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PCA-6189 User’s Manual 100
Appendix A Programming the watchdog
A.1 Programming the Watchdog Timer
The PCA-6189's watchdog timer can be used to monitor system software
operation and take corrective action if the software fails to function after
the programmed period. This section describes the operation of the
watchdog timer and how to program it.
A.1.1 Watchdog timer overview
The watchdog timer is built-in the super I/O controller W83627HF. It
provides the following functions for user programming:
• Can be enabled and disabled by user's program.
• Timer can be set from 1 to 255 seconds or 1 to 255 minutes.
• Generates an interrupt or resets signal if the software fails to reset the
timer after time-out.
A.1.2 Reset/ Interrupt selection
The J2 jumper is used to select reset or interrupt (IRQ 11) in the event the
watchdog timer is tripped. See Chapter 1 for detailed jumper settings.
A.1.3 Programming the Watchdog Timer
The I/O port address of the watchdog timer is 2E(hex) and 2F(hex).
2E (hex) is the address port. 2F(hex) is the data port.
You must first assign the address of register by writing address value
into address port 2E(hex), then write/read data to/from the assigned
register through data port 2F (hex).
Note: The interrupt output of the watchdog timer is a low
level signal. It will be held low until the watchdog timer
is reset.