5. Each Component Function
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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 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 (12-pin) 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 to 255sec
-
Interrupt or reset
: Resets or generates an interrupt at time-up (Port setting).
-
External alarm output
: Opto-coupler isolated open-collector output (the output status is
set by software). For more information, see the general-purpose
I/O specifications.
-
I/O addresses
: 4001h to 4005h (RAS port)
