34.5.3 Clocks

Two generic clocks are used by SERCOM, GCLK_SERCOMx_CORE and GCLK_SERCOMx_SLOW. The core clock (GCLK_SERCOMx_CORE) can clock the I²C when working as a host. The slow clock (GCLK_SERCOMx_SLOW) is required only for certain functions, for example, for SMBus timing 32KHz_LPCLK must be configured as this is the source for GCLK_SERCOMx_SLOW clock. These two clocks must be configured and enabled in the CRU registers before using the I²C.

These generic clocks are asynchronous to the bus clock (PBx_CLK). Due to this asynchronicity, writes to certain registers requires synchronization between the clock domains.