Serial communication is faciliated by addition of the Serial device in E-Prime.
You can add the Serial device to your experiment via the Devices tab of the Experiment Object's property pages. Addition of the Serial Device on the Experiment Object allows you to specify port settings for the Serial Device directly on the Experiment Object.
Once you have added the Serial Device, you will still need to use E-Basic script within an InLine for communication with the serial port. The Serial device's properties and methods have been fully documented in the Serial Device Object topic in the OnLine E-Basic Help. You can also find a sample experiment, demonstrating use of the Serial device, in the Samples area of v1.0 web support.
Note that if you plan to use the Serial Device, you may need a null modem connected to your serial port to properly handle the data being passed through the port.