10 Watchdog Timer (WDT)/Windowed Watchdog Timer (WWDT)

The WDT/WWDT are special timers designed to detect a deadlock in the microcontroller. If enabled, the software must periodically clear the timer through a specific sequence, or it will reset the microcontroller. If a deadlock occurs, the clearing action will not occur, and thus the microcontroller will reset.

The WDT and WWDT differ in that the WWDT can restrict when the software is allowed to clear the timer. The “Window” feature can require the clearing sequence to be performed within a given time window rather than anytime before the timer rolls over, preventing a deadlock from being undetected by clearing the timer continuously. The figure below shows the difference.

Figure 10-1. Valid Clearing Windows for the WDT and WWDT