Datasheet

DS1920
18 of 22
MEMORY FUNCTION EXAMPLE Table 3
Example: Bus Master initiates temperature conversion, then reads temperature.
MASTER MODE
DATA (LSB FIRST)
COMMENTS
Tx
Reset
Reset pulse(480–960µs)
Rx
Presence
Presence pulse
Tx
55h
Issue “Match ROM” command
Tx
<64-bit ROM code>
Issue address for DS1920
Tx
44h
Issue “Convert Temperature” command
Tx <DATA LINE HIGH>
Data line is held high for at least 0.75 seconds by bus
master to allow conversion to complete.
Tx
Reset
Reset pulse
Rx
Presence
Presence pulse
Tx
55h
Issue “Match ROM” command
Tx
<64-bit ROM code>
Issue address for DS1920
Tx
BEh
Issue “Read Scratchpad” command.
Rx <9 data bytes>
Read entire scratchpad plus CRC; the master now
recalculates the CRC of the eight data bytes received
from the scratchpad, compares the CRC calculated and
the CRC read. If they match, the master continues; if
not, this read operation is repeated.
Tx
Reset
Reset pulse
Rx
Presence
Presence pulse, done