DS1820 datasheet(22/27 Pages) DALLAS

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DS1820

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MEMORY FUNCTION EXAMPLE Table 4

Example: Bus Master writes memory (parasite power and only one DS1820 assumed).

MASTER MODE

DATA (LSB FIRST)

COMMENTS

Reset

Reset pulse.

Presence

Presence pulse.

CCh

Skip ROM command.

4Eh

Write Scratchpad command.

<2 data bytes>

Writes two bytes to scratchpad (TH and TL).

Reset

Reset pulse.

Presence

Presence pulse.

CCh

Skip ROM command.

BEh

Read Scratchpad command.

<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 and the two other bytes

read back from the scratchpad. If data match, the master

continues; if not, repeat the sequence.

Reset

Reset pulse.

Presence

Presence pulse.

CCh

Skip ROM command.

48h

Copy Scratchpad command; after issuing this command,

the master must wait 6 ms for copy operation to complete.

Reset

Reset pulse.

Presence

Presence pulse, done.

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