Datasheet

DS18S20-PAR
16 of 20
DS18S20-PAR OPERATION EXAMPLE 1
In this example there is only one DS18S20-PAR on the bus. The master writes to the T
H
and T
L
registers
in the DS18S20-PAR scratchpad and then reads the scratchpad and recalculates the CRC to verify the
data. The master then copies the scratchpad contents to EEPROM.
MASTER MODE DATA (LSB FIRST) COMMENTS
TX Reset Master issues reset pulse.
RX Presence DS18S20-PAR responds with presence pulse.
TX CCh Master issues Skip ROM command.
TX 4Eh Master issues Write Scratchpad command.
TX 2 data bytes Master sends two data bytes to scratchpad (T
H
and T
L
).
TX Reset Master issues reset pulse.
RX Presence DS18S20-PAR responds with presence pulse.
TX CCh Master issues Skip ROM command.
TX BEh Master issues Read Scratchpad command.
RX 9 data bytes Master reads entire scratchpad including CRC. The master then
recalculates the CRC of the first eight data bytes from the
scratchpad and compares the calculated CRC with the read CRC
(byte 9). If they match, the master continues; if not, the read
operation is repeated.
TX Reset Master issues reset pulse.
RX Presence DS18S20-PAR responds with presence pulse.
TX CCh Master issues Skip ROM command.
TX 48h Master issues Copy Scratchpad command.
TX DQ line held high by
strong pullup
Master applies strong pullup to DQ for at least 10 ms while copy
operation is in progress.