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DS28E01-100
1K-Bit Protected 1-Wire EEPROM with
SHA-1 Engine
Abridged Data Sheet
GENERAL DESCRIPTION
The DS28E01-100 combines 1024 bits of EEPROM
with challenge-and-response authentication security
implemented with the ISO/IEC 10118-3 Secure Hash
Algorithm (SHA-1). The 1024-bit EEPROM array is
configured as four pages of 256 bits with a 64-bit
scratchpad to perform write operations. All memory
pages can be write protected, and one page can be
put in EPROM-emulation mode, where bits can only
be changed from a 1 to a 0 state. Each DS28E01-
100 has its own guaranteed unique 64-bit ROM
registration number that is factory lasered into the
chip. The DS28E01-100 communicates over the
single-contact 1-Wire® bus. The communication
follows the standard Dallas Semiconductor 1-Wire
protocol with the registration number acting as node
address in the case of a multi-device 1-Wire network.
APPLICATIONS
Printer Cartridge Configuration and Monitoring
Medical Sensor Authentication and Calibration
System Intellectual Property Protection
TYPICAL OPERATING CIRCUIT
µC
IO
DS28E01
GND
RPUP
VCC
FEATURES
1024 bits of EEPROM memory partitioned into
four pages of 256 bits
On-chip 512-bit SHA-1 engine to com pute 160-bit
Message Authentication Codes (MAC) and to
generate secrets
Write access requires knowledge of the secret
and the capability of computing and transmitting
a 160-bit MAC as authorization
User-programmable page write-protecti on for
page 0, page 3 or all four pages togethe r
User-programmable OTP EPROM emulation
mode for page 1 ("write to 0")
Communicates to host with a single digital signal
at 15.3k bits or 125k bits per second using
1-Wire protocol
Switchpoint Hysteresis and Filtering to Optimize
Performance in the Presence of Noi se
Reads and writes over a wide voltage range of
2.8V to 5.25V from -40°C to +85°C
6-lead TSOC, 2-lead SFN or solder-bumped
chipscale surface mo unt package
ORDERING INFORMATION
PART TEMP RANGE PIN-PACKAGE
DS28E01P-100 -40°C to 85°C 6-pin TSOC
DS28E01P-100/T&R -40°C to 85°C TSOC Tape & reel
DS28E01P-100+ -40°C to 85°C 6-pin TSOC
DS28E01P-100+T&R -40°C to 85°C TSOC Tape & reel
DS28E01G-100+T&R -40°C to 85°C 2-pin SFN Tape &
reel
+ Indicates lead-free compliance.
Ordering Information and Pin Configuration continued
at the end of the data sheet.
Request full data shee t at:
www.maxim-ic.com/fullds/DS28E01-100
PIN CONFIGURATION
TSO C 150 mil
Top view
6 NC
5 NC
4 NC
GND 1
IO 2
NC 3
www.maxim-ic.com
Commands, Registers, an d Modes are capitalized for
clarity.
1-Wire is a registered trademark of Dallas Semiconductor Corp.
Abridged Data Sheet DS28E01-100
2 of 16
ABSOLUTE MAXIMUM RATINGS
IO Voltage to GND -0.5V, +6V
IO Sink Current 20mA
Operating Temperature Range -40°C to +85°C
Junction Temperature +150°C
Storage Temperature Range -55°C to +125°C
Soldering Temperature See IPC/JEDEC J-STD-020A
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only,
and functional operation of the device at these or any other conditions beyond thos e indicated in the operational sections of the specifications is
not implied. Exposure to the absolute maximum rating conditions for extended periods may affect device reliability.
ELECTRICAL CHARACTERISTICS (TA = -40°C to +85°C; see Note 1.)
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
IO PIN GENERAL DATA
1-Wire Pullup Voltage VPUP (Note 2) 2.8 5.25 V
1-Wire Pullup Resistance RPUP (Notes 2, 3) 0.3 2.2
kΩ
Input Capacitance CIO (Notes 4, 5) 1000 pF
Input Load Current ILIO pin at VPUP 0.05 6.7 µA
High-to-Low Switching
Threshold VTL (Notes 5, 6, 7) 0.46 VPUP -
1.8V V
Input Low Voltage VIL (Notes 2, 8) 0.5 V
Low-to-High Switching
Threshold VTH (Notes 5, 6, 9) 1.0 VPUP -
1.1V V
Switching Hysteresis VHY (Notes 5, 6, 10) 0.21 1.70 V
Output Low Voltage VOL At 4mA Current Load (Note 11) 0.4 V
Standard speed, RPUP = 2.2kΩ 5
Overdrive speed, RPUP = 2.2kΩ 2
Recovery Time
(Notes 2, 12) tREC Overdrive speed, directl y prior to reset
pulse; RPUP = 2.2kΩ 5
µs
Standard speed 0.5 5.0 Rising-Edge Hold-off Time
(Notes 5, 13) tREH Overdrive speed Not applicable (0) µs
Standard speed 65 Time slot Duration
(Note 2, 14) tSLOT Overdrive speed 8 µs
IO PIN, 1-WIRE RESET, PRESENCE DETECT CYCLE
Standard speed 480 640
Reset Low Time (Note 2) tRSTL Overdrive speed 48 80 µs
Standard speed 15 60 Presence Detect High
Time tPDH Overdrive speed 2 6
µs
Standard speed 60 240 Presence Detect Low
Time tPDL Overdrive speed 8 24 µs
Standard speed 60 75 Presence Detect Sample
Time (Notes 2, 15) tMSP Overdrive speed 6 10 µs
IO PIN, 1-Wire WRITE Standard speed 60 120
Overdrive speed, VPUP > 4.5V 5 15.5
Write-0 Low Time
(Notes 2, 16, 17) tW0L Overdrive speed 6 15.5 µs
Standard speed 1 15 Write-1 Low Time
(Notes 2, 17) tW1L Overdrive speed 1 2
µs
IO PIN, 1-Wire READ Standard speed 5 15 - δ Read Low Time
(Notes 2, 18) tRL Overdrive speed 1 2 - δ µs
Standard speed tRL + δ 15
Read Sample Time
(Notes 2, 18) tMSR Overdrive speed tRL + δ 2
µs
Abridged Data Sheet DS28E01-100
3 of 16
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
EEPROM
Programming Current IPROG (Notes 5, 19) 0.8 mA
Programming Time tPROG (Note 20) 10 ms
At 25°C 200k Write/Erase Cycles (En-
durance) (Notes 21, 22) NCY At 85°C (worst case) 50k ---
Data Retention
(Notes 23, 24, 25) tDR At 85°C (worst case) 40 years
SHA-1 ENGINE
SHA Computation Current
(Notes 5, 19) ILCSHA See full version of data sheet . mA
SHA Computation Ti me
(Note 5) tCSHA See full version of data sheet. ms
Note 1: Specifications at TA = -40°C are guaranteed by design only and not production-tested.
Note 2: System requirement.
Note 3: Maximum allowable pullup resistance is a function of the number of 1-Wire devices in the system and 1-Wire recovery times. The
specified value here applies to systems with only one device and with the minimum 1-Wire recovery times. For more heavily
loaded systems, an active pullup such as that found in the DS2482-x00, DS2480B, o r DS2490 may be required.
Note 4: Maximum value represents the internal parasite capacitance when VPUP is first applied. If RPUP = 2.2kΩ, 2.5µs after V PUP has been
applied the parasite capacitance will not affect normal communications.
Note 5: Guaranteed by design, characterization and/or simulation only. Not production tested.
Note 6: VTL, VTH, and VHY are a function of the internal supply voltage, which is itself a function of VPUP, RPUP, 1-Wire timing, and capacitive
loading on IO. Lower VPUP, higher RPUP, shorter tREC, and heavier capacitive loading all lead to lower values of VTL, VTH, and VHY.
Note 7: Voltage below which, during a falling edge on IO, a logic 0 is detected.
Note 8: The voltage on IO needs to be less than or equal to VIL(MAX) at all times the master is driving IO to a logic-0 level.
Note 9: Voltage above which, during a rising edge on IO, a logic 1 is detected.
Note 10: After VTH is crossed during a rising edge on IO, the voltage on IO has to drop by at least VHY to be detected as logic '0'.
Note 11: The I-V characteristic is linear for voltages less than 1V.
Note 12: Applies to a single device attached to a 1-Wire line.
Note 13: The earliest recognition of a negative edge is possible at tREH after VTH has been reached on the preceding rising edge.
Note 14: Defines maximum possible bit rate. Equal to tW0L(min) + tREC(min).
Note 15: Interval after tRSTL during which a bus master is guaranteed to sample a logic-0 on IO if there is a DS 28E01-100 present.
Minimum limit is tPDH(max); maximum limit is tPDH(min) + tPDL(min).
Note 16: Highlighted numbers are NO T in compliance with legacy 1-Wire product standards. See comparison table below.
Note 17: ε in Figure 12 represents the time required for the pullup circuitry to pull the voltage on IO up from VIL to VTH. The actual maximum
duration for the master to pull the line low is tW1Lmax + tF - ε and tW0Lmax + tF - ε respectively.
Note 18: δ in Figure 12 represents the time required for the pullup circuitry to pull the voltage on IO up from VIL to the input high threshold
of the bus master. The actual maximum duration for the master to pull the line low is tRLmax + tF.
Note 19: Current drawn from IO during EEPROM programming or SHA-1 computation interval.
Note 20: See full version of data sheet.
Note 21: Write-cycle endurance is degraded as TA increases.
Note 22: Not 100% production-tested; guaranteed by reliability monitor sampling.
Note 23: Data retention is degraded as TA increases.
Note 24: Guaranteed by 100% production test at elevated temperature for a shorter time; equivalence of this production test to data sheet
limit at operating temperature range is established by reliability testing.
Note 25: EEPROM writes may become non-functional after the data retention time is exceeded. Long-time storage at elevated
temperatures is not recommended; the device may lose its write-capability after 10 years at 125°C or 40 years at 85°C.
Abridged Data Sheet DS28E01-100
4 of 16
LEGACY VALUES DS28E01-100 VALUES
PARAMETER STANDARD SPEED OVERDRIVE SPEED STANDARD SPEED OVERDRIVE SPEED
MIN MAX MIN MAX MIN MAX MIN MAX
tSLOT (incl. tREC) 61µs (undef.) 7µs (undef.) 65µs1) (undef.) 8µs1) (undef.)
tRSTL 480µs (undef.) 48µs 80µs 480µs 640µs 48µs 80µs
tPDH 15µs 60µs 2µs 6µs 15µs 60µs 2µs 6µs
tPDL 60µs 240µs 8µs 24µs 60µs 240µs 8µs 24µs
tW0L 60µs 120µs 6µs 16µs 60µs 120µs 6µs 15.5µs
1) Intentional change, longer recovery time requirement due to modified 1-Wire f ront end.
PIN DESCRIPTION
NAME FUNCTION
IO 1-Wire bus interface. Open drain, requires external pull-up resistor .
GND Ground reference
NC Not connected
DESCRIPTION
The DS28E01-100 combines 1024 bits of EEPROM organized as four 256-bit pages, a 64-bit secret, a register
page, a 512-bit SHA-1 engine, a 64-bit ROM registration number in a single chip. Data is transferred serially
through the 1-Wire protocol, which requires only a single data lead and a ground return. The DS28E01-100 has an
additional memory area called the scratchpad that acts as a buffer when writing to the memory, the register page,
or when installing a new secret. Data is first written to the scratchpad from where it can be read back. After the data
has been verified, a copy scratchpad command transfers the data to its final memory location, provided that the
DS28E01-100 receives a matching 160-bit MAC. The computation of the MAC involves the secret and additional
data stored in the DS28E01-100 including the device’s registration number. Only a new secret can be loaded
without providing a MAC. The SHA-1 engine is also activated to compute 160-bit MACs when performing an
authenticated read of a memory page and when computing a new secret, instead of loading it.
The DS28E01-100 understands a unique command "Refresh Scratchpad." Proper use of a refresh sequence after
a copy scratchpad operation reduces the number of weak bit failures if the device is used in a touch environment
(see the Writing with Verification section). The refresh sequence also provides a means to restore functionality in a
device with bits in a weak state.
The device's 64-bit ROM registration number guarantees unique identification and is used to address the device in
a multidrop 1-Wire network environment, where multiple devices reside on a common 1-Wire bus and operate
independently of each other. Applications of the DS28E01-100 include printer cartridge configuration and
monitoring, medical sensor authentication and calibration, and system intellectu al prop erty protection.
OVERVIEW
The block diagram in Figure 1 shows the relationships between the major control and memory sections of the
DS28E01-100. The DS28E01-100 has six main data components: 1) 64-bit lasered ROM, 2) 64-bit scratchpad, 3)
four 256-bit pages of EEPROM, 4) register page, 5) 64-bit secrets memory, and 6) a 512-bit SHA-1 (Secure Hash
Algorithm) engine. The hierarchical structure of the 1-Wire protocol is shown in Figure 2. The bus master must first
provide one of the seven ROM function commands, 1) Read ROM, 2) Match ROM, 3) Search ROM, 4) Skip ROM,
5) Resume Communication, 6) Overdrive-Skip ROM, or 7) Overdrive-Match ROM. Upon completion of an overdrive
ROM command byte executed at standard speed, the device enters overdrive mode where all subsequent commu-
nication occurs at a higher speed. The protocol required for these ROM function commands is described in Figure
10. After a ROM function command is successfully executed, the memory and SHA-1 functions become accessible
and the master can provide any one of the 9 available function commands. The function protocols are described in
Figure 8*. All data is read and written least significant bit first.
* For Figure 8 see the full version of the data sheet.
Abridged Data Sheet DS28E01-100
5 of 16
Figure 1. Block Diagram
PARASITE POWER
1-Wire net
64-bit
Lasered ROM
1-Wire
Function Control
Secrets Memory
64 bits
64-bit
Scratchpad
Data Memor y
4 Pages of
256 bits each
CRC16
Generator
Memory and
SHA Function
Control Unit
512-bit
Se cure Hash
Algorithm
Engine
Register Page
Figure 2. Hierarchical Structure for 1-Wire Protocol
DS28E01-100
Available
Commands:
Command
Level: Data Field
Affected:
1-Wire ROM Function
Commands (see Figure 10)
Device-specific
Memory Function
Commands (see Figure 8)
Read ROM
Match ROM
Search ROM
Skip ROM
Resume
Overdrive Skip
Overdrive Matc h
64-bit Reg. #, RC-Flag
64-bit Reg. #, RC-Flag
64-bit Reg. #, RC-Flag
RC-Flag
RC-Flag
RC-Flag, OD-Flag
64-bit Reg. #, RC-Flag, OD-Flag
For details see the full
version of the data sheet.
Abridged Data Sheet DS28E01-100
6 of 16
64-BIT LASERED ROM
Each DS28E01-100 has a unique ROM Registration Number that is 64 bits long, as shown in Figure 3. The first
eight bits are a 1-Wire family code. The next 48 bits are a unique serial number. The last eight bits are a CRC
(Cyclic Redundancy Check) of the first 56 bits. The 1-Wire CRC is generated using a polynomial generator
consisting of a shift register and XOR gates as shown in Figure 4. The polynomial is X8 + X5 + X4 + 1. Additional
information about the Dallas 1-Wire CRC is available in Application Note 27. The shift register bits are initialized to
zero. Then starting with the LSB of the family code, one bit at a time is shifted in. After the 8th bit of the family code
has been entered, then the serial number is entered. After the 48th bit of the serial number has been entered, the
shift register contains the CRC value. Shifting in the eight bits of CRC should return the shift register to all zeros.
Figure 3. 64-Bit LASERED ROM
MSB LSB
8-Bit CRC Code 48-Bit Serial Number 8-Bit Family Code*
MSB LSB MSB LSB MSB LSB
Figure 4. 1-Wire CRC Generator
X0X1X2X3X4X5X6X7X8
Polynomial = X8 + X5 + X4 + 1
1st
STAGE 2nd
STAGE 3rd
STAGE 4th
STAGE 6th
STAGE
5th
STAGE 7th
STAGE 8th
STAGE
INPUT DATA
MEMORY
The DS28E01-100 has four memory areas: data memory, secrets memory, register page with special function
registers and user-bytes, and a volatile scratchpad. The data memory is organized as four pages of 32 bytes.
Secret and scratchpad are 8 bytes each. The scratchpad acts as a buffer when writing to the data memory, loading
the initial secret or when writing to the register page. For further details (including Figures 5 and 6) refer to the full
version of the data sheet.
* For the actual Family Code refer to the full version of the data sheet.
Abridged Data Sheet DS28E01-100
7 of 16
ADDRESS REGISTERS AND TRANSFER STATUS
The DS28E01-100 employs three address registers: TA1, TA2, and E/S (Figure 7). These registers are common to
many other 1-Wire devices but operate slightly differently with the DS28E01-100. Registers TA1 and TA2 must be
loaded with the target address to which the data is written or from which data is read. Register E/S is a read-only
transfer-status register, used to verify data integrity with write commands. Since the scratchpad of the DS28E01-
100 is designed to accept data in blocks of eight bytes only, the lower three bits of TA1 are forced to 0 and the
lower three bits of the E/S register (ending offset) always read 1. This indicates that all the data in the scratchpad is
used for a subsequent copying into main memory or secret. Bit 5 of the E/S register, called PF or partial byte flag,
is a logic-1 if the number of data bits sent by the master is not an integer multiple of eight or if the data in the
scratchpad is not valid due to a loss of power. A valid write to the scratchpad clears the PF bit. Bits 3, 4, and 6
have no function; they always read 1. The partial flag supports the master checking the data integrity after a write
command. The highest valued bit of the E/S register is called the AA or authorization accepted flag, which indicates
that the data stored in the scratchpad has already been copied to the target memory address. Writing data to the
scratchpad clears this flag.
Figure 7. Address Registers
Bit # 7 6 5 4 3 2 1 0
Target Address (TA1) T7 T6 T5 T4 T3 T2
(0) T1
(0) T0
(0)
Target Address (TA2) T15 T14 T13 T12 T11 T10 T9 T8
Ending Address with
Data Status (E/S)
(Read Only) AA 1 PF 1 1 E2
(1) E1
(1) E0
(1)
WRITING WITH VERIFICATION
To write data to the DS28E01-100, the scratchpad has to be used as intermediate storage. First the master issues
the write scratchpad command, whi ch sp ecifies the desired target address and the data to be written to the scratch-
pad. Note that writes to data memory must be performed on 8-byte boundaries with the three LSBs of the target
address T2–T0 equal to 000b. Therefore, if T2–T0 are sent with non-zero values, the device sets these bits to zero
and uses the modified address as the target address. The master should always send eight complete data bytes.
After the eight bytes of data have been transmitted, the master can elect to receive an inverted CRC16 of the write
scratchpad command, the address as sent by the master, and the data as sent by the master. The master can
compare the CRC to the value it has calculated itself in order to determine if the communication was successful.
After the scratchpad has been written, the master should always perform a read scratchpad to verify that the
intended data was in fact written. During a read scratchpad, the DS28E01-100 repeats the target address TA1 and
TA2 and sends the contents of the E/S register. The partial flag (bit 5 of the E/S register) is set to 1 if the last data
byte the DS28E01-100 received during a write scratchpad or refresh scratchpad command was incomplete, or if
there was a loss of power since data was last written to the scratchpad. The authorization-accepted (AA) flag (bit 7
of the E/S register) is normally cleared by a write scratchpad or refresh scratchpad; therefore, if it is set to 1, it indi-
cates that the DS28E01-100 did not understand the proceeding write (or refresh) scratchpad command. In either of
these cases, the master should rewrite the scratchpad. After the master receives the E/S register, the scratchpad
data is received. The descriptions of write scratchpad and refresh scratchpad provide clarification of what changes
can occur to the scratchpad data under certain conditions. An inverted CRC of the read scratchpad command, tar-
get address, E/S register, and scratchpad data follows the scratchpad data. As with the write scratchpad command,
this CRC can be compared to the value the master has calculated itself in order to determine if the communication
was successful. After the master has verified the data, it can send the copy scratchpad to copy the scratchpad to
memory. Alternatively, the load first secret or compute next secret command can be issued to change the secret.
See the descriptions of these commands for more information.
Abridged Data Sheet DS28E01-100
8 of 16
MEMORY AND SHA FUNCTION COMMANDS
This section describes the commands and flow charts to use the memory and SHA-1 engine of the device. It
includes Tables 1 to 4 and Figure 8. Please refer to the full version of the data sheet.
SHA-1 COMPUTATION ALGORITHM
This description of the SHA computation is adapted from the Secure Hash Standard SHA-1 document that can be
downloaded from the NIST website (www.itl.nist.gov/fipspubs/fip180-1.htm). Further details are found in the full
version of the data sheet.
1-Wire BUS SYSTEM
The 1-Wire bus is a system that has a single bus master and one or more slaves. In all instances the DS28E01-
100 is a slave device. The bus master is typically a microcontroller. The discussion of this bus system is broken
down into three topics: hardware configuration, transaction sequence, and 1-Wire signaling (signal types and
timing). The 1-Wire protocol defines bus transactions in terms of the bus state during specific time slots, which are
initiated on the falling edge of sync pulse s from the bus master.
HARDWARE CONFIGURATION
The 1-Wire bus has only a single line by definition; it is important that each device on the bus be able to drive it at
the appropriate time. To facilitate this, each device attached to the 1-Wire bus must have open-drain or tri-state
outputs. The 1-Wire port of the DS28E01-100 is open drain with an internal circuit equivalent to that shown in
Figure 9.
A multidrop bus consists of a 1-Wire bus with multiple slaves attached. The DS28E01-100 supports both a Stan-
dard and Overdrive communication speed of 15.3kbps (max) and 125kbps (max), respectively. Note that legacy 1-
Wire products support a standard communication speed of 16.3kbps and Overdrive of 142kbps. The slightly
reduced rates for the DS28E01-100 are a result of additional recovery times, which in turn were driven by a 1-Wire
physical interface enhancement to improve noise immunity. The value of the pullup resistor primarily depends on
the network size and load conditions. The DS28E01-100 requires a pullup resistor of 2.2kΩ (max) at any speed.
The idle state for the 1-Wire bus is high. If for any reason a transaction needs to be suspended, the bus MUST be
left in the idle state if the transaction is to resume. If this does not occur and the bus is left low for more than 16µs
(Overdrive speed) or more than 120µ s (standard speed), one or more devices on the bus may be reset.
Figure 9. Hardware Configuration
Open Drain
Port Pin
RX = RECEIVE
TX = TRANSMIT 100 Ω
MOSFET
VPUP
RX
TX TX
RX
DATA
RPUP
IL
BUS MASTER DS28E01 1-Wire PORT
Abridged Data Sheet DS28E01-100
9 of 16
TRANSACTION SEQUENCE
The protocol for accessing the DS28E01-100 th rough the 1-Wire port is as follows:
Initialization
ROM Function Command
Memory/SHA Function Command
Transaction/Data
INITIALIZATION
All transactions on the 1-Wire bus begin with an initialization sequence. The initialization sequence consists of a
reset pulse transmitted by the bus master followed by presence pulse(s) transmitted by the slave(s). The presence
pulse lets the bus master know that the DS28E01-100 is on the bus and is ready to operate. For more details, see
the 1-Wire Signaling section.
1-Wire ROM FUNCTION COMMANDS
Once the bus master has detected a presence, it can issue one of the seven ROM function commands that the
DS28E01-100 supports. All ROM function commands are 8 bits long. A list of these commands follows (refer to the
flow chart in Figure 10).
READ ROM [33h]
This command allows the bus master to read the DS28E01-100’s 8-bit family code, unique 48-bit serial number,
and 8-bit CRC. This command can only be used if there is a single slave on the bus. If more than one slave is
present on the bus, a data collision occurs when all slaves try to transmit at the same time (open drain produces a
wired-AND re sult). The resultant family code and 48-bit serial number result in a mismatch of the CRC.
MATCH ROM [55h]
The Match ROM command, followed by a 64-bit ROM sequence, allows the bus master to address a specific
DS28E01-100 on a multidrop bus. Only the DS28E01-100 that exactly matches the 64-bit ROM sequence,
including the external address, responds to the following Memory/Control Function command. All other slaves wait
for a reset pulse. This comm and can be used with a single or multiple devices on the bus.
SEARCH ROM [F0h]
When a system is initially brought up, the bus master might not know the number of devices on the 1-Wire bus or
their device ID numbers. By taking advantage of the wired-AND property of the bus, the master can use a process
of elimination to identify the device ID numbers of all slave devices. For each bit of the device ID number, starting
with the least significant bit, the bus master issues a triplet of time slots. On the first slot, each slave device
participating in the search outputs the true value of its device ID number bit. On the second slot, each slave device
participating in the search outputs the complemented value of its device ID number bit. On the third slot, the master
writes the tr ue value of the bit to be selected. All slave devices that do not match the bit written by the master stop
participating in the search. If both of the read bits are zero, the master knows that slave devices exist with both
states of the bit. By choosing which state to write, the bus master branches in the ROM code tree. After one
complete pass, the bus master knows the device ID number of a single device. Additional passes identify the
device ID numbers of the remaining devices. Refer to Application Note 187: 1-Wire Search Algorithm for a detailed
discussion, includi ng an example.
SKIP ROM [CCh]
This command can save time in a single-drop bus system by allowing the bus master to access the memory
functions without providing the 64-bit ROM code. If more than one slave is present on the bus and, for example, a
read command is issued following the Skip ROM command, data collision occurs on the bus as multiple slaves
transmit simultaneously (open-drain pulldowns produce a wired-A ND result).
Abridged Data Sheet DS28E01-100
10 of 16
Figure 10-1. ROM Functions Flow Chart
From Figure 10
2nd Part
To Mem ory Functions
Flow Chart (Figure 8)
Master TX Bit 0
Master TX Bit 63
Master TX Bit 1
Bit 63
Match ?
RC = 0
DS28E01 TX Bit 0
DS28E01 TX Bit 0
Master TX Bit 0
DS28E01 TX Bit 1
DS28E01 TX Bit 1
Master TX Bit 1
DS28E01 TX Bit 63
DS28E01 TX Bit 63
Master TX Bit 63
RC = 1
Bit 1
Match ?
Bit 0
Match ? Y
N
Y
N
Y
N
Bit 63
Match ?
RC = 0
RC = 1
Bit 1
Match ?
Bit 0
Match ? Y
N
Y
N
Y
N
RC = 0
DS28E01 TX
CRC Byte
DS28E01 TX
Serial Number
(6 Bytes)
DS28E01 TX
Family Code
(1 Byte)
RC = 0
To Figure 10
2nd Part
N
F0h
Search RO M
Command ?
N
55h
Match ROM
Command ? N
CCh
Skip ROM
Command ?
YY Y Y
N
33h
Read ROM
Command ?
To Figure 10
2nd Part
From Memory Functions
Flow Chart (Figur e 8)
Bus Master TX ROM
Function Command DS28E01 TX
Presence Pu lse
OD
Reset Pulse ? N
Y
OD = 0
Bus Master TX
Reset Pulse From Figure 10, 2n
d
Par
t
Abridged Data Sheet DS28E01-100
11 of 16
Figure 10-2. ROM Functions Flow Chart (continued)
To Figure 10
1st Part
From Figure 10
1st Part
From Figure 10
1st Part
To Figure 10, 1s
t
Part
Y
N
A5h
Resume
Command ?
RC = 1 ?
Y
N
3Ch
Overdrive
Skip ROM ?
RC = 0 ; OD = 1
Master
TX Reset ? Y
N
N
Y
Master
TX Reset ?
N
Y
Master TX Bit 0
Master TX Bit 63
Master TX Bit 1
Bit 63
Match ?
RC = 0 ; OD = 1
RC = 1
Bit 1
Match ?
Y
N
Y
N
Bit 0
Match ?
Y
N
Y
N
69h
Overdrive Match
ROM ?
Abridged Data Sheet DS28E01-100
12 of 16
RESUME [A5h]
To maximize the data throughput in a multidrop environment, the Resume function is available. This function
checks the status of the RC bit and, if it is set, directly transfers control to the Memory functions, similar to a Skip
ROM command. The only way to set the RC bit is through successfully executing the Match ROM, Search ROM, or
Overdrive Match ROM command. Once the RC bit is set, the device can repeatedly be accessed through the
Resume Command function. Accessing another device on the bus clears the RC bit, preventing two or more
devices from simultaneousl y responding to the Resume Command function.
OVERDRIVE SKIP ROM [3Ch]
On a single-drop bus this command can save time by allowing the bus master to access the memory functions
without providing the 64-bit ROM code. Unlike the normal Skip ROM command, the Overdrive Skip ROM sets the
DS28E01-100 in the Overdrive mode (OD = 1). All communication following this command has to occur at
Overdrive speed until a reset pulse of minimum 480µs duration resets all devices on the bus to standard speed
(OD = 0).
When issued on a multidrop bus, this command sets all Overdrive-supporting devices into Overdrive mode. To
subsequently address a specific Overdrive-supporting device, a reset pulse at Overdrive speed has to be issued
followed by a Match ROM or Search ROM command sequence. This speeds up the time for the search process. If
more than one slave supporting Overdrive is present on the bus and the Overdrive Skip ROM command is followed
by a Read command, data collision occurs on the bus as multiple slaves transmit simultaneously (open-drain
pulldowns produce a wire d-AND result).
OVERDRIVE MATCH ROM [69h]
The Overdrive Match ROM command followed by a 64-bit ROM sequence transmitted at Overdrive Speed allows
the bus master to address a specific DS28E01-100 on a multidrop bus and to simultaneously set it in Overdrive
mode. Only the DS28E01-100 that exactly matches the 64-bit ROM sequence responds to the subsequent Memory
or SHA Function command. Slaves already in Overdrive mode from a previous Overdrive Skip or successful
Overdrive Match command remain in Overdrive mode. All overdrive-capable slaves return to standard speed at the
next Reset Pulse of minimum 480µs duration. The Overdrive Match ROM command can be used with a single or
multiple devices on the bus.
1-Wire SIGNALING
The DS28E01-100 requires strict protocols to ensure data integrity. The protocol consists of four types of signaling
on one line: Reset Sequence with Reset Pulse and Presence Pulse, Write-Zero, Write-One, and Read-Data.
Except for the Presence pulse, the bus master initiates all falling edges. The DS28E01-100 can communicate at
two different speeds, standard speed, and Overdrive Speed. If not explicitly set into the Overdrive mode, the
DS28E01-100 comm unicates at standard speed. While in Overdrive Mode the fa st timing applies to all waveforms.
To get from idle to active, the voltage on the 1-Wire line needs to fall from VPUP below the threshold VTL. To get
from active to idle, the voltage needs to rise from VILMAX past the threshold VTH. The time it takes for the voltage to
make this rise is seen in Figure 11 as 'ε' and its duration depends on the pullup resistor (RPUP) used and the
capacitance of the 1-Wire network attached. The voltage VILMAX is relevant for the DS28E01-100 when determining
a logical level, not triggering any events.
Figure 11 shows the initialization sequence required to begin any communication with the DS28E01-100. A Reset
Pulse followed by a Presence Pulse indicates the DS28E01-100 is ready to receive data, given the correct ROM
and Memory/Control Function command. If the bus master uses slew-rate control on the falling edge, it must pull
down the line for tRSTL + tF to compensate for the edge. A tRSTL duration of 480µs or longer exits the Overdrive
Mode, returning the device to standard speed. If the DS28E01-100 is in Overdrive Mode and tRSTL is no longer than
80µs, the device remains in Overdrive Mode. If the device is in Overdrive Mode and tRSTL is between 80µs and
480µs, the device will reset , but the communication speed is undetermined.
Abridged Data Sheet DS28E01-100
13 of 16
Figure 11. Initialization Procedure: Reset and Presence Pulse
RESISTOR MASTER DS28E01
tRSTL tPDL
tRSTH
tPDH
MASTER TX “RESET PULSE” MASTER RX “ PRESENCE PULSE”
VPUP
VIHMASTER
VTH
VTL
VILMAX
0V
ε
tFtREC
tMSP
After the bus master has released the line it goes into receive mode. Now the 1-Wire bus is pulled to VPUP through
the pullup resistor, or in case of a DS2482-x00 or DS2480B driver, by active circuitry. When the threshold VTH is
crossed, the DS28E01-100 waits for tPDH and then transmits a Presence Pulse by pulling the line low for tPDL. To
detect a presence pulse, the master must test the logical state of the 1-Wire line at tMSP.
The tRSTH window must be at least the sum of tPDHMAX, tPDLMAX, and tRECMIN. Immediately after tRSTH is expired, the
DS28E01-100 is ready for data communication. In a mixed population network, tRSTH should be extended to
minimum 480µs at standard spe ed and 48µs at Overdrive speed to accommodate other 1-Wire devices.
Read/Write Time Sl ots
Data communication with the DS28E01-100 takes place in time slots, which carry a single bit each. Write-time slots
transport data from bus master to slave. Read-time slots transfer data from slave to master. Figure 12 illustrates
the definitions of the write- and read-time slots.
All communication begins with the master pulling the data line low. As the voltage on the 1-Wire line falls below the
threshold VTL, the DS28E01-100 starts its internal timing generator that determines when the data line is sampled
during a write-time slot and how long data is valid during a read-time slot.
Figure 12. Read/Write Timing Diagram
Write-One Time Slot
RESISTOR MASTER
VPUP
VIHMASTER
VTH
VTL
VILMAX
0V tFtSLOT
tW1L
ε
Abridged Data Sheet DS28E01-100
14 of 16
Figure 12. Read/Write Timing Diagram (continued)
Write-Zero Time Slot
RESISTOR MASTER
tREC
VPUP
VIHMASTER
VTH
VTL
VILMA
X
0V tFtSLOT
tW0L
ε
Read-Data Time Slot
RESISTOR MASTER DS28E01
tREC
VPUP
VIHMASTER
VTH
VTL
VILMAX
0V
Master
Sampling
Window
δ
tFtSLOT
tRL tMSR
Master-to-Slave
For a write-one time slot, the voltage on the data line must have crossed the VTH threshold before the write-one
low time tW1LMAX is expired. For a write-zero time slot, the voltage on the data line must stay below the VTH
threshold until the write-zero low time tW0LMIN is expired. For the most reliable communication, the voltage on the
data line should not exceed VILMAX during the entire tW0L or tW1L window. After the VTH threshold has been crossed,
the DS28E01-100 needs a recovery time tREC before it is ready for the next time slot.
Slave-to-Master
A read-data time slot begins like a write-one time slot. The voltage on the data line must remain below VTL until the
read low time tRL is expired. During the tRL window, when responding with a 0, the DS28E01-100 starts pulling the
data line low; its internal timing generator determines when this pulldown ends and the voltage starts rising again.
When responding with a 1, the DS28E01-100 does not hold the data line low at all, and the voltage starts rising as
soon as tRL is over.
The sum of tRL + δ (rise time) on one side and the internal timing generator of the DS28E01-100 on the other side
define the master sampling window (tMSRMIN to tMSRMAX) in which the master must perform a read from the data line.
For the most reliable communication, tRL should be as short as permissible, and the master should read close to
but no later than tMSRMAX. After reading from the data line, the master must wait until tSLOT is expired. This
guarantees sufficient recovery time tREC for the DS28E01-100 to get ready for the next time slot. Note that tREC
specified herein applies only to a single DS28E01-100 attached to a 1-Wire line. For multidevice configurations,
tREC needs to be extended to accommodate the additional 1-Wire device input capacitance. Alternatively, an
interface that performs active pullup during the 1-Wire recovery time such as the DS2482-x00 or DS2480B 1-Wire
line drivers can be used.
Abridged Data Sheet DS28E01-100
15 of 16
IMPROVED NETWORK BEHAVIOR (SWITCHPOINT HYSTERESIS)
In a 1-Wire environment, line termination is possible only during transients controlled by the bus master (1-Wire
driver). 1-Wire networks, therefore, are susceptible to noise of various origins. Depending on the physical size and
topology of the network, reflections from end points and branch points can add up, or cancel each other to some
extent. Such reflections are visible as glitches or ringing on the 1-Wire communication line. Noise coupled onto the
1-Wire line from external sources can also result in signal glitching. A glitch during the rising edge of a time slot can
cause a slave device to lose synchronization with the master and, consequently, result in a search ROM command
coming to a dead end or cause a device-specific function command to abort. For better performance in network
applications, the DS28E01-100 uses a new 1-Wire front end, which makes it less sensitive to noise.
The 1-Wire front end of the DS28E01-100 differs fro m traditional sla v e devices in three characteristics.
1) There is additional low-pass filtering in the circuit that detects the falling edge at the beginning of a time slot.
This reduces the sensitivity to high-frequ ency noise. This additional filtering does not apply at Overdrive speed.
2) There is a hysteresis at the low-to-high switching threshold VTH. If a negative glitch crosses VTH but does not go
below VTH - VHY, it will not be recognized (Figu re 13, Case A). Th e hystere sis is effective at any 1-Wire speed.
3) There is a time window specified by the rising edge hold-off time tREH during which glitches are ignored, even if
they extend below VTH - VHY threshold (Figure 13, Case B, tGL < tREH). Deep voltage droops or glitches that
appear late after crossing the VTH threshold and extend beyond the tREH window cannot be filtered out and are
taken as the beginning of a new time sl ot (Figure 13, Case C, tGL tREH).
Devices that have the parameters VHY, and tREH specified in their electrical characteristics use the improved 1-Wire
front end.
Figure 13. Noise Suppression Scheme
VPUP
VTH
VHY
0V
tREH
tGL
tREH
tGL
Case A Case CCase B
CRC GENERATION
With the DS28E01-100 there are two different types of CRCs. One CRC is an 8-bit type. It is computed at the
factory and is stored in the most significant byte of the 64-bit ROM. The equivalent polynomial function of this CRC
is X8 + X5 + X4 + 1. To determine whether the ROM data has been read without error the bus master can compute
the CRC value from the first 56 bits of the 64-bit ROM and compare it to the value read from the DS28E01-100.
This 8-bit CRC is received in the true form (noninverted) when reading the ROM.
The other CRC is a 16-bit type, which is used for error detection with Memory and SHA-1 function commands. For
details (including Figu re 14) see the full version of the data sheet.
Abridged Data Sheet DS28E01-100
16 of 16
PIN CONFIGURATION (CONTINUED) PIN CONFIGURATION (CONTINUED)
µCSP*, Top View with
Laser Mark, Contacts
Not Visible.
A
2 = IO
A
3 = GND
ll Other Bumps: NC
yywwrr = Date/ Revision
###xx = Lot Number
See 21-0093, pkg. code B9-8, for package outline.
* Refer to package reliability report for important
guidelines on qualified usage conditions.
A
B
C
1 2 3
A
1 Mark
D
S28E01
yywwrr
#
##xx
Bottom View Side View
SFN, approx. 6 x 6 x 0.9 mm
1 2
SFN, pinout:
Pin 1 ------------- IO
Pin 2 ------------- GND
Package Outline Drawing 56-00SFN-000
The SFN Package is qualified for electro m echanical
contact applications only, not for soldering.
ORDERING INFORMATION
(CONTINUED)
SFN PACKAGE ORIENTATION ON
TAPE-AND-REEL
PART TEMP RANGE PIN-PACKAGE
DS28E01X-100 -40 to 85°C µCSP, 10k pcs,
Tape-and-Reel
DS28E01X-100-S -40 to 85°C µCSP, 2.5k pcs,
Tape-and-Reel
User Direction of Feed
Leads face up in orient ation shown above.
Contact factory for availability of the µCSP.
PACKAGE INFORMATION
(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information, go to
www.maxim-ic.com/DallasPackInfo.)