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S7-300 Cable Assembly (Pinouts) for MPI and Profibus
Looking for any pdf manuals showing the cable assembly (Pinout) used to comunicate the PC with the MPI
By Luciano Vasconcelos on 5 June, 2002 - 2:20 pm

I am looking for any pdf manuals showing the cable assembly (Pinout) used to comunicate the PC with the MPI and the other port configuration , i mean profibus. Can somebody help me.

By Daniel Chartier on 6 June, 2002 - 10:04 am

Hello, Luciano;
the following address will bring you to a Siemens info page on Profibus (and MPI) connectors:


For very short distances (5 m. max) and low speed (187,5 kB on MPI, 1,5 MB on Profibus), we have setup Sub-D 9 pin connectors with straight RS-485 connections: pin 8 to pin 8, pin 3 to pin 3, pin 5 to pin 5. It works, but we can only do a point to point (1 master, 1 slave) conection. I do not recommend this configuration for anything else than a test set-up.

Look on "": for manufacturers of Profibus cable and connectors, and get the cheapest if you must; but get something certified. It is the least yopu can do for your clients, and it removes one uncertainty level in your diagnostics.

Hope this helps,
Daniel Chartier

By Konrad Heidrich on 6 June, 2002 - 2:46 pm

the following list shows the pinning of a Profibus/MPI interface (out of the Profibus spec).

To connect MPI with a PC you need a Profibus card in your PC or a MPI Adapter - MPI to RS232 (e.g. SSW7 from - or a NetLink - MPI to TCP (e.g. NetLink from Helmholz).

Pin1 Shield (3)
Pin2 M24V (2)
Pin3 RxD/TxD-P (x)
Pin4 CNTR-P (3)
Pin5 GNDD (x)
Pin6 V5P (1)
Pin7 P24V (2)
Pin8 RxD/TxD-N (x)
Pin9 CNTR-N (4)

(x) Minnimum needed for Profibus and MPI bus
(1) Needed at the ends of the bus (for termination)
(2) only necessary for power supplying your device out of the plc
(3) not neccessary
(4) useless (I do not know one device on the market with this pin connected!)

For further information feel free and contact me at

Best regards,

By Gabriele Corti (Varese Italy) on 6 June, 2002 - 2:58 pm


Pinout of the Sub D Connector (PG/OP Connector)
The 9-pin sub D connector has the
following pinout:

+ Pin No.+-Signal Name+-Meaning++++++++++++++++++
+ 1 + + +
+ 2 + M24V + Chassis 24 V +
+ 3 + RxD/TxD-P + Data line B 9 4 +
+ 4 + RTS + Request To Send +
+ 5 + M5V2 + Data ref.vol.(of station)+
+ 6 + P5V2 + Pwr plus (from station)2 +
+ 7 + P24V + 24 V 1 +
+ 8 + RxD/TxD-N + Data line A +
+ 9 + + +

The name of manual from where I have taken this document is Profn_e.pdf and can be found on the "www.Ad.Siemens.De":http://WWW.Ad.Siemens.De site. The link for Mpi should be the same, if you execute a Point To Point link you pay attention to the terminators resistances which must be On.

Ciao Gcor

I suggest that you go to "": and type in the Entry ID 10420976. I believe you will find all the information you require.