Odd Siemens communications problem.

[JesperMP]

I dont understand what the reserved S7 Basic connectiosn are for. Remove the reservations !

I forgot to ask what is connected to the Profibus network called PROFIBUS(2) ? It seems to be empty.

Apart from that, 3-4 panels plus at least one configured connection may be too much for the slow MPI backplane over which all the comms must pass.
I am beginning to think this is the problem. Since you have intermittent problems already with only 3 panels, it does not seem to have to do with connection resources (the problem wouldnt be intermittent in that case).
If I were in your shoes I would start considering replacing the 316-2DP for a 315-2PN/DP or a 317-2PN/DP (the 315 will probably be performant enough). Then connect all HMIs to the PN port, connect all IO to the DP port (no panels on the DP port !), and keep the CP343-1 for the ISO-on-TCP comms to the other PLC.

Are there MPI partners connected to the MPI port on the 316-2DP ?
- No, both ports are configured as DP.

Then why is one port setup as and connected to MPI in the NetPro screenshot ?

 

[Maugrim]

Hi Jesper, thanks again for your time.


I dont understand what the reserved S7 Basic connectiosn are for. Remove the reservations !

- I tried that before, I increased OP to 7 and decreased S7 Basic to 4. I didn't make any difference.

I forgot to ask what is connected to the Profibus network called PROFIBUS(2) ? It seems to be empty.

- I believe it is used to talk to the other remote PLC. Talks to one PLC via ethernet, other via profibus.

Apart from that, 3-4 panels plus at least one configured connection may be too much for the slow MPI backplane over which all the comms must pass.
I am beginning to think this is the problem. Since you have intermittent problems already with only 3 panels, it does not seem to have to do with connection resources.
If I were in your shoes I would start considering replacing the 316-2DP for a 315-2PN/DP or a 317-2PN/DP (the 315 will probably be performant enough). Then connect all HMIs to the PN port, connect all IO to the DP port (no panels on the DP port !), and keep the CP343-1 for the ISO-on-TCP comms to the other PLC.

- Yes, those are the two we are considering.

Then why is one port setup as and connected to MPI in the NetPro screenshot ?[/QUOTE]

- Thank you for noticing this! All the other PLCs in the plant use both as DP, I didn't notice that it was different in this case. This means I can replace it with a CPU 315-2 DP which is half the price of the 317.

 

[Maugrim]

I changed the PLC a while ago, and all has been fine since.

I think the PLC was faulty from new, as I heard tale of other comm problems they have had over the years...