LM81CIMT-31 National Semiconductor, LM81CIMT-31 Datasheet - Page 18

• Manufacturer Part Number: LM81CIMT-31
• Description: Serial Interface ACPI-Compatible Microprocessor System
• Manufacturer: National Semiconductor

www.national.com
Functional Description
8.0 TEMPERATURE MEASUREMENT SYSTEM
The LM81 temperature sensor and ADC produce 9-bit or
12-bit two’s-complement temperature data. A digital com-
parator
user-programmable High, Low, Critical setpoints and Hyster-
esis values.
(Non-Linear Scale for Clarity)
(Non-Linear Scale for Clarity)
FIGURE 10. 12-bit Temperature-to-Digital Transfer
FIGURE 9. 9-bit Temperature-to-Digital Transfer
compares
the
Function
Function
temperature
(Continued)
data
DS100072-27
to
DS100072-24
the
18
8.1 Temperature Data Format
Temperature data can be read from the Temperature, T
setpoint, T
T
T
registers. T
temperature data is represented by an 8-bit, two’s comple-
ment word with an LSB (Least Significant Bit) equal to 1˚C:
By default Temperature Register data is represented by a
9-bit two’s complement digital word with the LSB having a
resolution of 0.5˚C:
In the extended mode temperature Register data can also be
represented by a 12-bit two’s complement digital word with
an LSB of 0.0625˚C:
T
with an LSB (Least Significant Bit) equal to 1˚C.
HYST
HIHYST
HYST
Temperature
Temperature
Temperature
+0.0625˚C
−0.0625˚C
+125˚C
+125˚C
+125˚C
+1.0˚C
−1.0˚C
+1.5˚C
−0.5˚C
+1.0˚C
−1.0˚C
+25˚C
−25˚C
−55˚C
+25˚C
−25˚C
−55˚C
+25˚C
−25˚C
−55˚C
Offset temperature data is represented by a 3-bit word
Offset registers; and written to the T
+0˚C
+0˚C
, T
0˚C
HIHYST
LOW
HIGH
setpoint, T_CRIT setpoint and T
setpoint, T
setpoint, T
0111 1100 0000
0001 1001 0000
0000 0001 0000
0000 0000 0001
0000 0000 0000
1111 1111 1111
1111 1111 0000
1110 0111 0000
1100 1001 0000
0 1111 1010
0 0011 0010
0 0000 0011
0 0000 0000
1 1111 1111
1 1100 1110
1 1001 0010
0111 1101
0001 1001
0000 0001
0000 0000
1111 1111
1110 0111
1100 1001
Binary
Binary
Binary
LOW
LOW
Digital Output
Digital Output
Digital Output
setpoint, T_CRIT setpoint
setpoint, T
C
HIGH
setpoint and
1 CEh
0 FAh
1 FFh
7 D0h
F FFh
F F0h
E 70h
C 90h
HYST
0 32h
0 03h
0 00h
1 92h
1 90h
0 10h
0 01h
0 00h
Hex
7Dh
C9h
Hex
Hex
19h
01h
00h
FFh
E7h
setpoint,
offset
HIGH