Table of Contents
Advertisement
Programming the watchdog timer
How to program the WATCHDOG TIMER
1. Install WATCHDOG CLK Driver:
-- There is a file "DOG.EXE" in the supporting CD-ROM, please
run it before programming the WATCHDOG Timer. The driver
will initiate a 2 Hz frequency from CLK Generator for WATCH-
DOG Timer.
2. To set the time-out interval of watchdog timer:
-- output the desired value to port 0x443. Since the data is of 1
byte, the maximum value will be 255. In our design 2 ~ 255 will
denote 2 ~ 255 sec.
outportb(0x443, 30); // set watchdog to 30 seconds
3. To set the time-out event:
-- output data to prot 0x444,
• 0: reset system
• 1, 2, 3: IRQ 10, 15, 11 respectively
• 4: NMI
e.g.
outportb(0x444, 0); // set time-out event to reset-system
4. To disable watchdog timer:
-- output value 0 to port 0x443
outportb(0x443, 0); // disable watchdog timer
5. To ebable or refresh watchdog timer(the watchdog timer will
return to its initial value, then count down):
-- access the I/O port 0x443, e.g.
outportb(0x443, data); // refresh watchdog timer
* note: if you want to refresh the watchdog timer, you have to
disable it first.
108
SBC-557 User Manual
Advertisement
Table of Contents
