RTOS/OMAP-L138: OMAP-L138 uPP data lost

Part Number:OMAP-L138

Tool/software:TI-RTOS

I use uPP port for interfacing to tranceiver. Q channel is used for receive data and I channel for transmit.

At startup I enqueue two descriptors for Q and I channels and wait for the EOWI interrupt, then enqueue new descriptors and so on.

The problem: I see lost of data (phase rupture) on receiving, and I the rupture is located in time closed to moment I putting new descriptor:

        uppRegs->UPQD0 = new_frame;
        uppRegs->UPQD1 = (LINES << 16)|(BYTES);
        uppRegs->UPQD2 = BYTES;

I check a lot of uPP usage examples and found nothing that noticeable differs from my code.