fritz

Hello zy79

first things first, Profibus DP is just as real time as Profinet RT so changing toProfinet RT won't help (in case MichiJaymeant Profinet IRT, this may help though, but read on as Profibus also has an iscochronous mode).
What may very well help though is going for Isochrone mode to synchronize the various independently running scans/updates (PLC, Profibusetc.) which can explain your problem.
Have a look at the Isochrone Mode manual for more on this.

I hope this helps

 Thanks, fritz. Unfortunately the module does not support Isochrone mode.

TNijpjes

Another trick that could be used is using PIP. Normaly the OB1 update the IO within the set IO range (IW and QW). The Periferie IO is done in it's own cycle (PIW and PQW). By making the counter value's part of a seperate PIP area and linking it to OB35 the counter values will be updated just before calling the OB35. This makes a more stable update time of the counter values.

 I have tried this and the result is same. I will try to use a FM350 and see if there is any improvement.