Rainbow Electronics DS1972 - Manual (Page 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
¾ <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