B&B Electronics PC Watchdog Timer Card ATRWDT Bedienungsanleitung PDF herunterladen (Seite 6)

P104-WDG-CSM User Manual

The Watchdog card can generate an interrupt request one Counter 0 period-width before the

reset timeout. For example, if a reset period of 60 seconds is used with a 5 millisecond delay

stored in Counter 0 (the result of a maximum value delay), an interrupt would occur at 59.995

seconds. This gives the Interrupt handler software 5 milliseconds to refresh the watchdog

before a reset action occurs. This should allow your software to take corrective actions if the

system software continued to run but the software that should have reset the watchdog had

failed. Discussion of these Watchdog Programming Options is given in a later chapter.

Figure 1-1: Block Diagram

Watchdog Models

There are three basic models of this board. Special variations can be configured by contacting

the sales department. (See Chapter 5 for pinout.)

P104-WDG-E: Economy Basic Watchdog

This model provides a fully programmable watchdog with open collector outputs that

can reset the computer. Both “WDRST” and “not WDRST” outputs are provided on the

four pin header connector:

a. Open collector watchdog output, active HIGH, 1k pull-up to 5V.

b. Open collector watchdog output, active LOW, no current limiting.

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B&B Electronics PC Watchdog Timer Card ATRWDT Bedienungsanleitung Seite 6