AAEON PFM-535S - Manual (Page 36)

P C / 1 0 4 C P U M o d u l e P F M - 5 3 5 S
Appendix A Programming the Watchdog Timer A-3
Here are steps to setup watchdog timer:
1. Set Bit 6 = 0 to disable the timer.
2. Write the desired counter value to 3Bh, 3Ah, 39h.
3. Set Bit 6 = 1 to enable the timer, the counter will begin to count
up.
4. When counter reaches the setting value, the time out will
generate signal setting by index 38h bit[7:4]
5. BIOS can read index 3Ch Bit 7 to decide whether the Watchdog
timeout event will happen or not.
To clear the watchdog timer counter:
1. Set Bit 6 = 0 to disable timer. This will also clear counter at the
same time.
WDT1
WDT1 does not use index and data port to access WDT registers. It
uses I/O port 68H~6DH. The time resolution of WDT1 is 30.5 u
second. Here are registers information: