Aaeon PCM-5892, Manual

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102 PCM-5894/5892 User Manual
Programming the watchdog timer
How to program the WATCHDOG TIMER
1. To set the time-out interval of watchdog timer:
-- output the desired value to port 0x443. Since the data is of 1
byte, the maximum value will be 255. In our design 1 ~ 127 will
denote 1sec ~ 127sec, though 129 ~ 255 will denote lmin ~
127min. e.g.
outportb(0x443, 30); // set interval to 30 seconds
outportb(0x443, 0x85); // set interval to 5 minutes
2. To set the time-out event:
-- output data to prot 0x444,
• 0: reset system
• 1, 2, 3: IRQ 10, 15, 11 respectively
• 4: NMI
e.g.
outportb(0x444, 0); // set time-out event to reset-system
3. To disable watchdog timer:
-- output any value to port 0x80, e.g.
outportb(0x80, data); // disable watchdog timer
4. To ebable or refresh watchdog timer(the watchdog timer will
return to its initial value, then count down):
-- access the I/O port 0x443, e.g.
outportb(0x80, 0); // disable watchdog timer
inportb(0x443); // refresh watchdog timer
* note: if you want to refresh the watchdog timer, you have to
disable it first.