Axiomtek MANO861 - Manual (Page 69)

MANO861 Mini ITX Board
Watchdog Timer 61
Appendix A
Watchdog Timer
About Watchdog Timer
Software stability is major issue in most application. Some embedded systems are not
watched by human for 24 hours. It is usually too slow to wait for someone to reboot when
computer hangs. The systems need to be able to reset automatically when things go wrong.
The watchdog timer gives us solution.
The watchdog timer is a counter that triggers a system reset when it counts down to zero from
a preset value. The software starts counter with an initial value and must reset it periodically. If
the counter ever reaches zero which means the software has crashed, the system will reboot.
The integrated watchdog timer can be set up by programming. There are 1~255 levels
available.
How to Use Watchdog Timer
Assume that program A needs to keep running in a system. The value of watchdog timer must
be set bigger than the running time of program A. Then, after the running time of program A is
finished, either to disable or to reset watchdog timer.
When program A has problems that cause system shut down, the system can be rebooted by
watchdog timer when the value of watchdog timer has counted down to 0.
Begin
Enable and Initialize
Watchdog Timer
Program “A”
Disable Watchdog
Timer
Next
Next
Next
Next
Begin
Enable and Initialize
Watchdog Timer
Program “A”
Reset Watchdog
Timer
Next
Next
Next
Next