolean Formula:

S: 1

Signed Flag set

Example:

add r2,r19 ; Add r19 to r2

ses ; Set Negative Flag

Words: 1 (2 bytes)

Cycles: 1

1001 0100 0100 1000

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SET – Set T Flag

Description:

Sets the T Flag in SREG (Status Register).

Operation:

(i) T ← 1

Syntax: Operands: Program Counter:

(i) SET None PC ← PC + 1

16-bit Opcode:

Status Register (SREG) and Boolean Formula:

T: 1

T Flag set

Example:

set ; Set T Flag

Words: 1 (2 bytes)

Cycles: 1

1001 0100 0110 1000

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SEV – Set Overflow Flag

Description:

Sets the Overflow Flag (V) in SREG (Status Register).

Operation:

(i) V ← 1

Syntax: Operands: Program Counter:

(i) SEV None PC ← PC + 1

16-bit Opcode:

Status Register (SREG) and Boolean Formula:

V: 1

Overflow Flag set

Example:

add r2,r19 ; Add r19 to r2

sev ; Set Overflow Flag

Words: 1 (2 bytes)

Cycles: 1

1001 0100 0011 1000

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132 AVR Instruction Set

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SEZ – Set Zero Flag

Description:

Sets the Zero Flag (Z) in SREG (Status Register).

Operation:

(i) Z ← 1

Syntax: Operands: Program Counter:

(i) SEZ None PC ← PC + 1

16-bit Opcode:

Status Register (SREG) and Boolean Formula:

Z: 1

Zero Flag set

Example:

add r2,r19 ; Add r19 to r2

sez ; Set Zero Flag

Words: 1 (2 bytes)

Cycles: 1

1001 0100 0001 1000

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SLEEP

Description:

This instruction sets the circuit in sleep mode defined by the MCU Control Register.

Operation:

Refer to the device documentation for detailed description of SLEEP usage.

Syntax: Operands: Program Counter:

SLEEP None PC ← PC + 1

16-bit Opcode:

Status Register (SREG) and Boolean Formula:

Example:

mov r0,r11 ; Copy r11 to r0

ldi r16,(1<<SE) ; Enable sleep mode

out MCUCR, r16

sleep ; Put MCU in sleep mode

Words: 1 (2 bytes)

Cycles: 1

1001 0101 1000 1000

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134 AVR Instruction Set

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SPM – Store Program Memory

Description:

SPM can be used to erase a page in the Program memory, to write a page in the Program memory (that is already erased),

and to set Boot Loader Lock bits. In some devices, the Program memory can be written one word at a time, in other devices

an entire page can be programmed simultaneously after first filling a temporary page buffer. In all cases, the Program

memory must be erased one page at a time. When erasing the Program memory, the RAMPZ and Z-register are used as

page address. When writing the Program memory, the RAMPZ and Z-register are used as page or word address, and the

R1:R0 register pair is used as data(1). When setting the Boot Loader Lock bits, the R1:R0 register pair is used as data.

Refer to the device documentation for detailed description of SPM usage. This instruction can address the entire Program

memory.

This instruction is not available in all devices. Refer to the device specific instruction set summary.

Note: 1. R1 determines the instruction high byte, and R0 determines the instruction low byte.

Operation: Comment:

(i) (RAMPZ:Z) ← $ffff Erase Program memory page

(ii) (RAMPZ:Z) ← R1:R0 Write Program memory word

(iii) (RAMPZ:Z) ← R1:R0 Write temporary page buffer

(iv) (RAMPZ:Z) ← TEMP Write temporary page buffer to Program memory

(v) BLBITS ← R1:R0 Set Boot Loader Lock bits

Syntax: Operands: Program Counter:

(i)-(v) SPM None PC ← PC + 1

16-bit Opcode:

Status Register (SREG) and Boolean Formula:

Example:

;This example shows SPM write of one page for devices with page write

;- the routine writes one page of data from RAM to Flash

; the first data location in RAM is pointed to by the Y-pointer

; the first data location in Flash is pointed to by the Z-pointer

;- error handling is not included

;- the routine must be placed inside the boot space

; (at least the do_spm sub routine)

;- registers used: r0, r1, temp1, temp2, looplo, loophi, spmcrval

; (temp1, temp2, looplo, loophi, spmcrval must be defined by the user)

; storing and restoring of registers is not included in the routine

; register usage can be optimized at the expense of code size

.equPAGESIZEB = PAGESIZE*2;PAGESIZEB is page size in BYTES, not words

.org SMALLBOOTSTART

write_page:

1001 0101 1110 1000

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;page erase

ldispmcrval, (1<<PGERS) + (1<<SPMEN)

calldo_spm

;transfer data from RAM to Flash page buffer

ldilooplo, low(PAGESIZEB);init loop variable

ldiloophi, high(PAGESIZEB);not required for PAGESIZEB<=256

wrloop:ldr0, Y+

ldr1, Y+

ldispmcrval, (1<<SPMEN)

calldo_spm

adiwZH:ZL, 2

sbiwloophi:looplo, 2;use subi for PAGESIZEB<=256

brnewrloop

;execute page write

subiZL, low(PAGESIZEB);restore pointer

sbciZH, high(PAGESIZEB);not required for PAGESIZEB<=256

ldispmcrval, (1<<PGWRT) + (1<<SPMEN)

calldo_spm

;read back and check, optional

ldilooplo, low(PAGESIZEB);init loop variable

ldiloophi, high(PAGESIZEB);not required for PAGESIZEB<=256

subiYL, low(PAGESIZEB);restore pointer

sbciYH, high(PAGESIZEB)

rdloop:lpmr0, Z+

ldr1, Y+

cpser0, r1

jmperror

sbiwloophi:looplo, 2;use subi for PAGESIZEB<=256

brnerdloop

;return

ret

do_spm:

;input: spmcrval determines SPM action

;disable interrupts if enabled, store status

intemp2, SREG

cli

;check for previous SPM complete

wait:intemp1, SPMCR

sbrctemp1, SPMEN

rjmpwait

;SPM timed sequence

outSPMCR, spmcrval

spm

;restore SREG (to enable interrupts if originally enabled)

outSREG, temp2

136 AVR Instruction Set

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ret

Words: 1 (2 bytes)

Cycles: depends on the operation

137

AVR Instruction Set

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ST – Store Indirect From Register to Data Space using Index X

Description:

Stores one byte indirect from a register to data space. For parts with SRAM, the data space consists of the Register File,

I/O memory and internal SRAM (and external SRAM if applicable). For parts without SRAM, the data space consists of the

The data location is pointed to by the X (16 bits) Pointer Register in the Register File. Memory access is limited to the cur-

rent data segment of 64K bytes. To access another data segment in devices with more than 64K bytes data space, the

RAMPX in register in the I/O area has to be changed.

The X-pointer Register can either be left unchanged by the operation, or it can be post-incremented or pre-decremented.

These features are especially suited for accessing arrays, tables, and Stack Pointer usage of the X-pointer Register. Note

that only the low byte of the X-pointer is updated in devices with no more than 256 bytes data space. For such devices, the

high byte of the pointer is not used by this instruction and can be used for other purposes. The RAMPX Register in the I/O

area is updated in parts with more than 64K bytes data space or more than 64K bytes Program memory, and the incre-

ment/ decrement is added to the entire 24-bit address on such devices.

Not all variants of this instruction is available in all devices. Refer to the device specific instruction set summary.

The result of these combinations is undefined:

ST X+, r26

ST X+, r27

ST -X, r26

ST -X, r27

Using the X-pointer:

Operation: Comment:

(i) (X) ← Rr X: Unchanged

(ii) (X) ← Rr X ← X+1 X: Post incremented

(iii) X ← X - 1 (X) ← Rr X: Pre decremented

Syntax: Operands: Program Counter:

(i) ST X, Rr 0 ≤ r ≤ 31 PC ← PC + 1

(ii) ST X+, Rr 0 ≤ r ≤ 31 PC ← PC + 1

(iii) ST -X, Rr 0 ≤ r ≤ 31 PC ← PC + 1

16-bit Opcode :

Status Register (SREG) and Boolean Formula:

(i) 1001 001r rrrr 1100

(ii) 1001 001r rrrr 1101

(iii) 1001 001r rrrr 1110

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138 AVR Instruction Set

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Example:

clr r27 ; Clear X high byte

ldi r26,$60 ; Set X low byte to $60

st X+,r0 ; Store r0 in data space loc. $60(X post inc)

st X,r1 ; Store r1 in data space loc. $61

ldi r26,$63 ; Set X low byte to $63

st X,r2 ; Store r2 in data space loc. $63

st -X,r3 ; Store r3 in data space loc. $62(X pre dec)

Words: 1 (2 bytes)

Cycles: 2

139

AVR Instruction Set

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ST (STD) – Store Indirect From Register to Data Space using Index Y

Description:

Stores one byte indirect with or without displacement from a register to data space. For parts with SRAM, the data space

consists of the Register File, I/O memory and internal SRAM (and external SRAM if applicable). For parts without SRAM,

the data space consists of the Register File only. The EEPROM has a separate address space.

The data location is pointed to by the Y (16 bits) Pointer Register in the Register File. Memory access is limited to the cur-

rent data segment of 64K bytes. To access another data segment in devices with more than 64K bytes data space, the

RAMPY in register in the I/O area has to be changed.

The Y-pointer Register can either be left unchanged by the operation, or it can be post-incremented or pre-decremented.

These features are especially suited for accessing arrays, tables, and Stack Pointer usage of the Y-pointer Register. Note

that only the low byte of the Y-pointer is updated in devices with no more than 256 bytes data space. For such devices, the

high byte of the pointer is not used by this instruction and can be used for other purposes. The RAMPY Register in the I/O

area is updated in parts with more than 64K bytes data space or more than 64K bytes Program memory, and the incre-

ment/ decrement/displacement is added to the entire 24-bit address on such devices.

Not all variants of this instruction is available in all devices. Refer to the device specific instruction set summary.

The result of these combinations is undefined:

ST Y+, r28

ST Y+, r29

ST -Y, r28

ST -Y, r29

Using the Y-pointer:

Operation: Comment:

(i) (Y) ← Rr Y: Unchanged

(ii) (Y) ← Rr Y ← Y+1 Y: Post incremented

(iii) Y ← Y - 1 (Y) ← Rr Y: Pre decremented

(iiii) (Y+q) ← Rr Y: Unchanged, q: Displacement

Syntax: Operands: Program Counter:

(i) ST Y, Rr 0 ≤ r ≤ 31 PC ← PC + 1

(ii) ST Y+, Rr 0 ≤ r ≤ 31 PC ← PC + 1

(iii) ST -Y, Rr 0 ≤ r ≤ 31 PC ← PC + 1

(iiii) STD Y+q, Rr 0 ≤ r ≤ 31, 0 ≤ q ≤ 63 PC ← PC + 1

16-bit Opcode:

(i) 1000 001r rrrr 1000

(ii) 1001 001r rrrr 1001

(iii) 1001 001r rrrr 1010

(iiii) 10q0 qq1r rrrr 1qqq

140 AVR Instruction Set

0856E–AVR–11/05

Status Register (SREG) and Boolean Formula:

Example:

clr r29 ; Clear Y high byte

ldi r28,$60 ; Set Y low byte to $60

st Y+,r0 ; Store r0 in data space loc. $60(Y post inc)

st Y,r1 ; Store r1 in data space loc. $61

ldi r28,$63 ; Set Y low byte to $63

st Y,r2 ; Store r2 in data space loc. $63

st -Y,r3 ; Store r3 in data space loc. $62(Y pre dec)

std Y+2,r4 ; Store r4 in data space loc. $64

Words: 1 (2 bytes)

Cycles: 2

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ST (STD) – Store Indirect From Register to Data Space using Index Z

Description:

Stores one byte indirect with or without displacement from a register to data space. For parts with SRAM, the data space

consists of the Register File, I/O memory and internal SRAM (and external SRAM if applicable). For parts without SRAM,

the data space consists of the Register File only. The EEPROM has a separate address space.

The data location is pointed to by the Z (16 bits) Pointer Register in the Register File. Memory access is limited to the cur-

rent data segment of 64K bytes. To access another data segment in devices with more than 64K bytes data space, the

RAMPZ in register in the I/O area has to be changed.

The Z-pointer Register can either be left unchanged by the operation, or it can be post-incremented or pre-decremented.

These features are especially suited for Stack Pointer usage of the Z-pointer Register, however because the Z-pointer

Register can be used for indirect subroutine calls, indirect jumps and table lookup, it is often more convenient to use the X

or Y-pointer as a dedicated Stack Pointer. Note that only the low byte of the Z-pointer is updated in devices with no more

than 256 bytes data space. For such devices, the high byte of the pointer is not used by this instruction and can be used for

other purposes. The RAMPZ Register in the I/O area is updated in parts with more than 64K bytes data space or more than

64K bytes Program memory, and the increment/decrement/displacement is added to the entire 24-bit address on such

devices.

Not all variants of this instruction is available in all devices. Refer to the device specific instruction set summary.

The result of these combinations is undefined:

ST Z+, r30

ST Z+, r31

ST -Z, r30

ST -Z, r31

Using the Z-pointer:

Operation: Comment:

(i) (Z) ←Rr Z: Unchanged

(ii) (Z) ← Rr Z ← Z+1 Z: Post incremented

(iii) Z ← Z - 1 (Z) ← Rr Z: Pre decremented

(iiii) (Z+q) ← Rr Z: Unchanged, q: Displacement

Syntax: Operands: Program Counter:

(i) ST Z, Rr 0 ≤ r ≤ 31 PC ← PC + 1

(ii) ST Z+, Rr 0 ≤ r ≤ 31 PC ← PC + 1

(iii) ST -Z, Rr 0 ≤ r ≤ 31 PC ← PC + 1

(iiii) STD Z+q, Rr 0 ≤ r ≤ 31, 0 ≤ q ≤ 63 PC ← PC + 1

142 AVR Instruction Set

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16-bit Opcode :

Status Register (SREG) and Boolean Formula:

Example:

clr r31 ; Clear Z high byte

ldi r30,$60 ; Set Z low byte to $60

st Z+,r0 ; Store r0 in data space loc. $60(Z post inc)

st Z,r1 ; Store r1 in data space loc. $61

ldi r30,$63 ; Set Z low byte to $63

st Z,r2 ; Store r2 in data space loc. $63

st -Z,r3 ; Store r3 in data space loc. $62(Z pre dec)

std Z+2,r4 ; Store r4 in data space loc. $64

Words: 1 (2 bytes)

Cycles: 2

(i) 1000 001r rrrr 0000

(ii) 1001 001r rrrr 0001

(iii) 1001 001r rrrr 0010

(iiii) 10q0 qq1r rrrr 0qqq

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STS – Store Direct to Data Space

Description:

Stores one byte from a Register to the data space. For parts with SRAM, the data space consists of the Register File, I/O

memory and internal SRAM (and external SRAM if applicable). For parts without SRAM, the data space consists of the

A 16-bit address must be supplied. Memory access is limited to the current data segment of 64K bytes. The STS instruction

uses the RAMPD Register to access memory above 64K bytes. To access another data segment in devices with more than

64K bytes data space, the RAMPD in register in the I/O area has to be changed.

This instruction is not available in all devices. Refer to the device specific instruction set summary.

Operation:

(i) (k) ← Rr

Syntax: Operands: Program Counter:

(i) STS k,Rr 0 ≤ r ≤ 31, 0 ≤ k ≤ 65535 PC ← PC + 2

32-bit Opcode:

Status Register (SREG) and Boolean Formula:

Example:

lds r2,$FF00 ; Load r2 with the contents of data space location $FF00

add r2,r1 ; add r1 to r2

sts $FF00,r2 ; Write back

Words: 2 (4 bytes)

Cycles: 2

1001 001d dddd 0000

kkkk kkkk kkkk kkkk

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SUB – Subtract without Carry

Description:

Subtracts two registers and places the result in the destination register Rd.

Operation:

(i) Rd ← Rd - Rr

Syntax: Operands: Program Counter:

(i) SUB Rd,Rr 0 ≤ d ≤ 31, 0 ≤ r ≤ 31 PC ← PC + 1

16-bit Opcode:

Status Register and Boolean Formula:

H: Rd3• Rr3 +Rr3 •R3 +R3• Rd3

Set if there was a borrow from bit 3; cleared otherwise

S: N ⊕ V, For signed tests.

V: Rd7• Rr7 •R7 +Rd7 •Rr7• R7

Set if two’s complement overflow resulted from the operation; cleared otherwise.

N: R7

Set if MSB of the result is set; cleared otherwise.

Z: R7• R6 •R5• R4• R3 •R2• R1• R0

Set if the result is $00; cleared otherwise.

C: Rd7• Rr7 +Rr7 •R7 +R7• Rd7

Set if the absolute value of the contents of Rr is larger than the absolute value of Rd; cleared otherwise.

R (Result) equals Rd after the operation.

Example:

sub r13,r12 ; Subtract r12 from r13

brne noteq ; Branch if r12<>r13

...

noteq: nop ; Branch destination (do nothing)

Words: 1 (2 bytes)

Cycles: 1

0001 10rd dddd rrrr

ITHSVNZC

––⇔⇔⇔⇔⇔⇔

145

AVR Instruction Set

0856E–AVR–11/05

SUBI – Subtract Immediate

Description:

Subtracts a register and a constant and places the result in the destination register Rd. This instruction is working on Reg-

ister R16 to R31 and is very well suited for operations on the X, Y and Z-pointers.

Operation:

(i) Rd ← Rd - K

Syntax: Operands: Program Counter:

(i) SUBI Rd,K 16 ≤ d ≤ 31, 0 ≤ K ≤ 255 PC ← PC + 1

16-bit Opcode:

Status Register and Boolean Formula:

H: Rd3• K3+K3 •R3 +R3 •Rd3

Set if there was a borrow from bit 3; cleared otherwise

S: N ⊕ V, For signed tests.

V: Rd7• K7 •R7 +Rd7• K7 •R7

Set if two’s complement overflow resulted from the operation; cleared otherwise.

N: R7

Set if MSB of the result is set; cleared otherwise.

Z: R7• R6 •R5• R4• R3 •R2• R1• R0

Set if the result is $00; cleared otherwise.

C: Rd7• K7 +K7 •R7 +R7• Rd7

Set if the absolute value of K is larger than the absolute value of Rd; cleared otherwise.

R (Result) equals Rd after the operation.

Example:

subi r22,$11 ; Subtract $11 from r22

brne noteq ; Branch if r22<>$11

...

noteq: nop ; Branch destination (do nothing)

Words: 1 (2 bytes)

Cycles: 1

0101 KKKK dddd KKKK

ITHSVNZC

––⇔⇔⇔⇔⇔⇔

146 AVR Instruction Set

0856E–AVR–11/05

SWAP – Swap Nibbles

Description:

Swaps high and low nibbles in a register.

Operation:

(i) R(7:4) ← Rd(3:0), R(3:0) ← Rd(7:4)

Syntax: Operands: Program Counter:

(i) SWAP Rd 0 ≤ d ≤ 31 PC ← PC + 1

16-bit Opcode:

Status Register and Boolean Formula:

R (Result) equals Rd after the operation.

Example:

inc r1 ; Increment r1

swap r1 ; Swap high and low nibble of r1

inc r1 ; Increment high nibble of r1

swap r1 ; Swap back

Words: 1 (2 bytes)

Cycles: 1

1001 010d dddd 0010

ITHSVNZC

––––––––

147

AVR Instruction Set

0856E–AVR–11/05

TST – Test for Zero or Minus

Description:

Tests if a register is zero or negative. Performs a logical AND between a register and itself. The register will remain

unchanged.

Operation:

(i) Rd ← Rd • Rd

Syntax: Operands: Program Counter:

(i) TST Rd 0 ≤ d ≤ 31 PC ← PC + 1

16-bit Opcode: (see AND Rd, Rd)

Status Register and Boolean Formula:

S: N ⊕ V, For signed tests.

V: 0

Cleared

N: R7

Set if MSB of the result is set; cleared otherwise.

Z: R7• R6 •R5• R4• R3 •R2• R1• R0

Set if the result is $00; cleared otherwise.

R (Result) equals Rd.

Example:

tst r0 ; Test r0

breq zero ; Branch if r0=0

...

zero: nop ; Branch destination (do nothing)

Words: 1 (2 bytes)

Cycles: 1

0010 00dd dddd dddd

ITHSVNZC

–– –⇔0⇔⇔ –

148 AVR Instruction Set

0856E–AVR–11/05

WDR – Watchdog Reset

Description:

This instruction resets the Watchdog Timer. This instruction must be executed within a limited time given by the WD pres-

caler. See the Watchdog Timer hardware specification.

Operation:

(i) WD timer restart.

Syntax: Operands: Program Counter:

(i) WDR None PC ← PC + 1

16-bit Opcode:

Status Register and Boolean Formula:

Example:

wdr ; Reset watchdog timer

Words: 1 (2 bytes)

Cycles: 1

1001 0101 1010 1000

ITHSVNZC

––––––––

149

AVR Instruction Set

0856E–AVR–11/05

Printed on recycled paper.

0856E–AVR–11/05

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