LM80 datasheet(19/29 Pages) NSC

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Functional Description (Continued)

8.0 THE LM80 INTERRUPT STRUCTURE

Figure 10 depicts the Interrupt Structure of the LM80. The

LM80 can generate Interrupts as a result of each of its inter-

nal WATCHDOG registers on the analog, temperature, and

fan inputs.

8.1 INTERRUPT INPUTS

External Interrupts can come from the following sources.

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:

•

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 ex-

ceeds a programmed threshold. Up to 8 LM75’s can be

connected to a single Serial Bus bus with their O.S. out-

put’s wire or’d to the BTI input of the LM80. If the tem-

perature 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 me-

chanically, 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 interfer-

ence 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 Regis-

ter is self-clearing.

DS100040-18

FIGURE 10. Interrupt Structure

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