Aaeon SBC-357, Руководство пользователя, Страница: 70 / 78

62 SBC-357 User Manual
Watchdog timer
The watchdog timer uses 32.768 MHz frequency source to
counter a 24-bit Counter, so the timer 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 user’s
programming.
Configuration register
The watchdog timer of SBC-357 is located on the chipset - ALI
M6117C. If you want to use it, you have to know how to read/
write the configuration register of M6117C. Following is the
basic procedure.
1. Open the chip.
2. Write/Read data to/from register.
3. Close the chip.
To Open/Close the chip is to write a specific value to register
13h.
Index 13h:
c5h: open the chip
ooh: close the chip
Here we give you an example of writing data to register.
mov al, 13h
Out 22h, al
jmp $+2 ;;delay
jmp $+2 ;;delay
mov al, oc5h
out 23h, al
* note: 22h is the index I/O port, 23h is the data I/O port.
How to set the watchdog timer