Aaeon PCM-6890 User Manual page 121

;; Enter to I/O Chip Program Configuration Register Mode Enterv
Config proc
push
push
mov
mov
out
out
jmp
jmp
pop
pop
ret
EnterConfig endp
;; Exit to I/O Chip Program Configuration Register Mode
ExitConfig proc
push ax
push dx
mov
mov
out
pop
pop
ret
ax
dx
al,87h ;; Specific value to enter Config
;; Mode
dx,cs:CONFIG_PORT
dx,al ;; Write to Config Port twice!
dx,al
$+2 ;; Delay
$+2 ;;
dx
ax
al,0aah ;; Specific value to exit Config
;; Mode
dx,cs:CONFIG_PORT
dx,al
dx
ax
Appendix A Programming the Watchdog Timer 109