10 WWDT - Windowed Watchdog Timer

The 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. The Watchdog Timer is typically used to recover the system from unexpected events. The Windowed Watchdog Timer (WWDT) differs in that CLRWDT instructions are only accepted when they are performed within a specific window during the time-out period.

The WWDT has the following features:

  • Selectable Clock Source
  • Multiple Operating Modes
    • WWDT is always on
    • WWDT is off when in Sleep
    • WWDT is controlled by software
    • WWDT is always off
  • Configurable Time-out Period is from 1 ms to 256s (Nominal)
  • Configurable Window Size from 12.5% to 100% of the Time-out Period
  • Multiple Reset Conditions
Figure 10-1. Windowed Watchdog Timer Block Diagram