New Modbus/TCP Gateway Feature (Only on Super PLC models with r77 or higher Firmware)
With r77 firmware or higher, any Nano-10, FMD series, or F-series PLC can now be configured as a Modbus TCP gateway. This is of course particularly useful in PLC set-ups where most of the PLCs need Ethernet link-up into broader networks but as in most cases, are equipped only with traditional and standard serial communication ports (such as RS232 and RS485).
Once configured as a gateway, the PLC will be able to receive Modbus TCP commands from a client device or software (from the LAN or Internet) and transparently convert them to Modbus RTU (serial) and send them out of the COM port that was configured. The PLC will only convert and redirect Modbus TCP commands if the specified ID is different from the Gateway PLCs ID.
If the incoming Modbus TCP command is addressed to the Gateway PLC, then it will accept and process the command as per normal.
If the incoming Modbus TCP command has an ID that is different from the Gateway PLC, then it will do the following automatically and transparently:
1. Convert the command to Modbus RTU (serial)
2. Send it out of the COM port that was configured to the specified device ID.
3. Wait for a response and, once received, convert it from Modbus RTU back to Modbus TCP.
4. Send the response in Modbus TCP format back to the client that sent the command originally.
For more reading on this capability, you can download : http://www.lt-automation.com/ModbusGatewayFunction.pdf