30.6.2.6.4 Changing the Top Value

The counter period is changed by writing a new TOP value to the Period register (PER or CC0, depending on the waveform generation mode). If a new TOP value is written when the counter value is close to zero and counting down, the counter can be reloaded with the previous TOP value, due to synchronization delays. Then, the counter will count one extra cycle before the new TOP value is used.

COUNT and TOP are continuously compared, so when a new TOP value that is lower than current COUNT is written to TOP, COUNT will wrap before a compare match.

A counter wraparound can occur in any operation mode when up-counting without buffering, see the figure below.