DS1921H/Z
STEP 4
In this example, the temperature alarms are set to 0°C for the low temperature threshold and 10°C for the
high temperature threshold, assuming it is a DS1921Z device. The sample rate is once every 10 minutes,
allowing the mission to last up to 14 days. This results in the following data to be written to the special
function registers:
Address:
Data:
20Bh
2Ch
20Ch
7Ch
20Dh
0Ah
With only a single DS1921H/Z connected to the bus master, the communication of step 4 is as follows:
MASTER MODE
DATA (LSB FIRST)
(Reset)
(Presence)
CCh
COMMENTS
TX
RX
TX
TX
TX
TX
TX
TX
RX
TX
TX
RX
RX
RX
RX
TX
RX
TX
TX
TX
TX
TX
TX
RX
Reset pulse (480µs to 960µs)
Presence pulse
Issue Skip ROM command
Issue Write Scratchpad command
TA1, beginning offset = 0Bh
TA2, address = 020Bh
0Fh
0Bh
02h
<3 data bytes>
(Reset)
(Presence)
CCh
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
AAh
0Bh
02h
0Dh
<3 data bytes>
(Reset)
(Presence)
CCh
Presence pulse
Issue Skip ROM command
Issue Copy Scratchpad command
TA1
55h
0Bh
TA2
E/S
(AUTHORIZATION CODE)
02h
0Dh
(Reset)
(Presence)
Reset pulse
Presence pulse
If step 4 was successful, the MIP bit in the Status Register will be 1, the MEMCLR bit will be 0, and the
mission start delay will be counting down.
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DALLAS [ DALLAS SEMICONDUCTOR ]
