DS1821SSLASHTR datasheet(14/18 Pages) DALLAS

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DS1821

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DS1821 OPERATION EXAMPLE

In this example, the master device programs the DS1821 with TL = +10°C and TH = +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

Reset

Master issues reset pulse.

Presence

DS1821 responds with presence pulse.

01h

Master issues Write TH command.

28h

Master sends data for TH = +40°C.

Reset

Master issues reset pulse.

Presence

DS1821 responds with presence pulse.

02h

Master issues Write TL command.

0Ah

Master sends data for TL = +10°C.

Reset

Master issues reset pulse.

Presence

DS1821 responds with presence pulse.

A1h

Master issues Read TH command.

28h

Master reads stored TH value to verify data.

Reset

Master issues reset pulse.

Presence

DS1821 responds with presence pulse.

A2h

Master issues Read TL command.

0Ah

Master reads stored TL value to verify data.

Reset

Master issues reset pulse.

Presence

DS1821 responds with presence pulse.

0Ch

Master issues Write Status command.

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.

DS1821S/TR Datasheet(PDF) 14 Page - Dallas Semiconductor

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