2.1 Internal Registers of the LM81

TABLE 1. The internal registers and their corresponding internal LM81 addresses are as follows:

Register

LM81 Internal Hex

Address

Power on

Value

Notes

Configuration Register

40h

0000 1000

Interrupt Status Register 1

41h

0000 0000

Interrupt Status Register 2

42h

0000 0000

Interrupt Mask Register 1

43h

0000 0000

Interrupt Mask Register 2

44h

0000 0000

CI Clear Register

46h

0000 0000

VID/Fan Divisor Register

47h

0101 XXXX

The upper four bits set the divisor for Fan Counters 1

and 2. The lower four bits reflect the state of the

VID0-VID3 inputs.

Serial Bus Address Register

48h

0010 11XX

The lower 2 bits reflect the state of A1 and A0, the

Serial Bus address input pins.

VID4 Register

49h

1000 000X

The lower bit reflects the state of VID4 input.

Temperature Configuration

Register

4Bh

0000 0001

Extended Mode Register 1

4Ch

0100 0100

Extended Mode Register 2

4Dh

0000 0000

Value RAM DAC Data

Register

19h

1111 1111

Value RAM

20h-3Fh

Contains: monitoring results (temperature, voltages,

fan counts), WATCHDOG limits, and

Company/Stepping IDs

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