Clock Generation

In the SPI host operation (CTRLA.MODE=0x3), the serial clock (SCK) is generated internally by the SERCOM Baud Rate Generator (BRG).

In SPI mode, the BRG is set to Synchronous mode. The 8-bit Baud register (BAUD) value is used for generating SCK and clocking the Shift register. Refer to Clock Generation – Baud-Rate Generator for more details.

In SPI client operation (CTRLA.MODE is 0x2), the clock is provided by an external host on the SCK pin. This clock is used to clock the SPI Shift register.