Hello Jery;

For a S7-300 CPU to operate as a Modbus/TCP client, you must download and license one of  the Open Modbus/TCP drivers shown in the following document:

How do you establish a Modbus/TCP communication from a SIMATIC S7-300/S7-400 and where can you find further information?

https://support.industry.siemens.com/cs/ww/en/view/22660304

I would suggest you select the driver for Modbus/TCP over the integrated Ethernet port of the CPU, 6AV6676-6MB20-3AX0. Connection between the CPU and the Modbus server (your weigh belt blender) is either though a standard Ethernet cable or you can use a switch betwen the two.

You will find at the bottom of the link page demo versions of the drivers that you can use for the development of your project. You are expected to license the driver properly when you are ready to give it to the client; notice that while you are in demo mode the Modbus/TCP software will cause a SF LED to light up, and the diagnostic buffer will fill up with error messages until the license is applied (and the client is not happy when the CPU is showing faults continuously and might not accept this CPU...)

Hope this helps,

Daniel Chartier