Acrosser AR-B1565 - Manual (Page 31)

AR-B1565/1565A User’s Guide
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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
Register
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
D7 D6 D5 D4 D3 D2 D1 D0
1 Enable Reset
0 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