What serial communication modes does the COM port support, and how do I switch between them?

The COM port (DB9 J1) supports RS232, RS422, and RS485 modes, with the default mode being RS485. You switch modes by toggling the DIP switch (SW3), and this must be done after powering off the device to avoid damage. RS232 comes with flow control, and the full mode selection table is controlled by three switch positions (Mode_0, Mode_1, Mode_2). (Page 11-12)