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PCA-6289 User’s Manual 46

Appendix A Programming the watchdog

A.1 Programming the Watchdog Timer

The PCA-6289'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 Working Procedure

Watchdog Timer (WDT) is a special hardware device that monitors the

computer system during normal operation. WDT has a clock circuit that

times down from a set number to zero. If a monitored item occurs before

the timer reaches zero, WDT resets and counts down again. If for some

reason the monitored item doesn’t occur before

the timer reaches zero, WDT performs an action, such as a diagnostic

operation (rebooting the computer). You must enter timer values into

WDT Configuration Register (Write the control value to the Configura-

tion Port), and clear WDT counter (read the Configuration Port).

A.1.2 Watchdog Timer Control Register

The Watchdog Timer Control Register controls the WDT working mode.

Write the value to the WDT Configuration Port. The following table

describes the Control Register bit definition:

Table A.1: Installing the heatsink

WDT Configuration port F2 Default at F2

Watch Dog Timer Disabled Default at disabled

Enabled Enabled for user's

programming

WDT Active Time 1 sec

2 sec

4 sec

8 sec

16 sec

32 sec

64 sec

128 sec

Default at 64 sec

1 2 ... 51 52 53 54 55 56 57 58 59 60 61 ... 67 68

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