Modbus TCP
Hi, I have a Schneider PLC configured as a Modbus TCP master of the network and I need to read some memory words from this PLC using a Flexy205, I have already configured as shown in the following document. Is it gonna work?aug-0059-00-poll-data-from-plc-using-modbus-tcp.pdf (786.4 KB)
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Hello Igor,
I would try the following document first:
aug-0078-00-en-poll-data-from-schneider-plc-using-ethernet-procotol.pdf
This is document is dedicated for Schnieder PLC
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igor.silva:I have a Schneider PLC configured as a Modbus TCP master of the network and I need to read some memory words from this PLC using a Flexy205, I have already configured as shown in the following document. Is it gonna work?
You can't read from a master. That's not how modbus works. The master reads and writes and the slave answers.
Modbus
Modbus is a data communications protocol originally published by Modicon (now Schneider Electric) in 1979 for use with its programmable logic controllers (PLCs). Modbus has become a de facto standard communication protocol and is now a commonly available means of connecting industrial electronic devices. Modbus is popular in industrial environments because it is openly published and royalty-free. It was developed for industrial applications, is relatively easy to deploy and maintain compared t Mo...
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Take a look at this post for the answer to your question:
Is the Unity Pro Simulator acting as a Modbus Server/Slave or a Master/Client? I think this is probably a case where you have 2 Masters. You have to set one up as a slave. This document shows how to publish tags in Modbus TCP (as a slave):
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And I'm not understanding why do I have to use the Ecostruxure to monitor the tags through ViewOn.
I have another question, some memory words are for example %MW14269. How should I write the address in flexy when I'm configuring the tags?
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Here is the thing, the system there doesnt use the ecostruxure, so is there any other way?
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I will work on updating that "Publish tags in Modbus TCP" document. It's using the old firmware, but it's the same settings.
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So there is no way to read the data otherwise I change my plc to client?
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In this project I'm just reading, so can I read the data from the other clients? Would it affect my network?
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What about this?
I have another question, some memory words are for example %MW14269. How should I write the address in flexy when I'm configuring the tags?0 -
You stated that your PLC is already configured to act as a Modbus TCP Master which is the same as a Modbus TCP Client. Client and Master are interchangeable. Server and Slave are also the same thing in Modbus TCP.
In Modbus, you can only "read" from a Server/Slave.
In this case, the Flexy can act as a Server/Slave, and you can write the values from the PLC into the Flexy tags. That's what the instructions in PDF are for. I am currently in the process of updating the document for the new firmware, but the settings are the same.
No.
Like I said, you can't read from a Client/Master. That's just how Modbus works.
But in general, Modbus uses a standard addressing scheme. It's up to you to understand what address %MW14269 represents because it's not a standard Modbus address. You need to read the documentation for your PLC. A standard Modbus address would be something like 414269. Here is an example:
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