Profibus network Dropping out

Hi all,

Using a Prosoft MVI56PDPMV1(Profibus node 5)with a 1756 - L61 CPU.

The network consists of 3 identical slaves (profibus node 1,2,3).

I have setup the data transfer and it works fine. I get all the relevant data between the slaves and the PLC.

My issue is that the network drops out randomly. When this happens all my data goes to 0 for about 1 second,then without intervention the network recovers and all data is available again.

The network is only about 10mtrs in length, running at 500kbit/sec (prosoft module reports it is capable of running at 12000kbit/sec) Terminating resistors are switched on at Prosoft module end and last slave end.

The Prosoft online network monitor shows correct status of modules (green when ok and red when network drops out).

We have tried grounding all the shields at each device, but this didnt seem to make any difference.

I am just asking here first to see if anyone has had similar issues, because i am not sure if it is network or actual config of Prosoft module.

Next step i think would be to get in touch with Prosoft.

Thanks in advance for any responses.

I would
Replace the cables and connectors.
Check that the common ground is OK.
Possibly drop the baudrate to 187.5k.
Possibly install one active terminator at the end, and let it be supplied from the same 24V as the Profibus master.

Thought i would post an update in case someone else gets a similar problem.

Contacted Prosoft - and after a bit of testing turned out to be the RPI time was set at 5ms for the Prosoft module. Set it to 80ms and network is now stable with no drop outs. Prosoft module is located in a remote rack over Controlnet. It appears to have been a bandwidth issue.