Rainbow Electronics DS2404 - Manual (Page 12)

DS2404
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Example 2: Write two data bytes to memory locations 0026h and 0027h (the seventh and eighth byte of
page 1). Read entire memory (1-Wire port).
MASTER MODE DATA(LSB FIRST) COMMENTS
TX Reset reset pulse (480–960 ms)
RX Presence presence pulse
TX CCh Issue “skip ROM” command
TX 0Fh Issue “write scratchpad” command
TX 26h TA1, beginning offset=6
TX 00h TA2, address=0026h
TX <2 data bytes> Write 2 bytes of data to scratchpad
TX Reset reset pulse
RX Presence presence pulse
TX CCh Issue “skip ROM” command
TX AAh Issue “read scratchpad” command
RX 26h Read TA1, beginning offset=6
RX 00h Read TA2, address=0026h
RX 07h Read E/S, ending offset=7, flags=0
RX <2 data bytes> Read scratchpad data and verify
TX Reset reset pulse
RX Presence presence pulse
TX CCh Issue “skip ROM” command
TX 55h Issue “copy scratchpad” command
TX 26h
TX 00h
TX 07h
TA1
TA2
AUTHORIZATION CODE
E/S
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=0
TX 00h TA2, address=0000h
RX <542 bytes> Read entire memory
TX Reset reset pulse
RX Presence presence pulse, done
WRITE PROTECT/PROGRAMMABLE EXPIRATION
The write protect bits (WPR, WPI, WPC) provide a means of write protecting the timekeeping data and
limiting access to the DS2404 when an alarm occurs (programmable expiration).
The write protect bits may not be written by performing a single copy scratchpad command. Instead, to
write these bits, the copy scratchpad command must be performed three times. Please note that the AA bit
will be set, as expected, after the first copy command is successfully executed. Therefore, the
authorization pattern for the second and third copy command should have this bit set. The read
scratchpad command may be used to verify the authorization pattern.