for(;;){
        usbPoll();

        if (UCSRA&(1<<UDRE)) {
            flag=0;
            if ((dmxcnt&8000)==8000) { //если dmxcnt<0
                if (dmxcnt==(-3)) {UCSRB=UCSRB&247; PORTD=PORTD&253;  }   //выключаем UART, делаем break
                if (dmxcnt==(-2)) {PORTD=PORTD&253;  }  
                if (dmxcnt==(-1)) PORTD |=(1<<1);   //MaB
        } else {
            UCSRB=UCSRB|8;
            UDR=dmxbuf[dmxcnt];
        }
        dmxcnt++;
        if (dmxcnt>dmxlen) dmxcnt=(-3);
        }
    }