Siemens 315 crashes when MPI cable is attached


Thread Starter

Tom M

Have had a 315 - 2dp PLC crash twice when the MPI cable is attached. At first I thought it was static, now I don't know what to think. I could find no info on it a Siemens web support.

Has anyone had simaler experience?

Any info as to the cause?

Thanks in advance
Do you have anything else connected on your port? Is it an MPI or DP port? I have experienced this when I plug an MPI cable on a DP port.
The CPU faults if it detects an MPI problem and a certain OB is not present.

You should be able to solve this by downloading the appropriate OB. I'm not sure off the top my head which one it is - something along the lines of "communication error". If you don't manage to find it, post a reply and I'll check in a project for the exact OB number.


Malcolm Bird

Check the 0V line of the power supply to the processor is linked to a proper earth in the panel, sometimes connecting the programmer cable introduces a new earth via the cable/programmer and can cause a power supply dip.
had the problem when using a mpi lead to connect to a DP running at 12 Mbaud. problem solved by buying a profibus comms lead from siemens.