5. Each Component Function
74
User’s Manual
Watchdog Timer
The watchdog timer is started by output of A5 to I/O port address 4002h. A second output of A5 to the
same port within the specified expiration time once again triggers the watchdog timer. If a time-out
occurs, a reset or an interrupt is generated according to the 4004h port setting or an alarm is output
according to the 4004h port setting.
The time-out period can be set between 1 - 255 seconds depending on the timer value setting for the
WDT counter port (4003h).
The watchdog timer stops by reading port 4002h. The alarm-out output is cancelled at the same time.
The alarm out is output from the RAS connector's PO2/WDT (pin 12) and cancelled when reset.
The alarm-out output can be set to BIOS startup by BIOS setup (see Chapter 4), watchdog timer startup,
or watchdog timer time-up.
Specifications
-
Time to be set:
1sec - 255sec
-
Interrupt or reset:
Resets or generates an interrupt at time-up (Port setting).
-
External alarm output:
Optocoupler isolated open-collector output (the output status is set by
software). For more information, see the general-purpose I/O
specifications.
-
I/O addresses:
4000h - 4007h (RAS port)
