Thank you very much for your interest on my problem, Richard!
To the bus cable is connected only 1 device - USB to RS485 adaptor. Pins 2,3,4,5 (RO, RE,DE,DI) are connected to ADSP21369 processor. Nothing more is connected to this chip.
Pins DE and /RE were configured in my program only once - during initialization of device. These pins were configured so, that DE pin is always HIGH and /RE pin is always LOW.
When DE and /RE pins are both HIGH or LOW, there are no problem with sending and receiving data.
There are 4 files in my attachments. Files TEK0000 - TEK0002.jpg - sending data from ADSP processor to PC. File TEK0003.jpg - sending data from PC to ADSP processor.
Best regards,
Viacheslav