Functional Description (Continued)
Address A6–A0
Description
2Ah
2Bh
2Ch
2Dh
2Eh
2Fh
30h
31h
32h
33h
34h
35h
36h
37h
38h
39h
3Ah
3Bh
Reserved
+2.5V High Limit/External Temperature 2 High Limit
+2.5V Low Limit/External Temperature 2 Low Limit
Vccp1 High Limit
Vccp1 Low Limit
+3.3V High Limit
+3.3V Low Limit
+5V High Limit
+5V Low Limit
+12V High Limit
+12V Low Limit
Vccp2 High Limit
Vccp2 Low Limit
External Temperature 1 High Limit
External Temperature 1 Low Limit
Internal Temperature High Limit
Internal Temperature Low Limit
FAN1Count Limit/AIN1 High Limit
Note: It is the number of counts of the internal clock for the Low Limit of the fan speed.
FAN2 Fan Count Limit/AIN2 High Limit
3Ch
Note: It is the number of counts of the internal clock for the Low Limit of the fan speed.
Reserved
3Dh
3Eh
Company Identification. The number in this register identifies National Semiconductor LM87 (0000
0010)
3Fh
Stepping Register LM87 revision number 06h(0000 0110)
Note: Setting all ones to the high limits for voltages and fans (0111 1111
binary for temperature) means interrupts will never be generated
except the case when voltages go below the low limits.
For voltage input high limits, the device is doing a greater than com-
parison. For low limits, however, it is doing a less than or equal to
comparison.
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