communication between S7-313c & Wincc 6.2 on MPI

[rsgarg]

Hi,
I have a arrangment of 13nos TP177A HMI , 13 Nos S7-313C CPU's & WINCC 6.2 on MPI network, My problem is wincc communication is break for few seconds continuse.[FONT=&quot]if I shut one CPU ( CPU supply Off) the communication failure interval is increased, if we shut two CPU then there is no communication failure. Please help how to overcome this communication failure.
Thanks in advance
[/FONT]

 

[KalleOlsen]

Hi,
I have a arrangment of 13nos TP177A HMI , 13 Nos S7-313C CPU's & WINCC 6.2 on MPI network, My problem is wincc communication is break for few seconds continuse.[FONT=&quot]if I shut one CPU ( CPU supply Off) the communication failure interval is increased, if we shut two CPU then there is no communication failure. Please help how to overcome this communication failure.
Thanks in advance
[/FONT]

The MPI-bus must be treated exactly like a Profibus installation. Both are RS485.

Do you use the violet profi cable?
The proper profi plugs?
End termination?
Do you have a proper earthing of the cabinets? Big square cupper!
Proper equipotential connection between them? Big square cupper!
The PC must also be earthed and tied to the same equipot.
No power cables close to the bus cable?
Did you follow the profibus installation guidelines, from www.profibus.com ?


Kalle

Here's a former thread about diagnosis:
http://www.plctalk.net/qanda/showthread.php?t=64643&highlight=profibus+problem

 

[JesperMP]

MPI @187.5k isnt very performant.
Connecting 13 PLCs to MPI will mean you cannot have a very intensive datatransfer per PLC.
You can try to increace the update interval (try 2 seconds !), and if possible to reduce the number of tags.

Apart from that, also be aware that the MPI port on the 313C cpu does not have galwanic isolation to the bacplane. For this reason, Siemens recommends max 50 meters for the complete network, or use repeaters. I also think there is a limitation of max 12 stations per segment.

 

[rsgarg]

Hi JesperMP,

Thanks, I will Try Repeter today.

 

[rsgarg]

Hi,

Ihave tried with RS485 Reapeter but problem is same, kindly suggesst more to do.

Thanks

R.S.Garg