20.4.2 Operation
The WDT is a continuously running counter configured to a predefined time-out period. Before the end of the time-out period, the WDT must be cleared, otherwise, a system Reset request is issued.
The WDT can be configured in Normal mode or Window mode, both offering the option of early warning interrupt generation. The settings in the Control A (CTRLA) register and the Interrupt Enable register (handled by INTENCLR/INTENSET) determine the mode of operation. The description for each of the modes is given in the following sections.
| Mode | CTRLA.ENABLE | CTRLA.WEN | Interrupt Enable |
|---|---|---|---|
| Stopped | 0 | x | x |
| Normal mode | 1 | 0 | 0 |
| Normal mode with early warning interrupt | 1 | 0 | 1 |
| Window mode | 1 | 1 | 0 |
| Window mode with early warning interrupt | 1 | 1 | 1 |
When enabled, the WDT will run in active mode and all sleep modes. It is asynchronous and runs from a CPU-independent clock source. The WDT will continue operation and issue a system Reset request or interrupt even if the main clocks fail.