Datasheet

Ds18S20 Operation Example 1
In this example there are multiple DS18S20s on the bus and they are using parasite power. The bus master initiates a
temperature conversion in a specific DS18S20 and then reads its scratchpad and recalculates the CRC to verify the data.
DS18S20 Operation Example 2
In this example there is only one DS18S20 on the bus and it is using parasite power. The master writes to the T
H
and
T
L
registers in the DS18S20 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 DS18S20s respond with presence pulse.
Tx 55h Master issues Match ROM command.
Tx 64-bit ROM code Master sends DS18S20 ROM code.
Tx 44h Master issues Convert T command.
Tx
DQ line held high by
strong pullup
Master applies strong pullup to DQ for the duration of the
conversion (t
CONV
).
Tx Reset Master issues reset pulse.
Rx Presence DS18S20s respond with presence pulse.
Tx 55h Master issues Match ROM command.
Tx 64-bit ROM code Master sends DS18S20 ROM code.
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 rst 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.
MASTER MODE DATA (LSB FIRST) COMMENTS
Tx Reset Master issues reset pulse.
Rx Presence DS18S20 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 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 rst 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 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 10ms while copy
operation is in progress.
DS18S20 High-Precision 1-Wire Digital Thermometer
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