DS2431
1024-Bit, 1-Wire EEPROM
General Description
The DS2431 is a 1024-bit, 1-Wire® EEPROM chip organized as four memory pages of 256 bits each. Data is
written to an 8-byte scratchpad, verified, and then copied
to the EEPROM memory. As a special feature, the four
memory pages can individually be write protected or
put in EPROM-emulation mode, where bits can only be
changed from a 1 to a 0 state. The DS2431 communicates over the single-conductor 1-Wire bus. The communication follows the standard 1-Wire protocol. Each
device has its own unalterable and unique 64-bit ROM
registration number that is factory lasered into the chip.
The registration number is used to address the device in
a multidrop, 1-Wire net environment.
Applications
●●
●●
●●
●●
●●
Accessory/PCB Identification
Medical Sensor Calibration Data Storage
Analog Sensor Calibration Including IEEE P1451.4
Smart Sensors
Ink and Toner Print Cartridge Identification
After-Market Management of Consumables
Benefits and Features
●● Easily Add Traceability and Relevant Information to
Any Individual System
• 1024 Bits of EEPROM Memory Partitioned Into
Four Pages of 256 Bits
• Individual Memory Pages Can Be Permanently
Write Protected or Put in EPROM-Emulation Mode
(Write to 0)
• Switchpoint Hysteresis and Filtering to Optimize
Performance in the Presence of Noise
●● Minimalist 1-Wire Interface Lowers Cost and
Interface Complexity
• IEC 1000-4-2 Level 4 ESD Protection
(±8kV Contact, ±15kV Air, typ)
• Reads and Writes Over a Wide Voltage Range
from 2.8V to 5.25V from -40°C to +85°C
• Communicates to Host with a Single Digital Signal
at 15.4kbps or 125kbps
Ordering Information
PART
Typical Operating Circuit
VCC
RPUP
IO
µC
DS2431
GND
Pin Configurations appear at end of data sheet.
1-Wire is a registered trademark of Maxim Integrated Products, Inc.
19-4675; Rev 15; 3/15
TEMP RANGE
PIN-PACKAGE
DS2431+
-40°C to +85°C
3 TO-92
DS2431+T&R
-40°C to +85°C
3 TO-92
DS2431P+
-40°C to +85°C
6 TSOC
DS2431P+T&R
-40°C to +85°C
6 TSOC
DS2431G+U
-40°C to +85°C
2 SFN (6mm x 6mm)
DS2431G+T&R
-40°C to +85°C
2 SFN (6mm x 6mm)
(2.5k pcs)
DS2431GA+U
-40°C to +85°C
2 SFN (3.5mm x 6.5mm)
DS2431GA+T&R
-40°C to +85°C
2 SFN (3.5mm x 6.5mm)
(2.5k pcs)
DS2431Q+T&R
-40°C to +85°C
6 TDFN-EP* (2.5k pcs)
DS2431X-S+
-40°C to +85°C
3x3 UCSPR (2.5k pcs)
DS2431X+
-40°C to +85°C
3x3 UCSPR (10k pcs)
Note: The leads of TO-92 packages on tape and reel are
formed to approximately 100-mil (2.54mm) spacing. For details,
refer to the package outline drawing.
+Denotes a lead(Pb)-free/RoHS-compliant package.
T&R = Tape and reel.
*EP = Exposed pad.
DS2431
1024-Bit, 1-Wire EEPROM
Absolute Maximum Ratings
IO Voltage Range to GND........................................-0.5V to +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
Lead Temperature (excluding UCSP, soldering, 10s).......+300°C
Soldering Temperature (reflow)
TO-92............................................................................+250°C
AIl other packages, excluding SFN...............................+260°C
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 those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect
device reliability.
Electrical Characteristics
(TA = -40°C to +85°C.) (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
IL
IO pin at VPUP
0.05
6.7
µA
High-to-Low Switching Threshold
VTL
(Notes 5, 6, 7)
0.5
VPUP 1.8
V
Input Low Voltage
VIL
(Notes 2, 8)
0.5
V
Low-to-High Switching Threshold
VTH
(Notes 5, 6, 9)
1.0
VPUP 1.0
V
Switching Hysteresis
VHY
(Notes 5, 6, 10)
0.21
1.70
V
Output Low Voltage
VOL
At 4mA (Note 11)
0.4
V
Recovery Time
(Notes 2,12)
tREC
Rising-Edge Hold-Off Time (Notes
5, 13)
tREH
Time Slot Duration
(Notes 2, 14)
tSLOT
Standard speed, RPUP = 2.2kΩ
5
Overdrive speed, RPUP = 2.2kΩ
2
Overdrive speed, directly prior to reset
pulse; RPUP = 2.2kΩ
5
Standard speed
Overdrive speed
0.5
µs
5.0
Not applicable (0)
Standard speed
65
Overdrive speed
8
µs
µs
IO PIN: 1-Wire RESET, PRESENCE-DETECT CYCLE
Reset Low Time (Note 2)
tRSTL
Presence-Detect High Time
tPDH
Presence-Detect Low Time
tPDL
Presence-Detect Sample Time
(Notes 2, 15)
tMSP
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Standard speed
480
640
Overdrive speed
48
80
Standard speed
15
60
Overdrive speed
2
6
Standard speed
60
240
Overdrive speed
8
24
Standard speed
60
75
Overdrive speed
6
10
µs
µs
µs
µs
Maxim Integrated │ 2
DS2431
1024-Bit, 1-Wire EEPROM
Electrical Characteristics (continued)
(TA = -40°C to +85°C.) (Note 1)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
IO PIN: 1-Wire WRITE
Write-Zero Low Time
(Notes 2, 16, 17)
Write-One Low Time
(Notes 2, 17)
tW0L
tW1L
Standard speed
60
120
Overdrive speed, VPUP > 4.5V
5
15.5
Overdrive speed
6
15.5
Standard speed
1
15
Overdrive speed
1
2
Standard speed
5
15 - d
Overdrive speed
1
2-d
Standard speed
tRL + d
15
Overdrive speed
tRL + d
2
µs
µs
IO PIN: 1-Wire READ
Read Low Time
(Notes 2, 18)
Read Sample Time
(Notes 2, 18)
tRL
tMSR
µs
µs
EEPROM
Programming Current
IPROG
(Notes 5, 19)
Programming Time
tPROG
(Notes 20, 21)
Write/Erase Cycles (Endurance)
(Notes 22, 23)
NCY
Data Retention
(Notes 24, 25, 26)
tDR
At +25°C
200k
At +85°C (worst case)
50k
At +85°C (worst case)
40
0.8
mA
10
ms
—
Years
Note 1: Limits are 100% production tested at TA = +25°C and/or TA = +85°C. Limits over the operating temperature range and relevant supply voltage range are guaranteed by design and characterization. Typical values are not guaranteed.
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, or DS2490 may be
required.
Note 4: Maximum value represents the internal parasite capacitance when VPUP is first applied. Once the parasite capacitance is
charged, it does not affect normal communication.
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 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 must be less than or equal to VILMAX 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 must 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 tW0LMIN + tRECMIN.
Note 15: Interval after tRSTL during which a bus master can read a logic 0 on IO if there is a DS2431 present. The power-up presence detect pulse could be outside this interval, but will be complete within 2ms after power-up.
Note 16: Numbers in bold are not in compliance with legacy 1-Wire product standards. See the Comparison Table.
Note 17: ε in Figure 11 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 11 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.
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Maxim Integrated │ 3
DS2431
1024-Bit, 1-Wire EEPROM
Note 19: Current drawn from IO during the EEPROM programming interval. The pullup circuit on IO during the programming interval
should be such that the voltage at IO is greater than or equal to VPUPMIN. If VPUP in the system is close to VPUPMIN, a
low-impedance bypass of RPUP, which can be activated during programming, may need to be added.
Note 20: Interval begins tREHMAX after the trailing rising edge on IO for the last time slot of the E/S byte for a valid Copy
Scratchpad sequence. Interval ends once the device’s self-timed EEPROM programming cycle is complete and the current
drawn by the device has returned from IPROG to IL.
Note 21: tPROG for units branded version “A1” is 12.5ms. tPROG for units branded version “A2” and later is 10ms.
Note 22: Write-cycle endurance is degraded as TA increases.
Note 23: Not 100% production tested; guaranteed by reliability monitor sampling.
Note 24: Data retention is degraded as TA increases.
Note 25: Guaranteed by 100% production test at elevated temperature for a shorter time; equivalence of this production test to the
data sheet limit at operating temperature range is established by reliability testing.
Note 26: EEPROM writes can become nonfunctional after the data-retention time is exceeded. Long-term storage at elevated temperatures is not recommended; the device can lose its write capability after 10 years at +125°C or 40 years at +85°C.
Comparison Table
PARAMETER
LEGACY VALUES
STANDARD SPEED (µs)
MIN
MAX
tSLOT (including tREC)
61
tRSTL
480
tPDH
DS2431 VALUES
OVERDRIVE SPEED
(µs)
MIN
MAX
(undefined)
7
(undefined)
48
15
60
tPDL
60
tW0L
60
STANDARD SPEED (µs)
MIN
MAX
(undefined)
65*
80
480
2
6
240
8
120
6
OVERDRIVE SPEED
(µs)
MIN
MAX
(undefined)
8*
(undefined)
640
48
80
15
60
2
6
24
60
240
8
24
16
60
120
6
15.5
*Intentional change; longer recovery time requirement due to modified 1-Wire front-end.
Note: Numbers in bold are not in compliance with legacy 1-Wire product standards.
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Maxim Integrated │ 4
DS2431
1024-Bit, 1-Wire EEPROM
Pin Description
PIN
NAME
TSOC
TO-92
TDFN-EP
SFN
UCSPR
3, 4, 5, 6
3
1, 4, 5, 6
—
A2, A3, C2,
C3
N.C.
2
2
2
1
C1
IO
1
1
3
2
A1
GND
—
—
—
—
—
EP
FUNCTION
Not Connected
1-Wire Bus Interface. Open-drain signal
that requires an external pullup resistor.
Ground Reference
Exposed Pad (TDFN only). Solder
evenly to the board’s ground plane for
proper operation. Refer to Application
Note 3273: Exposed Pads: A Brief
Introduction for additional information.
Detailed Description
The DS2431 combines 1024 bits of EEPROM, an 8-byte
register/control page with up to 7 user read/write bytes,
and a fully featured 1-Wire interface in a single chip. Each
DS2431 has its own 64-bit ROM registration number that
is factory lasered into the chip to provide a guaranteed
unique identity for absolute traceability. Data is transferred
serially through the 1-Wire protocol, which requires only a
single data lead and a ground return. The DS2431 has an
additional memory area called the scratchpad that acts as
a buffer when writing to the main memory or the register
page. Data is first written to the scratchpad from which it
can be read back. After the data has been verified, a Copy
Scratchpad command transfers the data to its final memory
location. The DS2431 applications include accessory/PCB
identification, medical sensor calibration data storage,
analog sensor calibration including IEEE P1451.4 smart
sensors, ink and toner print cartridge identification, and
after-market management of consumables.
Overview
The block diagram in Figure 1 shows the relationships
between the major control and memory sections of the
DS2431. The DS2431 has four main data components:
64-bit lasered ROM, 64-bit scratchpad, four 32-byte
pages of EEPROM, and a 64-bit register page.
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PARASITE POWER
IO
1-Wire
FUNCTION CONTROL
64-BIT
LASERED ROM
DS2431
MEMORY
FUNCTION
CONTROL UNIT
CRC-16
GENERATOR
DATA MEMORY
4 PAGES OF
256 BITS EACH
64-BIT
SCRATCHPAD
REGISTER PAGE
64 BITS
Figure 1. Block Diagram
Maxim Integrated │ 5
DS2431
1024-Bit, 1-Wire EEPROM
AVAILABLE COMMANDS: DATA FIELD AFFECTED:
DS2431 COMMAND LEVEL:
1-Wire ROM FUNCTION COMMANDS
(SEE FIGURE 9)
DS2431-SPECIFIC
MEMORY FUNCTION COMMANDS
(SEE FIGURE 7)
READ ROM
MATCH ROM
SEARCH ROM
SKIP ROM
RESUME
OVERDRIVE-SKIP ROM
OVERDRIVE-MATCH ROM
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
WRITE SCRATCHPAD
READ SCRATCHPAD
COPY SCRATCHPAD
READ MEMORY
64-BIT SCRATCHPAD, FLAGS
64-BIT SCRATCHPAD
DATA MEMORY, REGISTER PAGE
DATA MEMORY, REGISTER PAGE
Figure 2. Hierarchical Structure for 1-Wire Protocol
MSB
LSB
8-BIT
CRC CODE
MSB
8-BIT FAMILY CODE
(2Dh)
48-BIT SERIAL NUMBER
LSB MSB
LSB MSB
LSB
Figure 3. 64-Bit Lasered ROM
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: Read ROM, Match
ROM, Search ROM, Skip ROM, Resume, Overdrive-Skip
ROM, or Overdrive-Match ROM. Upon completion of an
Overdrive-Skip ROM or Overdrive-Match ROM command
byte executed at standard speed, the device enters overdrive mode where all subsequent communication occurs
at a higher speed. The protocol required for these ROM
function commands is described in Figure 9. After a ROM
function command is successfully executed, the memory
functions become accessible and the master can provide
any one of the four memory function commands. The protocol for these memory function commands is described
in Figure 7. All data is read and written least significant bit first.
64-Bit Lasered ROM
Each DS2431 contains a unique ROM code that is 64 bits
long. The first 8 bits are a 1-Wire family code. The next 48
bits are a unique serial number. The last 8 bits are a cyclic
redundancy check (CRC) of the first 56 bits. See Figure 3
for details. 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 1-Wire CRC is available
in Application Note 27: Understanding and Using Cyclic
Redundancy Checks with Maxim iButton® Products.
The shift register bits are initialized to 0. Then, starting
with the least significant bit of the family code, one bit at
a time is shifted in. After the 8th bit of the family code has
been entered, the serial number is entered. After the last
bit of the serial number has been entered, the shift register contains the CRC value. Shifting in the 8 bits of the
CRC returns the shift register to all 0s.
iButton is a registered trademark of Maxim Integrated Products, Inc.
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Maxim Integrated │ 6
DS2431
1024-Bit, 1-Wire EEPROM
POLYNOMIAL = X8 + X5 + X4 + 1
1ST
STAGE
X0
2ND
STAGE
X1
3RD
STAGE
X2
4TH
STAGE
X3
5TH
STAGE
6TH
STAGE
X4
X5
7TH
STAGE
X6
8TH
STAGE
X7
X8
INPUT DATA
Figure 4. 1-Wire CRC Generator
Memory Access
Data memory and registers are located in a linear address
space, as shown in Figure 5. The data memory and the
registers have unrestricted read access. The DS2431
EEPROM array consists of 18 rows of 8 bytes each.
The first 16 rows are divided equally into four memory
pages (32 bytes each). These four pages are the primary
data memory. Each page can be individually set to open
(unprotected), write protected, or EPROM mode by set-
ting the associated protection byte in the register row. As
a factory default, the entire data memory is unprotected
and its contents are undefined. The last two rows contain
protection registers and reserved bytes. The register row
consists of 4 protection control bytes, a copy-protection
byte, the factory byte, and 2 user byte/manufacture ID
bytes. The manufacturer ID can be a customer-supplied
identification code that assists the application software
in identifying the product the DS2431 is associated with.
ADDRESS RANGE
TYPE
0000h to 001Fh
R/(W)
Data Memory Page 0
DESCRIPTION
—
PROTECTION CODES
0020h to 003Fh
R/(W)
Data Memory Page 1
—
0040h to 005Fh
R/(W)
Data Memory Page 2
—
0060h to 007Fh
R/(W)
Data Memory Page 3
—
0080h*
R/(W)
Protection Control Byte Page 0
55h: Write Protect P0; AAh: EPROM Mode P0;
55h or AAh: Write Protect 80h
0081h*
R/(W)
Protection Control Byte Page 1
55h: Write Protect P1; AAh: EPROM Mode P1;
55h or AAh: Write Protect 81h
0082h*
R/(W)
Protection Control Byte Page 2
55h: Write Protect P2; AAh: EPROM Mode P2;
55h or AAh: Write Protect 82h
0083h*
R/(W)
Protection Control Byte Page 3
55h: Write Protect P3; AAh: EPROM Mode P3;
55h or AAh: Write Protect 83h
0084h*
R/(W)
Copy Protection Byte
55h or AAh: Copy Protect 0080h:008Fh, and Any
Write-Protected Pages
0085h
R
Factory Byte. Set at Factory.
AAh: Write Protect 85h, 86h, 87h;
55h: Write Protect 85h; Unprotect 86h, 87h
0086h
R/(W)
User Byte/Manufacturer ID
—
0087h
R/(W)
User Byte/Manufacturer ID
—
0088h to 008Fh
—
Reserved
—
*Once programmed to AAh or 55h this address becomes read only. All other codes can be stored, but neither write protect
the address nor activate any function.
Figure 5. Memory Map
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Maxim Integrated │ 7
DS2431
1024-Bit, 1-Wire EEPROM
Contact the factory to set up and register a custom manufacturer ID. The last row is reserved for future use. It is
undefined in terms of R/W functionality and should not
be used.
The copy-protection byte is used for a higher level of
security and should only be used after all other protection
control bytes, user bytes, and write-protected pages are
set to their final value. If the copy-protection byte is set
to 55h or AAh, all copy attempts to the register row and
user-byte row are blocked. In addition, all copy attempts
to write-protected main memory pages (i.e., refresh) are
blocked.
In addition to the main EEPROM array, an 8-byte volatile
scratchpad is included. Writes to the EEPROM array are
a two-step process. First, data is written to the scratchpad
and then copied into the main array. This allows the user
to first verify the data written to the scratchpad prior to
copying into the main array. The device only supports full
row (8-byte) copy operations. For data in the scratchpad
to be valid for a copy operation, the address supplied with
a Write Scratchpad command must start on a row boundary, and 8 full bytes must be written into the scratchpad.
Address Registers and Transfer Status
The DS2431 employs three address registers: TA1, TA2,
and E/S (Figure 6). These registers are common to many
other 1-Wire devices but operate slightly differently with
the DS2431. 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 transferstatus register used to verify data integrity with write commands. E/S bits E[2:0] are loaded with the incoming T[2:0]
on a Write Scratchpad command and increment on each
subsequent data byte. This is, in effect, a byte-ending offset counter within the 8-byte scratchpad. Bit 5 of the E/S
register, called PF, is a logic 1 if the data in the scratchpad
is not valid due to a loss of power or if the master sends
fewer bytes than needed to reach the end of the scratchpad. For a valid write to the scratchpad, T[2:0] must be 0
and the master must have sent 8 data bytes. Bits 3, 4, and
6 have no function; they always read 0. The highest valued bit of the E/S register, called authorization accepted
(AA), acts as a flag to indicate that the data stored in the
scratchpad has already been copied to the target memory
address. Writing data to the scratchpad clears this flag.
The protection control registers determine how incoming data on a Write Scratchpad command is loaded into
the scratchpad. A protection setting of 55h (write protect)
causes the incoming data to be ignored and the target
address main memory data to be loaded into the scratchpad. A protection setting of AAh (EPROM mode) causes
the logical AND of incoming data and target address
main memory data to be loaded into the scratchpad. Any
other protection control register setting leaves the associated memory page open for unrestricted write access.
Note: For the EPROM mode to function, the entire
affected memory page must first be programmed to FFh.
Protection-control byte settings of 55h or AAh also write
protect the protection-control byte. The protection-control
byte setting of 55h does not block the copy. This allows
write-protected data to be refreshed (i.e., reprogrammed
with the current data) in the device.
7
6
5
4
3
2
1
0
TARGET ADDRESS (TA1)
T7
T6
T5
T4
T3
T2
T1
T0
TARGET ADDRESS (TA2)
T15
T14
T13
T12
T11
T10
T9
T8
ENDING ADDRESS WITH
DATA STATUS (E/S)
(READ ONLY)
AA
0
PF
0
0
E2
E1
E0
BIT #
Figure 6. Address Registers
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Maxim Integrated │ 8
DS2431
Writing with Verification
To write data to the DS2431, the scratchpad must be
used as intermediate storage. First, the master issues
the Write Scratchpad command to specify the desired
target address, followed by the data to be written to the
scratchpad. Note that Copy Scratchpad commands must
be performed on 8-byte boundaries, i.e., the three LSBs
of the target address (T2, T1, T0) must be equal to 000b.
If T[2:0] are sent with nonzero values, the copy function is blocked. Under certain conditions (see the Write
Scratchpad [0Fh] section) the master receives an inverted
CRC-16 of the command, address (actual address sent),
and data at the end of the Write Scratchpad command
sequence. Knowing this CRC value, the master can
compare it to the value it has calculated to decide if the
communication was successful and proceed to the Copy
Scratchpad command. If the master could not receive the
CRC-16, it should send the Read Scratchpad command to
verify data integrity. As a preamble to the scratchpad data,
the DS2431 repeats the target address TA1 and TA2 and
sends the contents of the E/S register. If the PF flag is set,
data did not arrive correctly in the scratchpad, or there was
a loss of power since data was last written to the scratchpad. The master does not need to continue reading; it can
start a new trial to write data to the scratchpad. Similarly,
a set AA flag together with a cleared PF flag indicates that
the device did not recognize the Write command.
If everything went correctly, both flags are cleared. Now
the master can continue reading and verifying every data
byte. After the master has verified the data, it can send the
Copy Scratchpad command, for example. This command
must be followed exactly by the data of the three address
registers, TA1, TA2, and E/S. The master should obtain
the contents of these registers by reading the scratchpad.
Memory Function Commands
The Memory Function Flowchart (Figure 7) describes
the protocols necessary for accessing the memory of the
DS2431. An example on how to use these functions to
write to and read from the device is in the Memory Function
Example section. The communication between the master
and the DS2431 takes place either at standard speed
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1024-Bit, 1-Wire EEPROM
(default, OD = 0) or at overdrive speed (OD = 1). If not
explicitly set into overdrive mode, the DS2431 assumes
standard speed.
Write Scratchpad [0Fh]
The Write Scratchpad command applies to the data
memory and the writable addresses in the register page.
For the scratchpad data to be valid for copying to the
array, the user must perform a Write Scratchpad command of 8 bytes starting at a valid row boundary. The
Write Scratchpad command accepts invalid addresses
and partial rows, but subsequent Copy Scratchpad commands are blocked.
After issuing the Write Scratchpad command, the master
must first provide the 2-byte target address, followed by
the data to be written to the scratchpad. The data is written to the scratchpad starting at the byte offset of T[2:0].
The E/S bits E[2:0] are loaded with the starting byte offset
and increment with each subsequent byte. Effectively,
E[2:0] is the byte offset of the last full byte written to the
scratchpad. Only full data bytes are accepted.
When executing the Write Scratchpad command, the
CRC generator inside the DS2431 (Figure 13) calculates
a CRC of the entire data stream, starting at the command
code and ending at the last data byte as sent by the master. This CRC is generated using the CRC-16 polynomial
by first clearing the CRC generator and then shifting in the
command code (0Fh) of the Write Scratchpad command,
the target addresses (TA1 and TA2), and all the data
bytes. Note that the CRC-16 calculation is performed with
the actual TA1 and TA2 and data sent by the master. The
master can end the Write Scratchpad command at any
time. However, if the end of the scratchpad is reached
(E[2:0] = 111b), the master can send 16 read time slots
and receive the CRC generated by the DS2431.
If a Write Scratchpad command is attempted to a writeprotected location, the scratchpad is loaded with the data
already existing in memory rather than the data transmitted.
Similarly, if the target address page is in EPROM mode,
the scratchpad is loaded with the bitwise logical AND of the
transmitted data and data already existing in memory.
Maxim Integrated │ 9
DS2431
1024-Bit, 1-Wire EEPROM
FROM ROM FUNCTIONS
FLOWCHART (FIGURE 9)
BUS MASTER Tx MEMORY
FUNCTION COMMAND
0Fh
WRITE SCRATCHPAD?
AAh
READ SCRATCHPAD?
N
Y
BUS MASTER Rx
TA1 (T[7:0]), TA2 (T[15:8]),
AND E/S BYTE
DS2431
SETS PF = 1
CLEARS AA = 0
SETS E[2:0] = T[2:0]
DS2431 SETS
SCRATCHPAD
BYTE COUNTER = T[2:0]
MASTER Tx DATA BYTE
TO SCRATCHPAD
MASTER Tx RESET?
APPLIES ONLY
IF THE MEMORY
AREA IS NOT
PROTECTED.
Y
N
N
E[2:0] = 7?
Y
T[2:0] = 0?
TO FIGURE 7b
Y
BUS MASTER Tx
TA1 (T[7:0]), TA2 (T[15:8])
DS2431
INCREMENTS
E[2:0]
N
N
BUS MASTER Rx
DATA BYTE FROM
SCRATCHPAD
DS2431
INCREMENTS
BYTE COUNTER
IF WRITE PROTECTED,
THE DS2431 COPIES
THE DATE BYTE FROM
THE TARGET ADDRESS
INTO THE SCRATCHPAD.
IF IN EPROM MODE,
THE DS2431 LOADS
THE BITWISE LOGICAL
AND OF THE TRANSMITTED
BYTE AND THE DATA
BYTE FROM THE TARGETED
ADDRESS INTO THE
SCRATCHPAD.
MASTER Tx RESET?
Y
N
N
BYTE COUNTER
= E[2:0]?
Y
BUS MASTER Rx CRC-16
OF COMMAND, ADDRESS,
E/S BYTE, AND DATA BYTES
AS SENT BY THE DS2431
Y
PF = 0
DS2431 Tx CRC-16 OF
COMMAND, ADDRESS,
AND DATA BYTES AS THEY
WERE SENT BY THE BUS
MASTER
BUS MASTER
Rx "1"s
N
BUS MASTER
Rx "1"s
N
MASTER Tx RESET?
Y
MASTER Tx RESET?
Y
FROM FIGURE 7b
TO ROM FUNCTIONS
FLOWCHART (FIGURE 9)
Figure 7a. Memory Function Flowchart
www.maximintegrated.com
Maxim Integrated │ 10
DS2431
FROM FIGURE 7a
1024-Bit, 1-Wire EEPROM
55h
COPY SCRATCHPAD?
Y
Y
N
BUS MASTER Tx
TA1 (T[7:0]), TA2 (T[15:8])
ADDRESS < 90h?
Y
T[15:0] < 0090h?
N
Y
APPLICABLE TO ALL R/W
MEMORY LOCATIONS.
BUS MASTER Tx
TA1 (T[7:0]), TA2 (T[15:8])
AND E/S BYTE
AUTH. CODE
MATCH?
F0h
READ MEMORY?
N
Y
N
N
N
PF = 0?
BUS MASTER Rx
DATA BYTE FROM
MEMORY ADDRESS
DS2431
INCREMENTS
ADDRESS
COUNTER
Y
Y
DS2431 SETS MEMORY
ADDRESS = (T[15:0])
COPY PROTECTED?
MASTER Tx RESET?
N
DURATION: tPROG
BUS MASTER
Rx "1"s
MASTER Tx RESET?
Y
*
N
ADDRESS < 8Fh?
N
DS2431 Tx "0"
N
BUS MASTER
Rx "1"s
N
AA = 1
DS2431 COPIES
SCRATCHPAD
DATA TO ADDRESS
Y
BUS MASTER
Rx "1"s
N
MASTER Tx RESET?
Y
MASTER Tx RESET?
Y
Y
MASTER Tx RESET?
Y
N
DS2431 Tx "1"
MASTER Tx RESET?
N
Y
TO FIGURE 7a
* 1-Wire IDLE HIGH FOR POWER.
Figure 7b. Memory Function Flowchart (continued)
www.maximintegrated.com
Maxim Integrated │ 11
DS2431
Read Scratchpad [AAh]
The Read Scratchpad command allows verifying the target address and the integrity of the scratchpad data. After
issuing the command code, the master begins reading.
The first two bytes are the target address. The next byte
is the ending offset/data status byte (E/S) followed by the
scratchpad data, which may be different from what the
master originally sent. This is of particular importance if
the target address is within the register page or a page
in either write-protection mode or EPROM mode. See the
Write Scratchpad [0Fh] section for details. The master
should read through the scratchpad (E[2:0] - T[2:0] + 1
bytes), after which it receives the inverted CRC based on
data as it was sent by the DS2431. If the master continues
reading after the CRC, all data is logic 1.
Copy Scratchpad [55h]
The Copy Scratchpad command is used to copy data
from the scratchpad to writable memory sections. After
issuing the Copy Scratchpad command, the master must
provide a 3-byte authorization pattern, which should
have been obtained by an immediately preceding Read
Scratchpad command. This 3-byte pattern must exactly
match the data contained in the three address registers
(TA1, TA2, E/S, in that order). If the pattern matches, the
target address is valid, the PF flag is not set, and the target memory is not copy protected, then the AA flag is set
and the copy begins. All 8 bytes of scratchpad contents
are copied to the target memory location. The duration
of the device’s internal data transfer is tPROG during
which the voltage on the 1-Wire bus must not fall below
2.8V. A pattern of alternating 0s and 1s are transmitted
after the data has been copied until the master issues a
reset pulse. If the PF flag is set or the target memory is
copy protected, the copy does not begin and the AA flag
is not set.
Read Memory [F0h]
The Read Memory command is the general function to
read data from the DS2431. After issuing the command,
the master must provide the 2-byte target address. After
these 2 bytes, the master reads data beginning from the
target address and can continue until address 008Fh. If
the master continues reading, the result is logic 1s. The
device’s internal TA1, TA2, E/S, and scratchpad contents
are not affected by a Read Memory command.
www.maximintegrated.com
1024-Bit, 1-Wire EEPROM
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 DS2431 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 pulses 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 threestate outputs. The 1-Wire port of the DS2431 is open drain
with an internal circuit equivalent to that shown in Figure 8.
A multidrop bus consists of a 1-Wire bus with multiple
slaves attached. The DS2431 supports both a standard
and overdrive communication speed of 15.4kbps (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 DS2431 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 DS2431 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 120μs (standard speed),
one or more devices on the bus could be reset.
Transaction Sequence
The protocol for accessing the DS2431 through the
1-Wire port is as follows:
● Initialization
● ROM Function Command
● Memory Function Command
● Transaction/Data
Maxim Integrated │ 12
DS2431
1024-Bit, 1-Wire EEPROM
VPUP
BUS MASTER
DS2431 1-Wire PORT
RPUP
DATA
Rx
Tx
OPEN-DRAIN
PORT PIN
Rx = RECEIVE
Tx = TRANSMIT
Rx
IL
Tx
100 MOSFET
Figure 8. Hardware Configuration
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 DS2431 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
DS2431 supports. All ROM function commands are 8 bits
long. A list of these commands follows (see the flowchart
in Figure 9).
Read ROM [33h]
The Read ROM command allows the bus master to read
the DS2431’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 result). 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
DS2431 on a multidrop bus. Only the DS2431 that exactly
matches the 64-bit ROM sequence responds to the subsequent memory function command. All other slaves wait
for a reset pulse. This command can be used with a single
device or multiple devices on the bus.
www.maximintegrated.com
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 registration numbers. By taking advantage
of the wired-AND property of the bus, the master can
use a process of elimination to identify the registration
numbers of all slave devices. For each bit of the registration 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 registration number bit. On the second slot,
each slave device participating in the search outputs the
complemented value of its registration number bit. On
the third slot, the master writes the true 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 registration number of a single device. Additional
passes identify the registration numbers of the remaining
devices. Refer to Application Note 187: 1-Wire Search
Algorithm for a detailed discussion, including 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-AND result).
Maxim Integrated │ 13
DS2431
1024-Bit, 1-Wire EEPROM
BUS MASTER Tx
RESET PULSE
FROM FIGURE 9b
FROM MEMORY FUNCTIONS
FLOWCHART (FIGURE 7)
OD
RESET PULSE?
N
OD = 0
Y
BUS MASTER Tx ROM
FUNCTION COMMAND
33h
READ ROM
COMMAND?
DS2431 Tx
PRESENCE PULSE
N
55h
MATCH ROM
COMMAND?
F0h
SEARCH ROM
COMMAND?
N
N
CCh
SKIP ROM
COMMAND?
Y
Y
Y
Y
RC = 0
RC = 0
RC = 0
RC = 0
DS2431 Tx
FAMILY CODE
(1 BYTE)
MASTER Tx BIT 0
DS2431 Tx BIT 0
MASTER Tx BIT 0
N
N
BIT 0 MATCH?
Y
Y
DS2431 Tx BIT 1
MASTER Tx BIT 1
DS2431 Tx BIT 1
MASTER Tx BIT 1
BIT 1 MATCH?
N
N
BIT 1 MATCH?
Y
Y
DS2431 Tx
CRC BYTE
TO FIGURE 9b
DS2431 Tx BIT 0
BIT 0 MATCH?
DS2431 Tx
SERIAL NUMBER
(6 BYTES)
N
DS2431 Tx BIT 63
MASTER Tx BIT 63
DS2431 Tx BIT 63
MASTER Tx BIT 63
BIT 63 MATCH?
N
N
BIT 63 MATCH?
Y
Y
RC = 1
RC = 1
TO FIGURE 9b
FROM FIGURE 9b
TO MEMORY FUNCTIONS
FLOWCHART (FIGURE 7)
Figure 9a. ROM Functions Flowchart
www.maximintegrated.com
Maxim Integrated │ 14
DS2431
1024-Bit, 1-Wire EEPROM
TO FIGURE 9a
FROM FIGURE 9a
A5h
RESUME
COMMAND?
3Ch
OVERDRIVESKIP ROM?
N
Y
Y
RC = 1?
N
N
Y
RC = 0; OD = 1
N
69h
OVERDRIVEMATCH ROM?
RC = 0; OD = 1
Y
MASTER Tx BIT 0
MASTER Tx
RESET?
N
Y
BIT 0 MATCH?
N
OD = 0
Y
MASTER Tx BIT 1
MASTER Tx
RESET?
N
Y
BIT 1 MATCH?
N
OD = 0
Y
MASTER Tx BIT 63
BIT 63 MATCH?
N
OD = 0
Y
FROM FIGURE 9a
RC = 1
TO FIGURE 9a
Figure 9b. ROM Functions Flowchart (continued)
www.maximintegrated.com
Maxim Integrated │ 15
DS2431
Resume [A5h]
To maximize the data throughput in a multidrop environment, the Resume command is available. This command
checks the status of the RC bit and, if it is set, directly
transfers control to the memory function commands, 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. Accessing another device on the
bus clears the RC bit, preventing two or more devices from
simultaneously responding to the Resume command.
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 command
sets the DS2431 into the overdrive mode (OD = 1). All
communication following this command must 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 must 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 (opendrain pulldowns produce a wired-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 DS2431 on a multidrop bus and to simultaneously set it in overdrive mode.
Only the DS2431 that exactly matches the 64-bit ROM
sequence responds to the subsequent memory function
command. Slaves already in overdrive mode from a previous Overdrive-Skip ROM or successful Overdrive-Match
ROM command remain in overdrive mode. All overdrivecapable 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 device or multiple devices on the bus.
www.maximintegrated.com
1024-Bit, 1-Wire EEPROM
1-Wire Signaling
The DS2431 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 DS2431 can communicate at two different speeds:
standard speed and overdrive speed. If not explicitly set
into the overdrive mode, the DS2431 communicates at
standard speed. While in overdrive mode, the fast 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 10 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 DS2431 when determining a
logical level, not triggering any events.
Figure 10 shows the initialization sequence required to
begin any communication with the DS2431. A reset pulse
followed by a presence pulse indicates that the DS2431
is ready to receive data, given the correct ROM and memory 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 DS2431 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
resets, but the communication speed is undetermined.
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 the case of a DS2482-x00
or DS2480B driver, through the active circuitry. When the
threshold VTH is crossed, the DS2431 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 DS2431 is ready for data communication. In a mixed population network, tRSTH should be
extended to minimum 480μs at standard speed and 48μs
at overdrive speed to accommodate other 1-Wire devices.
Maxim Integrated │ 16
DS2431
1024-Bit, 1-Wire EEPROM
MASTER Tx "RESET PULSE"
MASTER Rx "PRESENCE PULSE"
ε
tMSP
VPUP
VIHMASTER
VTH
VTL
VILMAX
0V
tRSTL
tPDH
tF
tPDL
tREC
tRSTH
RESISTOR
MASTER
DS2431
Figure 10. Initialization Procedure: Reset and Presence Pulse
Read/Write Time Slots
Data communication with the DS2431 takes place in time
slots that 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 11 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 DS2431 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.
Master-to-Slave
For a write-one time slot, the voltage on the data line
must have crossed the VTH threshold before the writeone 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 DS2431 needs a recovery time tREC before
it is ready for the next time slot.
www.maximintegrated.com
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 DS2431 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 DS2431 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 DS2431 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 DS2431
to get ready for the next time slot. Note that tREC specified herein applies only to a single DS2431 attached to a
1-Wire line. For multidevice configurations, tREC must 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.
Maxim Integrated │ 17
DS2431
1024-Bit, 1-Wire EEPROM
WRITE-ONE TIME SLOT
tW1L
VPUP
VIHMASTER
VTH
VTL
VILMAX
0V
ε
tF
tSLOT
RESISTOR
MASTER
WRITE-ZERO TIME SLOT
tW0L
VPUP
VIHMASTER
VTH
VTL
VILMAX
0V
ε
tF
tSLOT
RESISTOR
READ-DATA TIME SLOT
tRL
VPUP
VIHMASTER
VTH
VTL
VILMAX
0V
tREC
MASTER
tMSR
MASTER
SAMPLING
WINDOW
δ
tF
tSLOT
RESISTOR
MASTER
tREC
DS2431
Figure 11. Read/Write Timing Diagrams
www.maximintegrated.com
Maxim Integrated │ 18
DS2431
1024-Bit, 1-Wire EEPROM
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 DS2431 uses a new 1-Wire
front-end, which makes it less sensitive to noise.
The DS2431’s 1-Wire front-end differs from traditional
slave devices in three characteristics.
(Figure 12, Case B, tGL < tREH). Deep voltage drops
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 slot (Figure 12, Case C, tGL ≥ tREH).
Devices that have the parameters VHY and tREH specified in their electrical characteristics use the improved
1-Wire front-end.
CRC Generation
The DS2431 uses two different types of CRCs. One CRC
is an 8-bit type and is stored in the most significant byte
of the 64-bit ROM. The bus master can compute a CRC
value from the first 56 bits of the 64-bit ROM and compare
it to the value stored within the DS2431 to determine if the
ROM data has been received error-free. The equivalent
polynomial function of this CRC is X8 + X5 + X4 + 1. This
8-bit CRC is received in the true (noninverted) form. It is
computed at the factory and lasered into the ROM.
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 is not recognized
(Figure 12, Case A). The hysteresis is effective at any
1-Wire speed.
The other CRC is a 16-bit type, generated according to
the standardized CRC-16 polynomial function X16 + X15
+ X2 + 1. This CRC is used for fast verification of a data
transfer when writing to or reading from the scratchpad. In
contrast to the 8-bit CRC, the 16-bit CRC is always communicated in the inverted form. A CRC generator inside
the DS2431 chip (Figure 13) calculates a new 16-bit CRC,
as shown in the command flowchart (Figure 7). The bus
master compares the CRC value read from the device to
the one it calculates from the data and decides whether to
continue with an operation or to reread the portion of the
data with the CRC error.
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 the VTH - VHY threshold
With the Write Scratchpad command, the CRC is generated by first clearing the CRC generator and then shifting
in the command code, the target addresses TA1 and TA2,
1) There is additional lowpass filtering in the circuit that
detects the falling edge at the beginning of a time slot.
This reduces the sensitivity to high-frequency noise.
This additional filtering does not apply at overdrive
speed.
tREH
VPUP
VTH
tREH
VHY
CASE A
0V
CASE B
tGL
CASE C
tGL
Figure 12. Noise Suppression Scheme
www.maximintegrated.com
Maxim Integrated │ 19
DS2431
1024-Bit, 1-Wire EEPROM
POLYNOMIAL = X16 + X15 + X2 + 1
1ST
STAGE
3RD
STAGE
2ND
STAGE
X0
X2
X1
9TH
STAGE
X8
4TH
STAGE
10TH
STAGE
X9
11TH
STAGE
X10
X3
12TH
STAGE
X11
5TH
STAGE
6TH
STAGE
X4
13TH
STAGE
X12
X5
14TH
STAGE
X13
7TH
STAGE
X6
8TH
STAGE
X7
15TH
STAGE
X14
16TH
STAGE
X15
X16
CRC OUTPUT
INPUT DATA
Figure 13. CRC-16 Hardware Description and Polynomial
and all the data bytes as they were sent by the bus master. The DS2431 transmits this CRC only if E[2:0] = 111b.
With the Read Scratchpad command, the CRC is generated by first clearing the CRC generator and then shifting
in the command code, the target addresses TA1 and TA2,
the E/S byte, and the scratchpad data as they were sent
by the DS2431. The DS2431 transmits this CRC only if
the reading continues through the end of the scratchpad.
For more information on generating CRC values, refer to
Application Note 27.
Command-Specific 1-Wire Communication Protocol—Legend
SYMBOL
DESCRIPTION
RST
1-Wire reset pulse generated by master.
PD
1-Wire presence pulse generated by slave.
Select
Command and data to satisfy the ROM function protocol.
WS
Command “Write Scratchpad.”
RS
Command “Read Scratchpad.”
CPS
Command “Copy Scratchpad.”
RM
Command “Read Memory.”
TA
Target address TA1, TA2.
TA-E/S
Target address TA1, TA2 with E/S byte.
Transfer of as many bytes as needed to reach the end of the scratchpad for a given target address.
Transfer of as many data bytes as are needed to reach the end of the memory.
CRC-16
Transfer of an inverted CRC-16.
FF Loop
Indefinite loop where the master reads FF bytes.
AA Loop
Indefinite loop where the master reads AA bytes.
Programming
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Data transfer to EEPROM; no activity on the 1-Wire bus permitted during this time.
Maxim Integrated │ 20
DS2431
1024-Bit, 1-Wire EEPROM
Command-Specific 1-Wire Communication Protocol—Color Codes
Master to Slave
Slave to Master
Programming
1-Wire Communication Examples
Write Scratchpad (Cannot Fail)
RST PD Select WS
TA
CRC-16
FF Loop
Read Scratchpad (Cannot Fail)
RST
PD
Select
RS TA-E/S
CRC-16
FF Loop
Copy Scratchpad (Success)
RST PD
Select
CPS
TA-E/S
Programming
AA Loop
Copy Scratchpad (Invalid Address or PF = 1 or Copy Protected)
RST
PD
Select
CPS
TA-E/S
FF Loop
Read Memory (Success)
RST PD Select RM TA
FF Loop
Read Memory (Invalid Address)
RST
PD
Select
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RM
TA
FF Loop
Maxim Integrated │ 21
DS2431
1024-Bit, 1-Wire EEPROM
Memory Function Example
Write to the first 8 bytes of memory page 1. Read the
entire memory.
With only a single DS2431 connected to the bus master,
the communication looks like this:
MASTER MODE
DATA (LSB FIRST)
Tx
(Reset)
COMMENTS
Rx
(Presence)
Tx
CCh
Issue “Skip ROM” command
Tx
0Fh
Issue “Write Scratchpad” command
Tx
20h
TA1, beginning offset = 20h
Tx
00h
TA2, address = 0020h
Tx
Rx
Tx
(Reset)
Rx
(Presence)
Tx
CCh
Issue “Skip ROM” command
Tx
AAh
Issue “Read Scratchpad” command
Rx
20h
Read TA1, beginning offset = 20h
Rx
00h
Read TA2, address = 0020h
Rx
07h
Read E/S, ending offset = 111b, AA, PF = 0
Rx
Rx
Reset pulse
Presence pulse
Write 8 bytes of data to scratchpad
Read CRC to check for data integrity
Reset pulse
Presence pulse
Read scratchpad data and verify
Read CRC to check for data integrity
Tx
(Reset)
Rx
(Presence)
Reset pulse
Tx
CCh
Issue “Skip ROM” command
Tx
55h
Issue “Copy Scratchpad” command
Tx
20h
TA1
Tx
00h
TA2
Tx
07h
E/S
Presence pulse
(AUTHORIZATION CODE)
—
Rx
AAh
Tx
(Reset)
Rx
(Presence)
Tx
CCh
Issue “Skip ROM” command
Tx
F0h
Issue “Read Memory” command
Tx
00h
TA1, beginning offset = 00h
Tx
00h
TA2, address = 0000h
Rx
Tx
(Reset)
Rx
(Presence)
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Wait tPROGMAX for the copy function to complete
Read copy status, AAh = success
Reset pulse
Presence pulse
Read the entire memory
Reset pulse
Presence pulse
Maxim Integrated │ 22
DS2431
1024-Bit, 1-Wire EEPROM
Pin Configurations
SIDE VIEW
FRONT VIEW
GND
1
1
IO
2
2
N.C.
3
3
FRONT VIEW (T&R VERSION)
TO-92
1
2
3
TOP VIEW
TOP VIEW
TOP VIEW
+
1
IO
2
N.C.
3
6 N.C.
DS2431
GND
N.C.
N.C.
A1
A2
A3
DS2431
5 N.C.
4 N.C.
C1
IO
TSOC
C2
C3
N.C.
N.C.
N.C.
1
IO
2
GND
3
+
2431
ymrrF
GND
DS2431
*EP
UCSPR
*EXPOSED PAD
BOTTOM VIEW
1
DS2431G
6
N.C.
5
N.C.
4
N.C.
TDFN
(3mm x 3mm)
BOTTOM VIEW
2
GND
2
IO
1
DS2431GA
IO
GND
SFN
(6mm x 6mm x 0.9mm)
SFN
(3.5mm x 6.5mm x 0.75mm)
NOTE: THE SFN PACKAGE IS QUALIFIED FOR ELECTRO-MECHANICAL CONTACT APPLICATIONS ONLY, NOT FOR SOLDERING. FOR
MORE INFORMATION, REFER TO APPLICATION NOTE 4132: ATTACHMENT METHODS FOR THE ELECTRO-MECHANICAL SFN PACKAGE.
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Maxim Integrated │ 23
DS2431
1024-Bit, 1-Wire EEPROM
SFN Package Orientation on Tape and Reel
USER DIRECTION OF FEED
LEADS FACE UP IN ORIENTATION SHOWN ABOVE.
SFN
(6mm x 6mm x 0.9mm)
USER DIRECTION OF FEED
LEADS FACE UP IN ORIENTATION SHOWN ABOVE.
SFN
(3.5mm x 6.5mm x 0.75mm)
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Maxim Integrated │ 24
DS2431
1024-Bit, 1-Wire EEPROM
Package Information
For the latest package outline information and land patterns (footprints), go to www.maximintegrated.com/packages. Note that a “+”,
“#”, or “-” in the package code indicates RoHS status only. Package drawings may show a different suffix character, but the drawing
pertains to the package regardless of RoHS status.
PACKAGE TYPE
PACKAGE CODE
OUTLINE NO.
LAND PATTERN NO.
3 TO-92 (Bulk)
Q3+1
21-0248
—
3 TO-92 (T&R)
Q3+4
21-0250
—
6 TSOC
D6+1
21-0382
90-0321
2 SFN (6mm x 6mm)
G266N+1
21-0390
—
2 SFN (3.5mm x 6.5mm)
T23A6N+1
21-0575
—
6 TDFN-EP
T633+2
21-0137
90-0058
6 UCSPR
BR622+1
21-0376
Refer to
Application Note 1891
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Maxim Integrated │ 25
DS2431
1024-Bit, 1-Wire EEPROM
Revision History
REVISION
NUMBER
REVISION
DATE
0
050704
1
081604
PAGES
CHANGED
DESCRIPTION
Initial release
——
Replaced Pin Configuration
1
In the Electrical Characteristics table, changed VTL(MIN) from 0.5V to 0.46V and
VTL(MAX) from 4.1V to 4.4V; changed VHY(MIN) from 0.22V to 0.21V
2
In the Copy Scratchpad [55h] section, corrected the copy time from 13ms to 12.5ms
14
Added the SFN package and updated the Ordering Information table
1, 24
In the Pin Configuration, added a note to the CSP package outline “*See package
reliability report for important guidelines on qualified usage conditions.”
2
3
4
090506
122106
102207
1
In the Electrical Characteristics table, changed the tPROG (programming time) EC table
parameter from 12.5ms to 10ms for version A2 (see also pages 1, 13). Removed tFPD
and updated tPDH, tMSP, tW0L accordingly. Changed IPROG max to 0.8mA to match
GBD
1, 2, 3, 13
Updated Memory Function Example table
23
Added CSP package outline drawing number to Pin Configuration
1
Changed VTL(MIN) from 0.46V to 0.5V in the Electrical Characteristics table
2
In the Absolute Maximum Ratings, changed storage temp to -55°C to +125°C; in the
Electrical Characteristics table, changed VTH, VTL based on VPUP and data retention
to 40 years min at 85°C; added note to retention spec: “EEPROM writes can become
nonfunctional after the data-retention time is exceeded. Long-term storage at elevated
temperatures is not recommended; the device can lose its write capability after 10 years
at +125°C or 40 years at +85°C.”
1, 2, 3
In the Ordering Information table, removed all leaded part numbers and added the
TDFN-EP package
1, 24
In the Electrical Characteristics table, changed the VIL(MAX) spec from 0.3V to 0.5V;
removed e from the tW1L(MAX) spec; added Note 17 to tW0L spec; updated EC table
Notes 17 and 18; corrected Note 20
2, 3
Added EP function to the Pin Description table
3
Added e to Figure 11 Write-Zero Time Slot
19
In the Pin Configuration, added the package drawing information/weblink and a note that
the SFN package is qualified for electro-mechanical contact applications only, not for
soldering. Added the SFN Package Orientation on Tape-and-Reel section. In the Ordering
Information, added note to contact factory for availability of the UCSPR package. Added
note that TO-92 T&R leads are formed to approximately 100-mil spacing
24
In the SFN Pin Configuration, added reference to Application Note 4132
24
Added Package Information table
25
8/08
Created newer template-style data sheet
All
7
6/09
Deleted “contact factory” note in Ordering Information; updated Pin Description and Pin
Configurations to reflect changes in pin assignment of UCSPR package
8
10/09
Corrected part number in Ordering Information table
9
12/10
Deleted the automotive version reference in the Features section
1
10
3/11
Added the automotive version reference to the Features section
1
5
032008
6
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1, 5, 23
1
Maxim Integrated │ 26
DS2431
1024-Bit, 1-Wire EEPROM
Revision History (continued)
REVISION
NUMBER
REVISION
DATE
PAGES
CHANGED
11
1/12
Updated Note 1 in the Electrical Characteristics section; specified the data memory
default status and added a note that the memory must be programmed to FFh for the
EPROM mode to function to the Memory Access section
12
2/12
Added the 3.5mm x 6.5mm SFN package information to the Ordering Information table,
Pin Configurations, and Package Information table
13
3/12
Revised the Electrical Characteristics table Notes 4 and 15
3
14
11/14
Removed automotive references from Features section
1
15
3/15
Revised Benefits and Features section
1
DESCRIPTION
3, 7, 8
1, 23, 24, 25
For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642, or visit Maxim Integrated’s website at www.maximintegrated.com.
Maxim Integrated cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim Integrated product. No circuit patent licenses
are implied. Maxim Integrated reserves the right to change the circuitry and specifications without notice at any time. The parametric values (min and max limits)
shown in the Electrical Characteristics table are guaranteed. Other parametric values quoted in this data sheet are provided for guidance.
Maxim Integrated and the Maxim Integrated logo are trademarks of Maxim Integrated Products, Inc.
© 2015 Maxim Integrated Products, Inc. │ 27
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