DS1921G Maxim, DS1921G Datasheet - Page 40

• Manufacturer Part Number: DS1921G
• Description: The DS1921G Thermochron® iButton® is a rugged, self-sufficient system that measures temperature and records the result in a protected memory section
• Manufacturer: Maxim

Thermochron iButton
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:
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.
40
MASTER MODE
______________________________________________________________________________________
ADDRESS
Rx
Rx
Rx
Rx
Rx
Rx
Rx
Rx
Tx
Tx
Tx
Tx
Tx
Tx
Tx
Tx
Tx
Tx
Tx
Tx
Tx
Tx
Tx
Tx
DATA
DATA (LSB FIRST)
<3 data bytes>
<3 data bytes>
(Presence)
(Presence)
(Presence)
(Presence)
(Reset)
(Reset)
(Reset)
(Reset)
CCh
CCh
CCh
AAh
0Bh
0Bh
0Dh
0Bh
0Dh
0Fh
02h
02h
55h
02h
20Bh
46h
Reset pulse (480μs to 960μs)
Presence pulse
Issue Skip ROM command
Issue Write Scratchpad command
TA1, beginning offset = 0Bh
TA2, address = 020Bh
Write 3 bytes of data to scratchpad
Reset pulse
Presence pulse
Issue Skip ROM command
Issue Read Scratchpad command
Read TA1, beginning offset = 0Bh
Read TA2, address = 020Bh
Read E/S, ending offset = 0Dh, flags = 0h
Read scratchpad data and verify
Reset pulse
Presence pulse
Issue Skip ROM command
Issue Copy Scratchpad command
TA1
TA2
E/S
Reset pulse
Presence pulse
(AUTHORIZATION CODE)
20Ch
50h
COMMENTS
20Dh
0Ah