Acrosser AR-B1551 User Manual

Page 26

AR-B1551 User s Guide

3.3 WATCHDOG TIMER

This section describes how to use the Watchdog Timer disabled, enabled, and trigger. The AR-B1570 is equipped
with a programmable time-out period watchdog timer that occupies I/O post 214H. User can use the program to
enable the watchdog timer. Once you enable the watchdog timer, the program should trigger it every time before it
times out. And because of the system hang up, your program fails to trigger and disable the timer before it times
out. It will generate a reset signal to reset the system. The time-out period can be programmed to be 0 to 63
seconds.

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, it will be set to zero
and start to count again. If your program fails to trigger the watchdog timer before time 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

1 Enable Reset

0 Disable IRQ 9

Time period