49.5.3 Clocks
The TCC bus clocks (CLK_TCCx_APB) can be enabled and disabled in the Main Clock module. The default state of CLK_TCCx_APB can be found in the Peripheral Clock Masking section (see the Related Links below).
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.
The generic clocks (GCLK_TCCx) are asynchronous to the bus clock (CLK_TCCx_APB). Due to this asynchronicity, writing certain registers will require synchronization between the clock domains. Refer to Synchronization for further details.