A Watchdog Timer (WDT) is a system timer that generates a Reset if the firmware does not
issue a CLRWDT
instruction within the time-out period. A Watchdog Timer
is typically used to recover the system from unexpected events. The Windowed Watchdog
Timer (WWDT) differs from nonwindowed operation in that CLRWDT
instructions are only accepted when they are performed within a specific window during
the time-out period.