DS75LX: Digital Thermometer and Thermostat with Extended Addressing

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Table 2. Configuration Register Bit Descriptions

BIT NAME

DESCRIPTION

0

Reserved

Power-Up State = 0

The master can write to this bit, but it always reads out as a 0.

R1

Conversion Resolution Bit 1

Power-Up State = 0

Sets conversion resolution (see Table 3).

R0

Conversion Resolution Bit 0

Power-Up State = 0

Sets conversion resolution (see Table 3).

F1

Thermostat Fault Tolerance Bit 1

Power-Up State = 0

Sets the thermostat fault tolerance (see Table 4).

F0

Thermostat Fault Tolerance Bit 0

Power-Up State = 0

Sets the thermostat fault tolerance (see Table 4).

POL

Thermostat Output (O.S.) Polarity

Power-Up State = 0

POL = 0 — O.S. is active low.

POL = 1 — O.S. is active high.

TM

Thermostat Operating Mode

Power-Up State = 0

TM = 0 — Comparator mode.

TM = 1 — Interrupt mode.

See the Operation—Thermostat section for a detailed description of

these modes.

SD

Shutdown

Power-Up State = 0

SD = 0 — Active conversion and thermostat operation.

SD = 1 — Shutdown mode.

See the Shutdown Mode section for a detailed description of this mode.

Table 3. Resolution Configuration

R1

R0

THERMOMETER

RESOLUTION (BITS)

MAX CONVERSION

TIME (ms)

0

0

9

25

0

1

10

50

1

0

11

100

1

1

12

200

Table 4. Fault Tolerance Configuration

F1

F0

CONSECUTIVE OUT-OF-LIMITS

CONVERSIONS TO TRIGGER O.S.

0

0

1

0

1

2

1

0

4

1

1

6

REGISTER POINTER

The four DS75LX registers each have a unique two-bit pointer designation, which is defined in Table 5. When

reading from or writing to the DS75LX, the user must “point” the DS75LX to the register that is to be accessed.

When reading from the DS75LX, once the pointer is set it remains pointed at the same register until it is changed.

For example, if the user wants to perform consecutive reads from the temperature register, the pointer only has to

be set to the temperature register one time, after which all reads will automatically be from the temperature register

until the pointer value is changed. On the other hand, when writing to the DS75LX, the pointer value must be

refreshed each time a write is performed, even if the same register is being written to twice in a row.

At power-up, the default pointer value is the temperature register so the temperature register can be read

immediately without resetting the pointer.

Changes to the pointer setting are accomplished as described in the 2-Wire Serial Data Bus.