5. Each Component Function
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 and 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: Opto-coupler insulated 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)
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