DS1821
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DS1821 OPERATION EXAMPLE
In this example, the master device programs the DS1821 with T
L
= +10°C and T
H
= +40°C and verifies
that the data has been saved correctly. The master then programs the status/configuration register so that
the device will power-up in thermostat mode (T/R¯ = 1) and the thermostat output will have active high
polarity (POL = 1).
MASTER
MODE
DATA (LSB
FIRST)
COMMENTS
TX Reset Master issues reset pulse.
RX Presence DS1821 responds with presence pulse.
TX 01h Master issues Write TH command.
TX 28h Master sends data for T
H
= +40°C.
TX Reset Master issues reset pulse.
RX Presence DS1821 responds with presence pulse.
TX 02h Master issues Write TL command.
TX 0Ah Master sends data for T
L
= +10°C.
TX Reset Master issues reset pulse.
RX Presence DS1821 responds with presence pulse.
TX A1h Master issues Read TH command.
RX 28h Master reads stored T
H
value to verify data.
TX Reset Master issues reset pulse.
RX Presence DS1821 responds with presence pulse.
TX A2h Master issues Read TL command.
RX 0Ah Master reads stored T
L
value to verify data.
TX Reset Master issues reset pulse.
RX Presence DS1821 responds with presence pulse.
TX 0Ch Master issues Write Status command.
TX 06h
Master sends status/configuration data to the DS1821 with T/R¯ =
1 (thermostat mode at power-up) and POL = 1 (active high
thermostat output).
⎯ ⎯
Power is cycled; DS1821 powers-up in thermostat mode.
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