The Counter period is changed by writing a new TOP value to the Period (TCAn.PER) register.
No Buffering: If double-buffering is not used, any period update is immediate.
Figure 1. Changing the Period Without
Buffering
A counter wrap-around can occur in any mode
of operation when counting up without buffering, as the TCAn.CNT and TCAn.PER registers are
continuously compared. If a new TOP value is written to TCAn.PER that is lower than the
current TCAn.CNT, the counter will wrap first, before a compare match occurs.
Figure 2. Unbuffered Dual-Slope
Operation
With Buffering: When
double-buffering is used, the buffer can be written at any time and still maintain the
correct operation. The TCAn.PER is always updated on the UPDATE condition, as shown for
dual-slope operation in the figure below. This prevents wrap-around and the generation of
odd waveforms.
Figure 3. Changing the Period Using
Buffering
Note: Buffering is used in figures illustrating TCA operation if not otherwise
specified.