Datasheet

Step 1: Set the RTC
Let the actual time be 15:30:00 hours on Monday, the 1st of April in 2002. This results in the following data to be writ-
ten to the RTC registers:
With only a single DS1921G connected to the bus master, the communication of step 1 is as follows:
DS1921G
Thermochron iButton
______________________________________________________________________________________ 37
ADDRESS 200h 201h 202h 203h 204h 205h 206h
DATA 00h 30h 15h 01h 81h 04h 02h
MASTER MODE DATA (LSB FIRST) COMMENTS
Tx (Reset) Reset pulse (480µs to 960µs)
Rx (Presence) Presence pulse
Tx CCh Issue Skip ROM command
Tx 0Fh Issue Write Scratchpad command
Tx 00h TA1, beginning offset = 00h
Tx 02h TA2, address = 0200h
Tx <7 data bytes> Write 7 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 00h Read TA1, beginning offset = 00h
Rx 02h Read TA2, address = 0200h
Rx 06h Read E/S, ending offset = 6h, flags = 0h
Rx <7 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 00h TA1
Tx 02h TA2
Tx 06h E/S
(AUTHORIZATION CODE)
Tx (Reset) Reset pulse
Rx (Presence) Presence pulse