LM85 National Semiconductor, LM85 Datasheet - Page 14

• Manufacturer Part Number: LM85
• Description: Hardware Monitor with Integrated Fan Control
• Manufacturer: National Semiconductor

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Bit
6
7
Register
Address
42h
Bit
0
1
2
3
4
5
6
7
Functional Description
Register
Address
43h
4.9 Register 42h: Interrupt Status Register 2
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.
4.10 Register 43h: VID
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.
Name
Zone 3 Limit
Exceeded
Error in Status
Register 2
Name
+12V_Error
Reserved
Fan1 Stalled
Fan2 Stalled
Fan3 Stalled
Fan4 Stalled
Remote Diode
1 Fault
Remote Diode
2 Fault
Read/
Write
R
Read/
Write
R
Register
Name
Interrupt Status Register 2
CCP
Register
Name
VID0–4
Low Limit and V
R/W
R
R
R/W
R
R
R
R
R
R
R
R
Bit 7
(MSB)
RES
Default
0
0
Default
0
0
0
0
0
0
0
0
(Continued)
CCP
High Limit registers.
Bit 6
RES
Bit 7
(MSB)
ERR2
Description
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.
If there is a set bit in Status Register 2, this bit will be set to 1.
Description
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.
Reserved
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.
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.
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.
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.
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.
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.
Bit 6
ERR1
Bit 5
RES
14
Bit 5
FAN4
Bit 4
VID4
Bit 4
FAN3
Bit 3
VID3
Bit 3
FAN2
Bit 2
VID2
Bit 2
FAN1
Bit 1
VID1
Bit 1
RES
Bit 0
(LSB)
VID0
Bit 0
(LSB)
12V
Default
Value
Default
Value
00h