The dual RS-485 option module adds two COM ports on the installed FX80 controller. The controller has two onboard RS-485 ports. In the station running on the controller, these two ports always operate as COM1 and COM2.
Installed serial option modules (RS-232 or RS-485) continue COM port numbering based on proximity to the controller, where the option module closest to the controller base operates as the next available serial COM ports.
For example, if attached directly to the controller, this dual RS-485 option module operates as COM3 and COM4. If another RS-485 option module is attached to it, the second module operates as COM5 and COM6.
