19.6.1 WDT Operation in Power-Saving Modes
The WDT can be used to wake the device from the Standby Sleep or Idle modes. The WDT continues to operate in the Power-Saving modes. A time-out can, then, be used to wake the device. This allows the device to remain in Standby Sleep mode until the WDT expires or another interrupt wakes the device.
If the device does not re-enter the Standby Sleep or Idle mode following a wake-up, the WDT must be disabled or periodically serviced to prevent a device Reset.