Datasheet

DS1921G
Step 4: Set the temperature alarms and write the Sample Rate to start the mission
In this example, the temperature alarms are set to -5°C for the low temperature threshold and 0°C for the high tem-
perature threshold. The sample rate is once every 10min, allowing the mission to last up to 14 days. This results in
the following data to be written to the special function registers:
With only a single DS1921G connected to the bus master, the communication of step 4 is as follows:
Thermochron iButton
40 ______________________________________________________________________________________
ADDRESS 20Bh 20Ch 20Dh
DATA 46h 50h 0Ah
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 0Bh TA1, beginning offset = 0Bh
Tx 02h TA2, address = 020Bh
Tx <3 data bytes> Write 3 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 0Bh Read TA1, beginning offset = 0Bh
Rx 02h Read TA2, address = 020Bh
Rx 0Dh Read E/S, ending offset = 0Dh, flags = 0h
Rx <3 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 0Bh TA1
Tx 02h TA2
Tx 0Dh E/S
(AUTHORIZATION CODE)
Tx (Reset) Reset pulse
Rx (Presence) Presence pulse
If step 4 is successful, the MIP bit in the Status register is 1, the MEMCLR bit is 0, and the Mission Start Delay
counts down.