Connecting a modern PC to a legacy Modicon PLC requires specific hardware. Required Hardware

For Modbus Plus networks, you historically needed a bulky PCMCIA PCMK card. On modern PCs, this is impossible. Instead, look for a Modbus Plus to Ethernet bridge (e.g., ProSoft or Moxa) or use a legacy industrial PC from the early 2000s running Windows 2000.

The Enduring Legacy of Industrial Automation: Navigating Modsoft 2.6 Download and Usage

: Modern PCs lack native COM ports; you will likely need a high-quality USB-to-Serial adapter and potentially a RS-232 to RS-485 converter depending on your PLC model.

To connect online with a Modicon 984 or Quantum PLC, DOSBox must map your physical USB-to-Serial adapter to a virtual COM port. Open the dosbox.conf configuration file on your computer. Locate the [serial] section.