19.3.2.3 Configuration Protection and Lock

The WDT provides two security mechanisms to avoid unintentional changes to the WDT settings:

The first mechanism is the Configuration Change Protection mechanism, employing a timed write procedure for changing the WDT control registers.

The second mechanism locks the configuration by writing a '1' to the LOCK bit in the Status register (WDT.STATUS). When this bit is '1', the Control A register (WDT.CTRLA) cannot be changed. Consequently, the WDT cannot be disabled from software.

LOCK in WDT.STATUS can only be written to '1'. It can only be cleared in debug mode.

If the WDT configuration is loaded from fuses, LOCK is automatically set in WDT.STATUS.