The simplest CitectSCADA systems use a single computer connected to the I/O Device(s). You can connect an I/O Device directly to a communications portPC port used for sending and receiving serial data (also called serial or COM ports). with a standard RS-232 communications cable.
How to set up CitectSCADA to use your computer's COM port:
Note: You only need to define the COMx board once. You can then add several ports that use the same CitectSCADA board. For example, a COM port and two serial boards could be defined as one COMx board in CitectSCADA, with multiple ports.