When the microcontroller first powers on or wakes up from Deep Sleep, it will start executing code from the Reset vector. If the RTCC is using the secondary oscillator to keep track of time, the secondary oscillator should be enabled before clearing the Deep Sleep release bit. This allows the RTCC to continue operating continuously, without losing time. Deep Sleep hardware will keep the RTCC and secondary oscillator running throughout Deep Sleep and wake-up, but firmware needs to re-enable the RTCC on wake-up so that the module doesn’t get disabled when the Deep Sleep release state bit is cleared. Applications that are not using the real-time clock can skip this step.