Datasheet

DS1825 Programmable Resolution 1-Wire Digital Thermometer With 4-Bit ID
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Figure 16. DETAILED MASTER READ 1 TIMING
Figure 17. RECOMMENDED MASTER READ 1 TIMING
DS1825 OPERATION EXAMPLE
In this example there are multiple DS1825s on the bus and they are using parasite power. The bus master initiates
a temperature conversion in a specific DS1825 and then reads its scratchpad and recalculates the CRC to verify
the data.
MASTER MODE DATA (LSB FIRST) COMMENTS
TX Reset Master issues reset pulse.
RX Presence DS1825s respond with presence pulse.
TX F0h
Master issues Search ROM command and builds
Crossreference Table
TX Reset Master issues reset pulse.
RX Presence DS1825s respond with presence pulse.
TX 55h Master issues Match ROM command for desired address
TX 64-bit ROM code Master sends DS1825 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 DS1825s respond with presence pulse.
TX 55h Master issues Match ROM command.
TX 64-bit ROM code Master sends DS1825 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 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.
V
PU
GND
1-WIRE BUS
15 ms
V
IH of Master
T
RC
T
INT
> 1 ms
Master samples
LINE TYPE LEGEND
Bus master pulling low
Resistor pullup
V
PU
GND
1-WIRE BUS
15 ms
V
IH of Master
T
RC
=
small
T
INT
=
small
Master samples