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joshi171

Modbus TCP/IP communication

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Hello everyone, I am new to the automation and communication industry. I have a query regarding the TCP/IP communication. I am using Siemens PLC which supports TCP/IP protocol. The PLC is communicating to a server in control room and server again is connected to the existing centralized network through switch. Now we have to connect some additional pumps into our PLC. These pump controller supports Modbus over TCP/IP protocol and it has RJ45 connectivity as well. I need to connect them such a way so that there is no disturbance in the existing centralised network related to IP conflicts. Suggest me the best possible way to connect those pumps. Thanks in Advance

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Hello, I do not have an answer for your question but, you said something that you should be aware of because it could be a problem. "These pump controller supports Modbus over TCP/IP protocol..." MODBUS TCP/IP and MODBUS over TCP/IP are two different protocols. Many people shorten MODBUS RTU over TCP/IP and say MODBUS over TCP/IP. MODBUS RTU over TCP/IP is the MODBUS serial protocol packetized for TCP. MODBUS TCP is a different protocol from MODBUS RTU over TCP/IP and the two do not work together. Just a heads up.

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Hello, I'am using modbus tcp, modbus and modbus+ every day. Sometime people calling modbus tcp as modbus over TCP/IP - but it's the same. Siemens PLC supports TCP/IP protocol, but may be not the Modbus TCP, modbus TCP and TCP/IP is not the same.

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>Sometime people calling modbus tcp as modbus over TCP/IP - but it's the same. Not if it is MODBUS RTU over TCP/IP.

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As far as I know Siemens does not offer Modbus/TCP. Their Ethernet is a different protocol.

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Hello, Right. Siemens native protocol is not MODBUS TCP. I have been told Siemens sales a MODBUS TCP software add on. And you could roll your own.

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