LM81CIMT-3 National Semiconductor, LM81CIMT-3 Datasheet - Page 22

• Manufacturer Part Number: LM81CIMT-3
• Manufacturer: National Semiconductor

Specifications of LM81CIMT-3

• Monitored Voltage 1 (typ): 2.5/3.3/5/12V
• Battery Backup Switching: No
• Watchdog Timer: Yes
• Chip Enable Signals: No
• Manual Reset: No
• Package Type: TSSOP
• Operating Supply Voltage (min): 2.8V
• Operating Supply Voltage (max): 3.8V
• Operating Temp Range: -40C to 125C
• Operating Temperature Classification: Automotive
• Power Fail Detection: No
• Mounting: Surface Mount
• Pin Count: 24
• Lead Free Status / Rohs Status: Not Compliant

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Functional Description
9.0 THE LM81 INTERRUPT STRUCTURE
Figure 17 depicts the Interrupt Structure of the LM81. The
LM81 can generate Interrupts as a result of each of its
internal WATCHDOG registers on the analog, temperature,
and fan inputs.
External Interrupts can come from the following source.
While the label suggests a specific type or source of Inter-
rupt, this label is not a restriction of its usage, and it could
come from any desired source:
• Chassis Intrusion: This is an active high interrupt from
any type of device that detects and captures chassis
intrusion violations. This could be accomplished me-
chanically, optically, or electrically, and circuitry external
(Continued)
FIGURE 17. Interrupt Structure
22
All interrupts are indicated in the two Interrupt Status Regis-
ters. The INT output has two mask registers, and individual
to the LM81 is expected to latch the event. The design of
the LM81 allows this input to go high even with no power
applied to the LM81, and no clamping or other interfer-
ence with the line will occur. This line can also be pulled
low for at least 20 ms by the LM81 to reset a typical
Chassis Intrusion circuit. Accomplish this reset by setting
Bit 7 of CI Clear Register (45h) high. The bit in the
Register is self-clearing.
DS100072-22