21.3.3.1 Normal Mode

In the Normal mode operation, a single time-out period is set for the WDT. If the WDT is not reset from software using the WDR instruction during the defined time-out period, the WDT will issue a system Reset.

Each time the WDT is reset by software using the WDR instruction, a new WDT time-out period starts.

There are 11 possible WDT time-out periods (TO_WDT), selectable from 8 ms to 8s by writing to the Period (PERIOD) bit field in the Control A (WDT.CTRLA) register.

The figure below shows a typical timing scheme for the WDT operating in Normal mode.

Figure 21-2. Normal Mode Operation

The Normal mode is enabled as long as the Window (WINDOW) bit field in the WDT.CTRLA register is ‘0x0’.