Rainbow-electronics DS1972 Manual do Utilizador descarregar pdf (Página 23)

DS1972: 1024-Bit EEPROM iButton

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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 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 CRC16\> 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 CRC16\> 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 (AUTHORIZATION CODE)

TX 07h E/S

<1-Wire idle high>

Wait t

PROGmax

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

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