Rainbow-electronics DS2404 Manual do Utilizador descarregar pdf (Página 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.

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