Acrosser AR-B1551 - Manual (Page 27)

AR-B1551 User’s Guide
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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
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 follow:
C:>debug
!
O 214 C8H
Generally, watchdog function would
reset system after 8 seconds
! O 214 0H
Disable watchdog function
C:>debug
!
O 214 88H
Generally, watchdog function would
generate IRQ 9 after 8 seconds
! O 214 0H
Disable watchdog function
3.3.2 Watchdog Timer Trigger
After you enable the watchdog timer, your program must write the same factor as enabling to the watchdog register
at least once every time-out period to its previous setting. You can change the time-out period by writing another
timer factor to the watchdog register at any time, and you must trigger the watchdog before the new time-out period
in next trigger.
4. INSTALLATION
This chapter describes the installation procedure. The following topics are covered:
! Overview
! Utility Diskettes