thank you all for quick responses. After your suggestions and contact with Unitronics support I created a final version of my program.
Unfortunately, there are no received messages. Messages are received only during power-up of the converter (some noise).
I checked my cable - there is galvanic connection between pins and endings. I also swapped cables many times.
Here is the oscillogram of the Modbus signal at drive inputs.
And below oscillogram when I connect with my testing software (and it works). I know that probe's polarization is inversed. What concerns me is that the amplitude of peak-peak voltage above is 2.5V when it is 7V below.
Modbus in my drive works properly as I checked it by modbus testing software on my PC (checking means sending and receiving words and operating drive remotely). BTW. Mtester - great and free software. Register which I try to read (2101 in drive, so 2100 in PLC) has value 65 - no matter as there are no received data.
MI 2 status is 4 and 5 alternately.
Termination is done at both ends.
Do you have any other ideas?
Once more - when I want to set PLC Net ID with this block, numbers from 1-63 are CANopen and from 64 RS485? Does it have meaning? In my program, PLC is 1 when drive is 2. I tried also 64 and 65 with no success.