DS1820

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MEMORY FUNCTION EXAMPLE Table 3

Example: Bus Master initiates temperature conversion, then reads temperature (parasite power assumed).

MASTER MODE

DATA (LSB FIRST)

COMMENTS

TX

Reset

Reset pulse (480–960

µs).

RX

Presence

Presence pulse.

TX

55h

Issue “Match ROM” command.

TX

<64–bit ROM code>

Issue address for DS1820.

TX

44h

Issue “Convert T” command.

TX

<I/O LINE HIGH>

I/O line is held high for at least 500 ms 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 DS1820.

TX

BEh

Issue “Read Scratchpad” command.

RX

<9 data bytes>

Read entire scratchpad plus CRC; the master now recal-

culates 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.