Difference between PLC cables??????????

Anybody could explain what is the difference between S7 200 cable and S7 300 cable for S7 Siemens PLC?

I know these two cables must convert data signals from computer (RS232) to PLC (RS485) in order to program PLC...but I don't understand why they are different in the catalog...



Thank you for advance

I think the major difference is the impedance of the cables used for the PLCs .

Hello marsu1821;

Both cables are RS-232 to RS-485 converters; but they also function as protocol converters. The S7-200 is programmed with PPI, and the S7-300-400 PLCs are programmed with MPI; there is a difference in speed (PPI is set at 19200 Bauds, MPI at 187,5 kBauds) and of frame structure.
By the way, the electronics of these circuits are one of the best guarded secrets in Siemens' world... do a search on PPI and MPI converters on this site, you will get an idea of the number of collegues requesting the same info as you.
Hope this helps,
Daniel Chartier

alright !
Thank you very much for these informations!
Moreover,I know it's difficult to find informations about this...
I will try to look after the circuit board in the cable in order to do another myself.But I think it will be very difficult.