DS2431G+U - Maxim Integrated

General Description

The DS2431 is a 1024-bit, 1-Wire® EEPROM chip orga-

nized 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 communi-

cates over the single-conductor 1-Wire bus. The com-

munication 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 Identication

●Medical Sensor Calibration Data Storage

●Analog Sensor Calibration Including IEEE P1451.4

Smart Sensors

● Ink and Toner Print Cartridge Identication

●After-Market Management of Consumables

Benets 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

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

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.

PART 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)

RPUP

VCC

µC

GND

DS2431

DS2431 1024-Bit, 1-Wire EEPROM

Typical Operating Circuit

Ordering Information

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

(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 ILIO 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

Standard speed, RPUP = 2.2kΩ 5

µs

Overdrive speed, RPUP = 2.2kΩ 2

Overdrive speed, directly prior to reset

pulse; RPUP = 2.2kΩ 5

Rising-Edge Hold-Off Time (Notes

5, 13) tREH

Standard speed 0.5 5.0 µs

Overdrive speed Not applicable (0)

Time Slot Duration

(Notes 2, 14) tSLOT

Standard speed 65 µs

Overdrive speed 8

IO PIN: 1-Wire RESET, PRESENCE-DETECT CYCLE

Reset Low Time (Note 2) tRSTL

Standard speed 480 640 µs

Overdrive speed 48 80

Presence-Detect High Time tPDH

Standard speed 15 60 µs

Overdrive speed 2 6

Presence-Detect Low Time tPDL

Standard speed 60 240 µs

Overdrive speed 8 24

Presence-Detect Sample Time

(Notes 2, 15) tMSP

Standard speed 60 75 µs

Overdrive speed 6 10

DS2431 1024-Bit, 1-Wire EEPROM

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Absolute Maximum Ratings

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)

Note 1: Limits are 100% production tested at TA = +25°C and/or TA = +85°C. Limits over the operating temperature range and rel-

evant 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 pres-

ence 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.

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

IO PIN: 1-Wire WRITE

Write-Zero Low Time

(Notes 2, 16, 17) tW0L

Standard speed 60 120

µsOverdrive speed, VPUP > 4.5V 5 15.5

Overdrive speed 6 15.5

Write-One Low Time

(Notes 2, 17) tW1L

Standard speed 1 15 µs

Overdrive speed 1 2

IO PIN: 1-Wire READ

Read Low Time

(Notes 2, 18) tRL

Standard speed 5 15 - d

µs

Overdrive speed 1 2 - d

Read Sample Time

(Notes 2, 18) tMSR

Standard speed tRL + d15 µs

Overdrive speed tRL + d2

EEPROM

Programming Current IPROG (Notes 5, 19) 0.8 mA

Programming Time tPROG (Notes 20, 21) 10 ms

Write/Erase Cycles (Endurance)

(Notes 22, 23) NCY

At +25°C 200k —

At +85°C (worst case) 50k

Data Retention

(Notes 24, 25, 26) tDR At +85°C (worst case) 40 Years

DS2431 1024-Bit, 1-Wire EEPROM

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Electrical Characteristics (continued)

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 tem-

peratures is not recommended; the device can lose its write capability after 10 years at +125°C or 40 years at +85°C.

*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.

PARAMETER

LEGACY VALUES DS2431 VALUES

STANDARD SPEED (µs) OVERDRIVE SPEED

(µs) STANDARD SPEED (µs) OVERDRIVE SPEED

(µs)

MIN MAX MIN MAX MIN MAX MIN MAX

tSLOT (including tREC) 61 (undened) 7(undened) 65* (undened) 8* (undened)

tRSTL 480 (undened) 48 80 480 640 48 80

tPDH 15 60 2 6 15 60 2 6

tPDL 60 240 8 24 60 240 8 24

tW0L 60 120 6 16 60 120 6 15.5

DS2431 1024-Bit, 1-Wire EEPROM

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Comparison Table

Detailed Description

The DS2431 combines 1024 bits of EEPROM, an 8-byte

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. Figure 1. Block Diagram

PIN NAME FUNCTION

TSOC TO-92 TDFN-EP SFN UCSPR

3, 4, 5, 6 3 1, 4, 5, 6 — A2, A3, C2,

C3 N.C. Not Connected

2 2 2 1 C1 IO 1-Wire Bus Interface. Open-drain signal

that requires an external pullup resistor.

1 1 3 2 A1 GND Ground Reference

— — — — — EP

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.

MEMORY

FUNCTION

CONTROL UNIT

DATA MEMORY

4 PAGES OF

256 BITS EACH

CRC-16

GENERATOR

64-BIT

SCRATCHPAD

1-Wire

FUNCTION CONTROL

64-BIT

LASERED ROM

PARASITE POWER

64 BITS

DS2431

DS2431 1024-Bit, 1-Wire EEPROM

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Pin Description

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 over-

drive 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 pro-

tocol for these memory function commands is described

in Figure 7. All data is read and written least signifi-

cant 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 polyno-

mial 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 reg-

ister contains the CRC value. Shifting in the 8 bits of the

CRC returns the shift register to all 0s.

Figure 2. Hierarchical Structure for 1-Wire Protocol

Figure 3. 64-Bit Lasered ROM

iButton is a registered trademark of Maxim Integrated Products, Inc.

DS2431 COMMAND LEVEL:

AVAILABLE COMMANDS: DATA FIELD AFFECTED:

READ ROM

MATCH ROM

SEARCH ROM

SKIP ROM

RESUME

OVERDRIVE-SKIP ROM

OVERDRIVE-MATCH ROM

64-BIT REG. #, RC-FLAG

RC-FLAG

RC-FLAG, OD-FLAG

64-BIT REG. #, RC-FLAG, OD-FLAG

1-Wire ROM FUNCTION COMMANDS

(SEE FIGURE 9)

WRITE SCRATCHPAD

READ SCRATCHPAD

COPY SCRATCHPAD

READ MEMORY

64-BIT SCRATCHPAD, FLAGS

64-BIT SCRATCHPAD

DATA MEMORY, REGISTER PAGE

DS2431-SPECIFIC

MEMORY FUNCTION COMMANDS

(SEE FIGURE 7)

MSB

8-BIT

CRC CODE 48-BIT SERIAL NUMBER

MSB MSBLSB

LSB

8-BIT FAMILY CODE

(2Dh)

MSBLSB

DS2431 1024-Bit, 1-Wire EEPROM

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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.

Figure 4. 1-Wire CRC Generator

Figure 5. Memory Map

1ST

STAGE

2ND

STAGE

3RD

STAGE

4TH

STAGE

7TH

STAGE

8TH

STAGE

6TH

STAGE

5TH

STAGE

X0X1X2X3X4

POLYNOMIAL = X8 + X5 + X4 + 1

INPUT DATA

X5X6X7X8

ADDRESS RANGE TYPE DESCRIPTION PROTECTION CODES

0000h to 001Fh R/(W) Data Memory Page 0 —

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.

DS2431 1024-Bit, 1-Wire EEPROM

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Contact the factory to set up and register a custom manu-

facturer ID. The last row is reserved for future use. It is

undefined in terms of R/W functionality and should not

be used.

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 bound-

ary, and 8 full bytes must be written into the scratchpad.

The protection control registers determine how incom-

ing 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 scratch-

pad. 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 associ-

ated 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.

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.

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 transfer-

status register used to verify data integrity with write com-

mands. 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 off-

set counter within the 8-byte scratchpad. Bit 5 of the E/S

is not valid due to a loss of power or if the master sends

fewer bytes than needed to reach the end of the scratch-

pad. 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 val-

ued 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.

Figure 6. Address Registers

BIT # 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

DS2431 1024-Bit, 1-Wire EEPROM

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Writing with Verication

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 func-

tion 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 scratch-

pad. 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

(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 com-

mand of 8 bytes starting at a valid row boundary. The

Write Scratchpad command accepts invalid addresses

and partial rows, but subsequent Copy Scratchpad com-

mands 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 writ-

ten 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 mas-

ter. 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 write-

protected 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.

DS2431 1024-Bit, 1-Wire EEPROM

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Figure 7a. Memory Function Flowchart

BUS MASTER Tx MEMORY

FUNCTION COMMAND

BUS MASTER Tx

TA1 (T[7:0]), TA2 (T[15:8])

BUS MASTER Rx

TA1 (T[7:0]), TA2 (T[15:8]),

AND E/S BYTE

BUS MASTER Rx

DATA BYTE FROM

SCRATCHPAD

MASTER Tx DATA BYTE

TO SCRATCHPAD APPLIES ONLY

IF THE MEMORY

AREA IS NOT

PROTECTED.

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.

BUS MASTER

Rx "1"s

DS2431

INCREMENTS

E[2:0]

PF = 0

DS2431

SETS PF = 1

CLEARS AA = 0

SETS E[2:0] = T[2:0]

0Fh

WRITE SCRATCHPAD? N

MASTER Tx RESET?

E[2:0] = 7?

T[2:0] = 0?

MASTER Tx RESET?

DS2431 SETS

SCRATCHPAD

BYTE COUNTER = T[2:0]

AAh

READ SCRATCHPAD? N

DS2431 Tx CRC-16 OF

COMMAND, ADDRESS,

AND DATA BYTES AS THEY

WERE SENT BY THE BUS

MASTER

BUS MASTER

Rx "1"s

NMASTER Tx RESET?

BUS MASTER Rx CRC-16

OF COMMAND, ADDRESS,

E/S BYTE, AND DATA BYTES

AS SENT BY THE DS2431

MASTER Tx RESET?

BYTE COUNTER

= E[2:0]?

FROM ROM FUNCTIONS

FLOWCHART (FIGURE 9)

TO ROM FUNCTIONS

FLOWCHART (FIGURE 9)

DS2431

INCREMENTS

BYTE COUNTER

TO FIGURE 7b

FROM FIGURE 7b

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Figure 7b. Memory Function Flowchart (continued)

BUS MASTER Tx

TA1 (T[7:0]), TA2 (T[15:8])

APPLICABLE TO ALL R/W

MEMORY LOCATIONS.

DURATION: tPROG *

* 1-Wire IDLE HIGH FOR POWER.

DS2431 COPIES

SCRATCHPAD

DATA TO ADDRESS

BUS MASTER

Rx "1"s

AA = 1

BUS MASTER

Rx "1"s

MASTER Tx RESET? NY

MASTER Tx RESET?

BUS MASTER Tx

TA1 (T[7:0]), TA2 (T[15:8])

AND E/S BYTE

55h

COPY SCRATCHPAD? N

DS2431 Tx "0"

DS2431 Tx "1"

F0h

READ MEMORY? N

AUTH. CODE

MATCH?

T[15:0] < 0090h?

PF = 0?

ADDRESS < 90h?

YCOPY PROTECTED?

BUS MASTER

Rx "1"s

MASTER Tx RESET?

DS2431 SETS MEMORY

ADDRESS = (T[15:0])

BUS MASTER Rx

DATA BYTE FROM

MEMORY ADDRESS

MASTER Tx RESET?

ADDRESS < 8Fh?

MASTER Tx RESET?

DS2431

INCREMENTS

ADDRESS

COUNTER

TO FIGURE 7a

FROM FIGURE 7a

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Read Scratchpad [AAh]

The Read Scratchpad command allows verifying the tar-

get 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 tar-

get 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.

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 microcon-

troller. 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 Conguration

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 three-

state 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 net-

work 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

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Initialization

All transactions on the 1-Wire bus begin with an initializa-

tion 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 pres-

ence 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 num-

ber, 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 pro-

duces 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 sub-

sequent 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.

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 registra-

tion 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 sys-

tem 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 com-

mand, data collision occurs on the bus as multiple slaves

transmit simultaneously (open-drain pulldowns produce a

wired-AND result).

Figure 8. Hardware Configuration

RPUP

VPUP

BUS MASTER

OPEN-DRAIN

PORT PIN 100 MOSFET

DATA

DS2431 1-Wire PORT

Rx = RECEIVE

Tx = TRANSMIT

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Figure 9a. ROM Functions Flowchart

DS2431 Tx

PRESENCE PULSE

BUS MASTER Tx

RESET PULSE

BUS MASTER Tx ROM

FUNCTION COMMAND

DS2431 Tx

CRC BYTE

DS2431 Tx

FAMILY CODE

(1 BYTE)

DS2431 Tx

SERIAL NUMBER

(6 BYTES)

RC = 0

MASTER Tx BIT 0

RC = 0 RC = 0 RC = 0

OD = 0

33h

READ ROM

COMMAND?

55h

MATCH ROM

COMMAND?

BIT 0 MATCH? BIT 0 MATCH?

N N

F0h

SEARCH ROM

COMMAND?

RESET PULSE?

CCh

SKIP ROM

COMMAND?

RC = 1

MASTER Tx BIT 1

MASTER Tx BIT 63

BIT 1 MATCH?

BIT 63 MATCH?

RC = 1

FROM MEMORY FUNCTIONS

FLOWCHART (FIGURE 7)

TO MEMORY FUNCTIONS

FLOWCHART (FIGURE 7)

DS2431 Tx BIT 0

MASTER Tx BIT 0

BIT 1 MATCH?

BIT 63 MATCH?

DS2431 Tx BIT 1

MASTER Tx BIT 1

DS2431 Tx BIT 63

MASTER Tx BIT 63

TO FIGURE 9b

FROM FIGURE 9b

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Figure 9b. ROM Functions Flowchart (continued)

RC = 0; OD = 1 RC = 0; OD = 1

BIT 0 MATCH?

RC = 1?

A5h

RESUME

COMMAND?

3Ch

OVERDRIVE-

SKIP ROM?

69h

OVERDRIVE-

MATCH ROM?

FROM FIGURE 9a

TO FIGURE 9a

MASTER Tx

RESET?

MASTER Tx

RESET?

NBIT 1 MATCH?

MASTER Tx BIT 0

MASTER Tx BIT 1

OD = 0

NOD = 0

RC = 1

BIT 63 MATCH?

MASTER Tx BIT 63

DS2431 1024-Bit, 1-Wire EEPROM

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Resume [A5h]

To maximize the data throughput in a multidrop environ-

ment, 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 pro-

cess. If more than one slave supporting overdrive is pres-

ent 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 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 multi-

drop 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 previ-

ous Overdrive-Skip ROM or successful Overdrive-Match

ROM 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 device or mul-

tiple devices on the bus.

1-Wire Signaling

The DS2431 requires strict protocols to ensure data integ-

rity. 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 dura-

tion 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 mem-

ory 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 commu-

nication. 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.

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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 defini-

tions 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 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 DS2431 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 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 t

+ δ (rise time) on one side and the internal

timing generator of the DS2431 on the other side define

the master sampling window (t

MSRMIN

to t

MSRMAX

), in

which the master must perform a read from the data line.

For the most reliable communication, t

should be as

short as permissible, and the master should read close

to but no later than t

MSRMAX

. After reading from the data

line, the master must wait until t

SLOT

is expired. This

guarantees sufficient recovery time t

REC

for the DS2431

to get ready for the next time slot. Note that t

REC

speci-

fied herein applies only to a single DS2431 attached to a

1-Wire line. For multidevice configurations, t

REC

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.

Figure 10. Initialization Procedure: Reset and Presence Pulse

RESISTOR MASTER DS2431

tRSTL tPDL

tRSTH

tPDH

MASTER Tx "RESET PULSE" MASTER Rx "PRESENCE PULSE"

VPUP

VIHMASTER

VTH

VTL

VILMAX

tREC

tMSP

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Figure 11. Read/Write Timing Diagrams

RESISTOR MASTER

RESISTOR MASTER DS2431

VPUP

VIHMASTER

VTH

VTL

VILMAX

VPUP

VIHMASTER

VTH

VTL

VILMAX

VPUP

VIHMASTER

VTH

VTL

VILMAX

tSLOT

tW1L

tREC

tSLOT

tW0L

tREC

MASTER

SAMPLING

WINDOW

tRL

tMSR

WRITE-ONE TIME SLOT

WRITE-ZERO TIME SLOT

READ-DATA TIME SLOT

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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-spe-

cific 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.

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.

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.

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

(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 speci-

fied 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.

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 com-

municated 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.

With the Write Scratchpad command, the CRC is gener-

ated by first clearing the CRC generator and then shifting

in the command code, the target addresses TA1 and TA2,

Figure 12. Noise Suppression Scheme

VPUP

VTH VHY

tREH

tGL

tREH

tGL

CASE A CASE CCASE B

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and all the data bytes as they were sent by the bus mas-

ter. The DS2431 transmits this CRC only if E[2:0] = 111b.

With the Read Scratchpad command, the CRC is gener-

ated 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.

Figure 13. CRC-16 Hardware Description and Polynomial

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.

<8–T[2:0] bytes> Transfer of as many bytes as needed to reach the end of the scratchpad for a given target address.

<Data to EOM> 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 Indenite loop where the master reads FF bytes.

AA Loop Indenite loop where the master reads AA bytes.

Programming Data transfer to EEPROM; no activity on the 1-Wire bus permitted during this time.

1ST

STAGE

2ND

STAGE

3RD

STAGE

4TH

STAGE

7TH

STAGE

8TH

STAGE

6TH

STAGE

5TH

STAGE

X0X1X2X3X4

POLYNOMIAL = X16 + X15 + X2 + 1

INPUT DATA

CRC OUTPUT

X5X6

11TH

STAGE

12TH

STAGE

15TH

STAGE

14TH

STAGE

13TH

STAGE

X11 X12

9TH

STAGE

10TH

STAGE

X9X10 X13 X14

16TH

STAGE

X16

X15

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Command-Specic 1-Wire Communication Protocol—Legend

Master to Slave Slave to Master Programming

Write Scratchpad (Cannot Fail)

RST PD Select WS TA <8–T[2:0] bytes> CRC-16 FF Loop

Read Scratchpad (Cannot Fail)

RST PD Select RS TA-E/S <8–T[2:0] bytes> 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 <Data to EOM> FF Loop

Read Memory (Invalid Address)

RST PD Select RM TA FF Loop

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Command-Specic 1-Wire Communication Protocol—Color Codes

1-Wire Communication Examples

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) COMMENTS

Tx (Reset) Reset pulse

Rx (Presence) Presence pulse

Tx CCh Issue “Skip ROM” command

Tx 0Fh Issue “Write Scratchpad” command

Tx 20h TA1, beginning offset = 20h

Tx 00h TA2, address = 0020h

Tx <8 Data Bytes> Write 8 bytes of data to scratchpad

Rx <2 Bytes CRC-16> Read CRC to check for data integrity

Tx (Reset) Reset pulse

Rx (Presence) Presence pulse

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 <8 Data Bytes> Read scratchpad data and verify

Rx <2 Bytes CRC-16> Read CRC to check for data integrity

Tx (Reset) Reset pulse

Rx (Presence) Presence pulse

Tx CCh Issue “Skip ROM” command

Tx 55h Issue “Copy Scratchpad” command

Tx 20h TA1

(AUTHORIZATION CODE)Tx 00h TA2

Tx 07h E/S

— <1-Wire Idle High> Wait tPROGMAX for the copy function to complete

Rx AAh Read copy status, AAh = success

Tx (Reset) Reset pulse

Rx (Presence) Presence pulse

Tx CCh Issue “Skip ROM” command

Tx F0h Issue “Read Memory” command

Tx 00h TA1, beginning offset = 00h

Tx 00h TA2, address = 0000h

Rx <144 Data Bytes> Read the entire memory

Tx (Reset) Reset pulse

Rx (Presence) Presence pulse

DS2431 1024-Bit, 1-Wire EEPROM

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│

N.C.

GND

TO-92

TOP VIEW

N.C.

GND

N.C.

TSOC

DS2431

SFN

(6mm x 6mm x 0.9mm)

SFN

(3.5mm x 6.5mm x 0.75mm)

BOTTOM VIEW BOTTOM VIEW

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

IO IO

GND

FRONT VIEW (T&R VERSION)

FRONT VIEWSIDE VIEW

DS2431

DS2431G

DS2431GA

UCSPR

TOP VIEW

GND N.C. N.C.

A1 A2 A3

C1 C2 C3

IO N.C. N.C.

1 6N.C. N.C.

2 5IO N.C.

3 4GND N.C.

TDFN

(3mm x 3mm)

TOP VIEW

DS2431

2431

ymrrF

*EP

*EXPOSED PAD

DS2431 1024-Bit, 1-Wire EEPROM

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│

Pin Congurations

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)

DS2431 1024-Bit, 1-Wire EEPROM

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│

SFN Package Orientation on Tape and Reel

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

DS2431 1024-Bit, 1-Wire EEPROM

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│

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.

REVISION

NUMBER

REVISION

DATE DESCRIPTION PAGES

CHANGED

0 050704 Initial release ——

1 081604

Replaced Pin Conguration 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

2 090506

Added the SFN package and updated the Ordering Information table 1, 24

In the Pin Conguration, added a note to the CSP package outline “*See package

reliability report for important guidelines on qualied usage conditions.” 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

3 122106

Added CSP package outline drawing number to Pin Conguration 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

4102207

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 Conguration, added the package drawing information/weblink and a note that

the SFN package is qualied 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

5 032008 In the SFN Pin Conguration, added reference to Application Note 4132 24

Added Package Information table 25

6 8/08 Created newer template-style data sheet All

7 6/09 Deleted “contact factory” note in Ordering Information; updated Pin Description and Pin

Congurations to reect changes in pin assignment of UCSPR package 1, 5, 23

8 10/09 Corrected part number in Ordering Information table 1

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

DS2431 1024-Bit, 1-Wire EEPROM

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│

Revision History

REVISION

NUMBER

REVISION

DATE DESCRIPTION PAGES

CHANGED

11 1/12

Updated Note 1 in the Electrical Characteristics section; specied 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

3, 7, 8

12 2/12 Added the 3.5mm x 6.5mm SFN package information to the Ordering Information table,

Pin Congurations, and Package Information table 1, 23, 24, 25

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 Benets and Features section 1

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 specications 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.

DS2431 1024-Bit, 1-Wire EEPROM

│

Revision History (continued)

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.