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 20-6. 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 20-7. Unbuffered Dual-Slope
Operation
With Buffering: When
double-buffering is used, the buffer can be written at any time and still maintain 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 20-8. Changing the Period Using
Buffering
Note: Buffering is used in figures illustrating TCA operation if not otherwise
specified.
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