1024-Bit EEPROM iButton

22

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Memory Function Example

Write to the first 8 bytes of memory page 1. Read the

entire memory.

With only a single DS1972 connected to the bus mas-

ter, 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

Tx

00h

TA2

Tx

07h

E/S

(AUTHORIZATION CODE)

—

<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

PACKAGE TYPE

PACKAGE CODE

DOCUMENT NO.

F3 iButton

IB+3NT

21-0252

F5 iButton

IB+5NT

21-0266

Package Information

For the latest package outline information and land patterns, go to www.maxim-ic.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.