13.24.6.2.2 Enabling, Disabling, and Resetting
The TCC is enabled by writing a '1' to the Enable bit in the Control A register (CTRLA.ENABLE). The TCC is disabled by writing a zero to CTRLA.ENABLE.
The TCC is reset by writing '1' to the Software Reset bit in the Control A register (CTRLA.SWRST). All registers in the TCC, except DBGCTRL, will be reset to their initial state, and the TCC will be disabled. Refer to the Control A (CTRLA) register for details.
The TCC should be disabled before the TCC is reset to avoid undefined behavior.