Datasheet

Step 3: Set the search condition and Mission Start Delay and clear the alarm flags
In this example, the rollover is disabled and the search condition is set for a high temperature only. The mission is
to start with a delay of 90min (005Ah) and the alarm flags TLF, THF, and TAF are cleared. This results in the follow-
ing data to be written to the special function registers:
With only a single DS1921G connected to the bus master, the communication of step 3 is as follows:
DS1921G
Thermochron iButton
______________________________________________________________________________________ 39
ADDRESS 20Eh 20Fh 210h 211h 212h 213h 214h
DATA 02h 00h* 00h* 00h* 5Ah 00h 00h
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 0Eh TA1, beginning offset = 0Eh
Tx 02h TA2, address = 020Eh
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 0Eh Read TA1, beginning offset = 0Eh
Rx 02h Read TA2, address = 020Eh
Rx 14h Read E/S, ending offset = 14h, 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 0Eh TA1
Tx 02h TA2
Tx 13h E/S
(AUTHORIZATION CODE)
Tx (Reset) Reset pulse
Rx (Presence) Presence pulse
* Writing through address locations 20Fh to 211h is faster than accessing the Mission Start Delay register in a separate cycle. The
write attempt has no effect on the contents of these registers.