DS18S20-PAR Datasheet, PDF (17/20 Pages) Dallas Semiconductor – 1-Wire® Parasite-Power Digital Thermometer

DS18S20-PAR
DS18S20-PAR OPERATION EXAMPLE 2
In this example there are multiple DS18S20-PARs on the bus. The bus master initiates a temperature
conversion in a specific DS18S20-PAR and then reads its scratchpad and recalculates the CRC to verify
the data.
MASTER MODE
TX
RX
TX
TX
TX
TX
TX
RX
TX
TX
TX
RX
DATA (LSB FIRST)
Reset
Presence
55h
64-bit ROM code
44h
DQ line held high by
strong pullup
Reset
Presence
55h
64-bit ROM code
BEh
9 data bytes
COMMENTS
Master issues reset pulse.
DS18S20-PARs respond with presence pulse.
Master issues Match ROM command.
Master sends DS18S20-PAR ROM code.
Master issues Convert T command.
Master applies strong pullup to DQ for the duration of the
conversion (t_conv).
Master issues reset pulse.
DS18S20-PARs respond with presence pulse.
Master issues Match ROM command.
Master sends DS18S20-PAR ROM code.
Master issues Read Scratchpad command.
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.
DS18S20-PAR OPERATION EXAMPLE 3
In this example there is only one DS18S20-PAR on the bus. The bus master initiates a temperature
conversion then reads the DS18S20-PAR scratchpad and calculates a higher resolution result using the
data from the temperature, COUNT REMAIN and COUNT PER °C registers.
MASTER MODE
TX
TR
TX
TX
TX
TX
RX
TX
TX
RX
TX
RX
-
DATA (LSB FIRST)
Reset
Presence
CCh
44h
DQ line held high by
strong pullup
Reset
Presence
CCh
BEh
9 data bytes
Reset
Presence
-
COMMENTS
Master issues reset pulse.
DS18S20-PAR responds with presence pulse.
Master issues Skip ROM command.
Master issues Convert T command.
Master applies strong pullup to DQ for the duration of the
conversion (t_conv).
Master issues reset pulse.
DS18S20-PAR responds with presence pulse.
Master issues Skip ROM command.
Master issues Read Scratchpad command.
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. The master also calculates the
TEMP_READ value and stores the contents of the COUNT
REMAIN and COUNT PER °C registers.
Master issues reset pulse.
DS18S20-PAR responds with presence pulse.
CPU calculates extended resolution temperature using the
equation in the OPERATION - MEASURING
TEMPERATURE section of this datasheet.
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