Hi all.

I will describe the situation. There was a problem on the Profibus network - the RS-485 repeater was faulty, it was replaced. It was marked 6ES7 972-0AA00-0XA0. Its terminal resistor on the A1B1 network segment was set to OFF, and on the A2B2 segment - ON, which, in my opinion, is wrong (I schematically depicted the network). However, it somehow worked. Therefore, I set the terminal resistors the same way. The repeater that was installed instead of the faulty one is also used and is marked 6ES7 972-0AA01-0XA0 (newer model). After that, the left section of the A2B2 network segment did not work - the Dupline modules (Profibus-DP Type G 3891 0020) were in error. Naturally, I thought that the A2B2 resistor should be set to OFF. So I did. After that, the right section of A2B2 stopped working (I marked it as a LONG LINE), and the error disappeared on the Dupline modules. A very strange situation.. I would be grateful if someone would share their ideas.

And one more question. The old repeater has a network speed switch (you can choose the speed, in our case it is set to position 4, which corresponds to 187.5 Mbps). There is no such switch on the new repeater. Why is it no longer necessary to select the network speed on the new repeater? And there is also the newest model 6ES7 972-0AA02-0XA0. How is it different from 6ES7 972-0AA01-0XA0?

Hello,

The termination switches should be OFF on your repeater, you need them on at the PLC, node 10, node 21 and Node 3.