The desired serial interface option board type for the desired option board slot must be selected and added.

The option board may require some other channel configuration according to your need.

Following example shows how to add a TA5142-RS485I isolated interface and the desired protocol.

The desired protocol has also to be added according to your needs, e.g. Modbus RTU client:

The parameter for the serial interface can also be adapted like baudrate, data bit, stop bit or parity.