32.6.2.3 Clock Generation and Selection
For both Synchronous and Asynchronous modes, the clock used for shifting and sampling data can be generated internally by the SERCOM baud-rate generator or supplied externally through the XCK line.
The Synchronous mode is selected by writing a ‘1
’ to the Communication
Mode bit in the Control A register (CTRLA.CMODE), the Asynchronous mode is selected by
writing ‘0
’ to CTRLA.CMODE.
The internal clock source is selected by writing ‘1
’ to the Operation Mode
bit field in the Control A register (CTRLA.MODE), the external clock source is selected by
writing ‘0
’ to CTRLA.MODE.
The SERCOM baud-rate generator is configured as in the following figure.
In Asynchronous mode (CTRLA.CMODE=0
), the 16-bit
Baud register value is used.
In Synchronous mode (CTRLA.CMODE=1
), the eight
LSBs of the Baud register are used. For more details on configuring the baud rate (see
Clock Generation – Baud-Rate Generator from Related Links).