IBM All-in-One FC/Socket 370 Celeron, PCM-6890B manual Appendix a Programming the Watchdog Timer

W977Write PROC
push	dx
call	EnterConfig	;; Enter Config Mode
call	SelectDevice	;; Select logical device
mov	dx,cs:CONFIG_PORT
out	dx,al	;; Select register number
mov	al,ah
mov	dx,cs:DATA_PORT
out	dx,al
call	ExitConfig	;; Exit Config Mode
pop	dx
ret
W977Write ENDP
end

Appendix A Programming the Watchdog Timer 107