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Does anybody know if Vision controllers (ie V130) support Modbus TCP or do they support the Modbus RTU over TCP implementation. The difference is that the first follows the original Modbus TCP frames (ie no CRC) while the latter encapsulates the serial RTU framing sent over TCP media.

Which one is supported by Vision and the other Unitronics controllers?

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Modbus RTU is not a TCP protocol.  Modbus TCP/IP is designed for sending over an Ethernet network (Vision optional) while Modbus RTU is designed to be sent over a serial network such as RS-485 (Vision standard).  It is common to confuse the data layer with the transport protocol.

Modbus TCP/IP = data layer; Ethernet = transport protocol.

Modbus RTU = data layer; RS-485 = transport protocol.

Modbus TCP/IP can be simplified as Modbus RTU with additional information in the data packet for sending over an Ethernet network.

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I am afraid the answers above are still confusing. Malequardos asked if there is a support for Modbus TCP or for Modbus RTU over TCP. I think the correct answer is: The Vision controllers support Modbus TCP, not Modbus RTU over TCP.
Modbus TCP has its own specification by Schneider. Modbus RTU over TCP is what you get if you use serial / Ethernet converters for Modbus RTU communication. For better understanding, read e.g. this: http://www.simplymodbus.ca/TCP.htm

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could anyone supply a full example of using modbus on the plc side AND on the pc side? 

I would prefer a python example but a .NET is good too.

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Look in the Visilogic Examples for Modbus on the PLC side.

This forum isn't about programming PC applications, but someone may speak up and help.  Your best bet for figuring out Modbus in python is your friend Dr. Google.  The PC will most probably be the Master, and the PLC will most probably be the Slave (or Server in today's politically correct IT-speak).

Like this-

https://stackoverflow.com/questions/17081442/python-modbus-library

Joe T.

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