53.6.2.5 Period Control

The Channel Compare 0 register (CC0) can act as a period register (PER) by writing the PEREN bit in the Control A register (CTRLA.PEREN) to '1'. The PER can be used to control the top value (TOP) of the counting operation:

When up-counting and the counter reaches the value of CC0, the counter is cleared to zero. When down-counting and the counter reaches zero, the counter is reloaded with the CC0 value.