To enable the watchdog timer, you must write a program which writes I/O port address 443 (hex) at regular intervals. The output data is a timer value. You can write from 01 (hex) to 3C (hex), and the related timer is 1 sec. to 60 sec. After data entry, your program must refresh the watchdog timer by rewriting the I/O port 443 (hex) while simultaneously setting it. When you want to disable the watchdog timer, your program should read I/O port 043 (hex).Under linux this translates into manipulating the /dev/watchdog device. By opening the device and writing a value between 1 and 60 to it, the time-out value can be set. If this time-out is allowed to expire a RESET will be generated. Closing the device disables the watchdog.
This module also provides an interface to control the DSTN display/backlight. When the watchdog module is loaded and the /proc filesystem is enabled, a /proc/vga entry will become available. Reading this file will produce a '0' or '1' to indicated the current state of the DSTN display (off/on). By writing a 0/1 (off/on) to this file, the DSTN display can be turned on or off.
This driver was based on the drivers/char/acquirewdt.c source forming part of the 2.2.14-5 linux kernel shipped with the RedHat EDK.