Watchdog Window

The Windowed Watchdog Timer has an optional Windowed mode that is controlled by either the WDTCWS Configuration bits or the WINDOW bits. In the Windowed mode (WINDOW < ‘b1111), the CLRWDT instruction must occur within the allowed window of the WDT period. Any CLRWDT instruction that occurs outside of this window will trigger a window violation and will cause a WWDT Reset, similar to a WWDT time-out. See Figure 1 for an example.

When the WDTCWS Configuration bits are ‘b111, then the window size is controlled by the WINDOW bits, otherwise the window size is controlled by the WDTCWS bits. The five Most Significant bits of the WDTTMR register are used to determine whether the window is open, as defined by the window size. In the event of a window violation, a Reset will be generated and the WDTWV bit of the PCON0 register will be cleared. This bit is set by a POR and can be set by software.