LM85 National Semiconductor, LM85 Datasheet - Page 10

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

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Register
Address
6Fh
74h
75h
Register
Address
25h
26h
27h
Functional Description
Register
Address
20h
21h
22h
23h
24h
Note: Reserved bits will always return 0 when read.
4.1 Register 20-24h: Voltage Reading
The Register Names difine the typical input voltage at which the reading is
The Voltage Reading registers are updated automatically by the LM85 at a minimum frequency of 4 Hz. These registers are read
only — a write to these registers has no effect.
4.2 Register 25-27h: Temperature Reading
The Temperature Reading registers reflect the current temperatures of the internal and remote diodes. Processor (Zone1) Temp
register reports the temperature measured by the thermal diode connected to the Remote1− and Remote1+ pins, Remote
(Zone3) Temp register reports the temperature measured by the thermal diode connected to the the Remote2− and Remote2+
pins, and the Internal (Zone2) Temp register reports the temperature measured by the internal (junction) temperature sensor.
Temperatures are represented as 8 bit, 2’s complement, signed numbers, in Celsius, as shown below in Table 1. The Temperature
Reading register will return a value of 80h if the remote diode pins are not used by the board designer or are not functioning
properly. This reading will cause the zone limit bit(s) (bits 6 and 4) in the Interrupt Status Register (41h) and the remote diode fault
status bit(s) (bit 6 or 7) in the Interrupt Status Register 2 (42h) to be set. The Temperature Reading registers are updated
automatically by the LM85 at a minimum frequency of 4 Hz. These registers are read only — a write to these registers has no
effect.
Read/
Write
R/W
R/W
R/W
Read/
Write
R
R
R
Read/
Write
R
R
R
R
R
Register
Name
XOR Test Tree Enable
Tach Monitor Mode
Fan Spin-up Mode
Register
Name
Processor (Zone1) Temp
Internal (Zone2) Temp
Remote (Zone3) Temp
Register
Name
2.5V
V
3.3V
5V
12V
CCP
Temperature
Bit 7
(MSB)
7
7
7
7
7
TABLE 1. Temperature vs Register Reading
(Continued)
−127˚C
−50˚C
127˚C
0˚C
.
.
.
.
.
.
.
.
.
(MSB)
Bit 7
RES
RES
RES
Bit 6
6
6
6
6
6
Bit 7
(MSB)
7
7
7
Bit 6
RES
RES T3/4-1 T3/4-0
RES
Reading (Dec)
Bit 5
5
5
5
5
5
Bit 6
6
6
6
Bit 5
RES
RES
10
−127
−50
127
0
.
.
.
.
.
.
.
.
.
Bit 4
Bit 5
5
5
5
RES
RES
Bit 4
4
4
4
4
4
3
Bit 3
RES
T2-1
RES
⁄
Bit 4
4
4
4
4
Reading (Hex)
full scale or C0h.
Bit 3
3
3
3
3
3
CEh
81h
00h
7Fh
PWM3
Bit 2
Bit 3
3
3
3
RES
T2-0
.
.
.
.
.
.
.
.
.
SU
Bit 2
2
2
2
2
2
Bit 2
2
2
2
PWM2
Bit 1
RES
T1-1
SU
Bit 1
1
1
1
1
1
Bit 1
1
1
1
PWM1
(LSB)
Bit 0
XEN
T1-0
SU
Bit 0
(LSB)
0
0
0
0
0
Bit 0
(LSB)
0
0
0
Default
Value
00h
00h
7h
Default
Value
N/A
N/A
N/A
N/A
N/A
Default
Value
N/A
N/A
N/A
Lock?
U
U