23.5.1 I/O Lines
Using the SERCOM I/O lines requires the I/O pins to be configured using port configuration (PORT).
The SERCOM has four internal pads, PAD[3:0], and the signals from I2C, SPI and USART are routed through these SERCOM pads via a multiplexer. The configuration of the multiplexer is available from the different SERCOM modes. Refer to the mode specific chapters for details.