41.5.3 Clocks
A generic clock (GCLK_TCCx) is required to clock the TCC. This clock must be configured and enabled in the generic clock controller before using the TCC. Note that TCC1 and TCC2 share a single peripheral clock generator.
The generic clocks (GCLK_TCCx) are asynchronous to the bus clock (PB1_CLK). Due to this asynchronicity, writing certain registers will require synchronization between the clock domains.