MODBUS Communication Between Controller and MicroPLC


Thread Starter


I have been struggling to establish communication between field controller with micro PLC 1400 AB and monitoring parameters in SCADA. Field controller output is RS232 . Micro PLC is having message instruction logic. Micro PLC is communicating with SCADA with Ethernet cable. Profibus shielded cable has been used for signal communication. Suggestion is required regarding the matter.
As you've discovered, the task before you is a project. I assume you have a Modbus field device, a Modbus enabled 1400 PLC, and Modbus enabled SCADA.

The field device is almost certainly a Modbus RTU slave.
Therefore, the 1400 has to be a Modbus RTU master on an RS-232 channel.
RS-232 comm settings (baud rate, stop bit, parity) must be identical on both units.
Wiring is critical. I've seen other mention of making sure that the RS-232 is not A-B's DF-1 protocol. caveat emptor.

Scada is usually the Modbus master/client. SCADA is Ethernet/
That makes the 1400 a Modbus/TCP server. You'll have to investigate using the 1400's ethernet port as a Modbus/TCP server.

You need to confirm that the 1400 supports simultaneous Modbus Master functionality on a serial port AND Modbus server functionality on a different port. Some boxes do, some don't. That's a specific device/firmware research project.

A google search brought up an example of configuring a 1400 at this link ( I can't vouch for its accuracy, I haven't done a 1400):