20.3.1 Initialization

• The WDT is enabled when a non-zero value is written to the Period bits (PERIOD) in the Control A register (WDT.CTRLA).
• Optional: Write a non-zero value to the Window bits (WINDOW) in WDT.CTRLA to enable Window mode operation.

All bits in the Control A register and the Lock bit (LOCK) in the STATUS register (WDT.STATUS) are write protected by the Configuration Change Protection mechanism.

The Reset value of WDT.CTRLA is defined by a fuse (FUSE.WDTCFG), so the WDT can be enabled at boot time. If this is the case, the LOCK bit in WDT.STATUS is set at boot time.