for the right connection (with Profibus connector) to the S7 200 side connect A1- B1 and termination resistor on the ON position, also on the side of the panel connect A1- B1 and termination resistor on the ON position

Could you elaborate as to why the termination resistor need to be on both side please?

Termination resistors are normally to prevent signal reflections which can cause false signals. Any line has a characteristic impedance and, depending upon the frequency of the signal being sent and the length of the line, the line may need to be terminated with a resistor equal to its characteristic impedance to avoid problem reflections.

Reflections are caused when the energy in the pulse propagating down the line is not completely absorbed by the load at the end of the line. For example if you have a 5V pulse traveling down a line with a 50Ω characteristic impedance, the power contained in the pulse is 5²/50 = 0.5W. If that pulse sees any load impedance other than 50Ω at the end of the line, then not all the energy in the pulse is absorbed. The excess will be reflected back down the line.

Using the siemens profibus plugs with both ends connected to the left hand side and the terminating resistors on I still cannot get it to connect to s7-200 PCU 266.( PLC port 0 and IF1B on screen.)

I have uploaed a screen shot the the coms set up on pro tool.

Thanks

Any takers for the above??

Help would be very my appreciated

Thanks