Rainbow Electronics LM87 - Manual (Page 19)

Functional Description
(Continued)
9.0 WATCHDOG LIMIT COMPARISONS AND
INTERRUPT STRUCTURE
Figure 10 depicts the Interrupt Structure of the LM87. The
LM87 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 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:
• 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 LM87 is expected to latch the event. The design of
the LM87 allows this input to go high even with no power
applied to the LM87, 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 LM87 to reset a typical
Chassis Intrusion circuit. This reset is activated by setting
Bit 7 of CI Clear Register (46h) high. The bit in the
Register is self-clearing.
10099531
FIGURE 10. Interrupt Structure
LM87
www.national.com 19