Hello Mokha;

We need a bit more information.

What CPU, what slave exactly? How didyou setup the data exchange between the 2, a screenshot of the hardwate configuration would be helpful.

Any active diagnostic LEDs on the CPU, on the slave? Any related messages in the diagnostc buffer of the CPU?

Hope this helps,

Daniel Chartier 

maybe the slave maybe the data you send, maybe the fw of the s7-300

why not simple first give little more exact infirmation which devices you use, which dat, which engineering.

this can help to analyze the problem, only say S7-300 and a PROFIBUS SLAVE  is not very informative

Hello Mohka;

I found a description of the Profibus protocol for the W-series from Laumas here:

- Laumas W-series Communication protocols (Profibus, pages 54- 76)

https://www.nikcell.com/images/productFiles/User%20Manual%20Communication%20Protocols%20for%20W%20Series%20(PDF).pdf

I could not locate a sample program for Laumas sytems on Profibus, but I did find one for Profint on Youtube.Do not panic, the data exchanges on Profinet and Profibus are identical, and you can see how to define the exchange structures if you look at time stamp 7:45 in he video, compared to the screenshot below taken from the Communication protocols manual, pages 69-70.

https://www.youtube.com/watch?v=KyqZvCQBOoc&list=PLiK21gMA_86QaqfB4w1gWFbu-mQOElGv0&index=19

Show us how the data exchanges have been setup in your PLC program, that would be a first step in getting this working. Follow the example for Profinet to understand how data is read and written to he Laumas batch weighting system over Profibus.

Hope this helps,

Daniel Chartier