Bit

Name

R/W

Default

Description

6

Zone 3 Limit

Exceeded

R

0

The LM85 automatically sets this bit to 1 when the temperature input

measured by the Remote2− and Remote2+ inputs is less than or equal to

the limit set in the Internal (Zone2) Low Temp register or greater than the

limit set in the Remote (Zone3) High Temp register. This bit will be set

when a diode fault is detected.

7

Error in Status

Register 2

R

0

If there is a set bit in Status Register 2, this bit will be set to 1.

4.9 Register 42h: Interrupt Status Register 2

Register

Address

Read/

Write

Register

Name

Bit 7

(MSB)

Bit 6

Bit 5

Bit 4

Bit 3

Bit 2

Bit 1

Bit 0

(LSB)

Default

Value

42h

R

Interrupt Status Register 2

ERR2

ERR1

FAN4

FAN3

FAN2

FAN1

RES

12V

00h

The Interrupt Status Register 2 bits will be automatically set, by the LM85, whenever a fault condition is detected. Interrupt Status

Register 2 identifies faults caused by temperature sensor error, fan speed droping below minimum set by the tachometer

minimum register, the 12V input voltage going outside the window set by its limit registers. Interrupt Status Register 2 will hold

a set bit until the event is read by software. The contents of this register will be cleared (set to 0) automatically by the LM85 after

it is ready by software, if fault condition no longer exists. Once set, the Interrupt Status Register 2 bits will remain set until a read

event occurs, even if the fault no longer exists

This register is read only — a write to this register has no effect.

Bit

Name

R/W

Default

Description

0

+12V_Error

R

0

The LM85 automatically sets this bit to 1 when the 12V input voltage either

falls below the limit set in the 12V Low Limit register or exceeds the limit

set in the 12V High Limit register.

1

Reserved

R

0

Reserved

2

Fan1 Stalled

R

0

The LM85 automatically sets this bit to 1 when the TACH1 input reading is

above the value set in the Tach1 Minimum MSB and LSB registers.

3

Fan2 Stalled

R

0

The LM85 automatically sets this bit to 1 when the TACH2 input reading is

above the value set in the Tach2 Minimum MSB and LSB registers.

4

Fan3 Stalled

R

0

The LM85 automatically sets this bit to 1 when the TACH3 input reading is

above the value set in the Tach3 Minimum MSB and LSB registers.

5

Fan4 Stalled

R

0

The LM85 automatically sets this bit to 1 when the TACH4 input reading is

above the value set in the Tach4 Minimum MSB and LSB registers.

6

Remote Diode

1 Fault

R

0

The LM85 automatically sets this bit to 1 when there is either a short or

open circuit fault on the Remote1+ or Remote1− thermal diode input pins.

A diode fault will also set bit 4, Diode 1 Zone Limit bit, of Interrupt Status

Register 1.

7

Remote Diode

2 Fault

R

0

The LM85 automatically sets this bit to 1 when there is either a short or

open circuit fault on the Remote2+ or Remote2− thermal diode input pins.

A diode fault will also set bit 6, Diode 2 Zone Limit bit, of Interrupt Status

Register 1.

4.10 Register 43h: VID

Register

Address

Read/

Write

Register

Name

Bit 7

(MSB)

Bit 6

Bit 5

Bit 4

Bit 3

Bit 2

Bit 1

Bit 0

(LSB)

Default

Value

43h

R

VID0–4

RES

RES

RES

VID4

VID3

VID2

VID1

VID0

The VID register contains the values of LM85 VID0–VID4 input pins. This register indicates the status of the VID lines that

interconnect the processor to the Voltage Regulator Module (VRM). Software uses the information in this register to determine the

voltage that the processor is designed to operate at. With this information, software can then dynamically determine the correct

values to place in the V

This register is read only — a write to this register has no effect.

www.national.com

14