Overview: FDC PC-E Protocol Converter

Serial Modbus RTU Protocol to Modbus TCP/IP Ethernet Converter



The Ethernet/Serial Converter enables serial devices, such as Future Design Controls FDC-IO Modbus modules communicating on RS232/485 to be connected to a 10/100 Base-TX Ethernet network.

The PC-E Ethernet/Serial Converter can be configured to operate in a number of different modes depending on the application; for additional detail refer to FDC-PC-E_Operating_Modes.html or to Section 2 Operating Modes in the PC-E manual. Each mode allows the PC-E to be configured as a Transparent data link or it can perform the Gateway function of converting Ethernet Modbus TCP messages to Serial Modbus RTU messages and visa versa.

  • Transparent Data Link: Serial [ASCII or Modbus} data sent to the PC-E is encapsulated into an Ethernet packet & sent out on the Ethernet network while data received in an Ethernet packet is removed and sent out its’ serial port; there is no protocol conversion to Modbus RTU or Modbus TCP.
  • Gateway Data Link: Serial Modbus data sent to the PC-E is converted to Ethernet Modbus TCP and data received via Ethernet Modbus TCP is converted and sent out the serial port as Modbus RTU.

The PC-E converters are factory programmed with a default IP address of  This address must be changed before the converter is added to an existing Ethernet network. The IP address in the converter should be unique in the network and can be changed via the Web Server. Web server allows setting IP address, serial data format and operating modes. Most web browsers like Internet explorer, Netscape etc, can access the web server. PC-E supports FTP protocol which enables the web pages to be customized if required.

The web page address for viewing the setup parameters is the web page address for configuring the converter is 

The PC-E converter may be connected to large number of Serial Modbus devices with the technical limit being the number of address’s the networked devices are limited; i.e. Future Design Controls IO Modules have a maximum of 127 modbus addresses while the 300 Series process controls may have address’s up to 255. However, the application needs, configured baud rates / reply timeout, number of polled parameters, (modbus devices and/or the Master’s software typically have a maximum Modbus message length limiting the number of consecutive registers that may be polled in one group communication, i.e. 20, 30, 50, 70, or like the IO Modules, 100), etc. will dictate the appropriate number of Serial Modbus devices comprising one network.

The use of multiple PC-E Converters and duplicate Serial Modbus address's on a system network is possible as the model PC-E’s IP address differentiates between different PC-E converters and their respective Serial Modbus RS485 networks. The master device(s) (PC and/or PLC’s) must be configured with the IP address of the PC-E Converter(s) and with the respective Modbus ID of the Serial Modbus devices. As each Serial Modbus RS485 network is separate (PC-E converter with unique IP address) it is possible to have repeated Modbus ID's on the RS485 networks.


Sample System





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