Wdt0 – AAEON PFM-535S User Manual

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Appendix A Programming the Watchdog Timer A-2

A.1 Programming

There are two watchdog timers in Vortex86SX/DX CPU. One is

compatible with M6117D watchdog timer and the other is new. The

M6117D compatible watchdog timer is called WDT0 and new one is

called WDT1.

WDT0

To access WDT0 registers, programmer can use index port 22H

and data port 23H. The watchdog timer uses 32.768 kHz frequency

source to count a 24-bit counter so the time range is from 30.5u sec

to 512 sec with resolution 30.5u sec. When timer times out, a

system reset, NMI or IRQ may happen to be decided by BIOS

programming.