33.6.4 Time Delays During Wake-up

There will be a time delay between the WDT event in Sleep and the beginning of code execution. The duration of this delay consists of the start-up time for the oscillator in use. Unlike a wake-up from Sleep mode, there are no time delays associated with wake-up from Idle mode. The system clock is running during Idle mode; therefore, no start-up delays are required at wake-up.