3 watchdog timer, 1 watchdog timer setting – Acrosser AR-B1565 User Manual

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AR-B1565/1565A User’s Guide

3.3 WATCHDOG TIMER

This section describes the use of Watchdog Timer, including disable, enable, and trigger. AR-B1565/1565A is

equipped with a programmable time-out period watchdog timer that occupies I/O port 443H. Users can use simple

program to enable the watchdog timer. Once you enable the watchdog timer, the program should trigger it every

time before it times out. Watchdog Timer will generate a response (system or IRQ) due to system fails to trigger or

disable watchdog timer before preset timer, times out.

Watchdog

Time Base

Counter and

Compartor

RESET

Enable(D7)

Time Factor

(D0-D5)

Write and

Trigger

Watchdog Block Diagram

3.3.1 Watchdog Timer Setting

The watchdog timer is a circuit that maybe be used from your program software to detect crash or hang up. The

Watchdog timer is automatically disabled after reset. Once you enabled the watchdog timer, your program should

trigger the watchdog timer every time before it times out. After you trigger the watchdog timer, the timer will be set

to zero and start to count again. If your program fails to trigger the watchdog timer before times out, it will generate

a reset pulse to reset the system or trigger the IRQ 9 signal in order to tell your system that the watchdog time is

out.

Please refer to the following table in order to properly program Watchdog function

D5 D4 D3 D2 D1 D0

Enable Reset

Disable IRQ 9

Time period

Users could test watchdog function under ‘Debug’ program as follows:

C:>debug
! O 443 C8H

Generally, watchdog function would

reset system after 8 seconds

! O 443 0H
Disable watchdog function