30.4 Signal Description
| Signal Name | Type | Description |
|---|---|---|
| PAD[3:0] | Digital I/O | General SERCOM pins |
One signal can be mapped to one of several pins. For additional information, refer to Pinout. Using the USART’s I/O lines requires the I/O pins to be configured using the I/O Pin Controller (PORT). When the SERCOM is used in USART mode, the SERCOM controls the direction and value of the I/O pins according to the table below. The PORT Control bit PINCFGn.DRVSTR is still effective for the SERCOM output pins. The PORT Control bit PINCFGn.PULLEN is still effective for enabling or disabling a pull on the SERCOM input pins, but is limited to enabling or disabling of a pull-down only (it is not possible to enable/disable a pull-up). If the receiver or transmitter is disabled, these pins can be used for other purposes.
| Pin | Pin Configuration |
|---|---|
| TxD | Output |
| RxD | Input |
| XCK | Output or input |
The combined configuration of PORT and the Transmit Data Pinout and Receive Data Pinout bit fields in the Control A register (CTRLA.TXPO and CTRLA.RXPO, respectively) will define the physical position of the USART signals as shown in the preceding table.