TIA portal - modbus tcp

Varri · May 5, 2022

Hi!

Science we don’t get any ready-to-go modbus functions from my Siemens I wanted to ask you TIA users:

In your experience, what’s the best practice for modbus with Siemens?

L D[AR2P#0.0] · May 5, 2022

Modbus blocks are in the comms section of the instructions. I've just used them to talk to a nidec drive.

drbitboy · May 5, 2022

The TIA instructions are MB_SERVER and MB_CLIENT, I think.

Here are a couple of Github repos that have an S7-1200 acting a Modbus server using the MB_SERVER instruction; I imagine the Modbus client instruction would be similar.

https://github.com/drbitboy/PLC_Modbus_client_server_50words

https://github.com/drbitboy/PLC_Modbus

goghie · May 5, 2022

Just to add that Siemens is pretty sh***y with Modbus implementation as it doesn't support function 23H ( read and write multiple registers)

danw · May 6, 2022

goghie said:
Just to add that Siemens is pretty sh***y with Modbus implementation as it doesn't support function 23H ( read and write multiple registers)

Which commercial Modbus Master/clients do support Function Code 23H? I have yet to run into one that does.

There are slave/server devices that support FC 23 and there's one odd-ball that supports only FC 23, which display a remarkable ignorance of market conditions in my opinion.

goghie · May 6, 2022

@danw
Most HMIs and VFDs I use support it. Mitsubishi and Codesys based PLC use it. It makes life much easier for programmer when you can read and write in one cycle.

TIA portal - modbus tcp

Varri

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