Ibm All-in-One Super7 Single Board Computer PCM-5896 Manuale Utente Scaricare il pdf (Pagina 118)

106 PCM-5896 User Manual

Programming the watchdog timer

How to program the WATCHDOG TIMER

1. 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

2. 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

3. To disable watchdog timer:

-- output value 0 to port 0x443

outportb(0x443, 0); // disable watchdog timer

4. 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.

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Ibm All-in-One Super7 Single Board Computer PCM-5896 Manuale Utente Pagina 118