Hello everyone, I'm trying to establish a Modbus TCP/IP connection between a SCHNEIDER TM251MESE PLC and a Siemens WINCC UNIFIED SCADA. I'm having trouble transferring real or DINT data to it. Has anyone experienced this type of problem? Thank you very much.
Have you tried asking on a Siemens or Schneider forum? Your question is allowed in this forum's general category, but you might have better results elsewhere.
Yes, and they haven't been able to give me a concrete answer about the problem.
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In my totally unbiased opinion, your best option would be to start using Ignition SCADA instead. 
/s
In all seriousness, I'm not sure how many Siemens or Schneider exerts we have on the forum. That being said, I'd be happy to help (as much as I can) troubleshoot basic Modbus issues.
You mention that you're trying to establish a Modbus TCP/IP connection, and that you're having trouble reading/writing REAL and DINT values. What exactly are you seeing? Are you able to connect? Is there an error when attempting to read or write?
With the writing and reading of integers I have no problems in fact if I for example take MW100 as an integer in the PLC and in the SCADA I configure it in register 4×400101 since in Siemens the address starts at 101 it does it correctly I can send numbers from the SCADA or vice versa. Now my problem with the DINT / REALS since in PLC it is addressed as %MD. For example if I address a real in %MD200 by criterion I would use the SIMPLE word MW201 AND MW200 and in SCADA it would be the floating point 4x400201 but I don't see any transfer of anything. In the PLC by forcing the value it writes it but does not transmit anything, that is to say that if I want to read a temperature it is not doing it.
Can you get a packet capture using Wireshark to take a look at the requests and the responses between the two? Feel free to share the capture file here. Try to include requests for tags that are working and tags that are not working.
Hello everyone, I've now been able to connect via Modbus TCP/IP. I've also tried another alternative, which is to use the PLC as a server, essentially using the OPC UA protocol.
Thank you very much.
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