23.4.2.2 Prescaler Selection

The GCLK_TCCn clock is fed into the internal prescaler.

The prescaler consists of a counter that counts up to the selected prescaler value, whereupon the output of the prescaler toggles.

If the precaler factor in the Prescaler bit field in the Control A register (CTRLA.PRESCALER) is above DIV1, the counter update condition can optionally be executed on the next GCLK_TCCn clock pulse or the next prescaled clock pulse. For further details, refer to the description of the CTRLA.PRESCALER bit field and the Prescaler and Counter Synchronization bit field in the Control A register (CTRLA.PRESYNC).

Prescaler outputs from 1 to 1/1024 are available. For a complete list of available prescaler outputs, see the register description for the CTRLA.PRESCALER bit fields.

Note: When counting events, the prescaler is bypassed.

The joint stream of prescaler ticks and event action ticks is called CLK_TCC_COUNT.

Figure 23-2. Prescaler