LM80

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SNIS102F – JUNE 1999 – REVISED MARCH 2013

THE LM80 INTERRUPT STRUCTURE

Figure 12. Interrupt Structure

Figure 12 depicts the Interrupt Structure of the LM80. The LM80 can generate Interrupts as a result of each of its

internal WATCHDOG registers on the analog, temperature, and fan inputs.

Interrupt Inputs

External Interrupts can come from the following sources. While the label suggests a specific type or source of

Interrupt, this label is not a restriction of its usage, and it could come from any desired source:

•

BTI -

This is an active low Interrupt intended to come from the O.S. output of LM75 temperature sensors.

The LM75 O.S. output goes active when its temperature exceeds a programmed threshold. Up to 8 LM75's

can be connected to a single Serial Bus bus with their O.S. output's wire or'd to the BTI input of the LM80. If

the temperature of any LM75 exceeds its programmed limit, it drives BTI low. This generates an Interrupt to

notify the host of a possible overtemperature condition. Provides an internal pull-up of 10 k

Ω.

•

CI (Chassis Intrusion) -

This is an active high interrupt from any type of device that detects and captures

chassis intrusion violations. This could be accomplished mechanically, optically, or electrically, and circuitry

external to the LM80 is expected to latch the event. The design of the LM80 allows this input to go high even

with no power applied to the LM80, and no clamping or other interference with the line will occur. This line

can also be pulled low for at least 10 ms by the LM80 to reset a typical Chassis Intrusion circuit. Accomplish

this reset by setting Bit 5 of Configuration Register high. The bit in the Register is self-clearing.

•

INT_IN -

This active low Interrupt merely provides a way to chain the INT (Interrupt) from other devices

through the LM80 to the processor.

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