1 register 20-24h: voltage reading, 2 register 25-27h: temperature reading, Table 1. temperature vs register reading – Rainbow Electronics LM85 User Manual
Page 10: Functional description
Functional Description
(Continued)
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
Lock?
6Fh
R/W
XOR Test Tree Enable
RES
RES
RES
RES
RES
RES
RES
XEN
00h
U
74h
R/W
Tach Monitor Mode
RES
RES T3/4-1 T3/4-0
T2-1
T2-0
T1-1
T1-0
00h
75h
R/W
Fan Spin-up Mode
RES
RES
RES
RES
RES
PWM3
SU
PWM2
SU
PWM1
SU
7h
U
Note: Reserved bits will always return 0 when read.
4.1 Register 20-24h: Voltage Reading
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
20h
R
2.5V
7
6
5
4
3
2
1
0
N/A
21h
R
V
CCP
7
6
5
4
3
2
1
0
N/A
22h
R
3.3V
7
6
5
4
3
2
1
0
N/A
23h
R
5V
7
6
5
4
3
2
1
0
N/A
24h
R
12V
7
6
5
4
3
2
1
0
N/A
The Register Names difine the typical input voltage at which the reading is
3
⁄
4
full scale or C0h.
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
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
25h
R
Processor (Zone1) Temp
7
6
5
4
3
2
1
0
N/A
26h
R
Internal (Zone2) Temp
7
6
5
4
3
2
1
0
N/A
27h
R
Remote (Zone3) Temp
7
6
5
4
3
2
1
0
N/A
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.
TABLE 1. Temperature vs Register Reading
Temperature
Reading (Dec)
Reading (Hex)
−127˚C
−127
81h
.
.
.
.
.
.
.
.
.
−50˚C
−50
CEh
.
.
.
.
.
.
.
.
.
0˚C
0
00h
.
.
.
.
.
.
.
.
.
127˚C
127
7Fh
LM85
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