LM78 National Semiconductor, LM78 Datasheet - Page 21

• Manufacturer Part Number: LM78
• Description: Microprocessor System Hardware Monitor
• Manufacturer: National Semiconductor

Functional Description
8.0 THE LM78 INTERRUPT STRUCTURE
Figure 12 depicts the Interrupt Structure of the LM78. The
LM78 can generate Interrupts as a result of each of its
internal WATCHDOG registers on the analog, temperature,
and fan inputs. Overflow of the POST RAM (greater than 32
bytes written to POST RAM) will also cause an Interrupt.
External Interrupts can come from the following three
sources. While the labels suggest a specific type or source
of Interrupt, these labels are not restrictions of their usage,
and they could come from any desired source:
• BTI:
from the O.S. output of LM75 temperature sensors. The
LM75 O.S. output goes active when its temperature ex-
This is an active low Interrupt intended to come
(Continued)
FIGURE 12. Interrupt Structure
21
ceeds 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 LM78. 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 .
DS012873-21
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