Ewon - Siemens S7-300 Application


I am trying to figure out if I can use a flexy or something else to communicate with a S7-300 DP Master and exchange tags/values. I know flexy supports Modbus/TCP output so I would like to get instrument data into the flexy over the MPI connection with the processor and then convert to Modbus TCP. Is this possible?

The PLC I am working with is 6ES7315-2AH14-0AB0 which is a Class 1 master on the DP Network

See the attached screenshot for reference.

Network Diagram attached. hardware.bmp (5.7 MB)


From your diagram I see the modbus TCP/IP is on the WAN side. the picture may be a mistake but if you want to pull the published modbus data from the Flexy then it will need to be coming from the LAN port.

To get the S7-300 tags to Modbus you will need to create the S7-300 tags in the Flexy then you can enable Modbus TCP and choose the registry you want to publish for each given tag.

I have attached are page with are Siemens documentation and also the document on modbus TCP publishing.


Hello, I’d like to add a comment to this post. It is possible to access the Modbus-TCP registers from the WAN network. However it does require that the Security settings be modified. In the Flexy’s left menu, navigate to “Setup > System > Communication > Security”. Then set the “WAN protection level” to “Allow all”. You must reboot the Flexy for this change to take effect.

Best regards,