Timer0 Overflow Interrupt löst nicht aus (ATmega16)

[schamp]

Code while()

while(1)
  {
    if (bRxFlag & RX_M_RECEIVE)
    {
       if    ( ( PIND & (1<<PD2))  ^  (bOld & (1<<PD2)))  // any Flanke ?
       {
              if (bCnt & 0x08)
              {
                  bRxFlag &= ~RX_M_RECEIVE;
                  bRxFlag |= RX_M_DATA;
              }
              else
              {
                   bOld = PIND;
                   bCnt++;
                   bRxByte >>= 1;
              }
        }
        if   ( PIND & (1<<PD2))
        {
               PORTD |=(1<<PD4);
               bRxByte |=0x80;
        }
        else
        {
              PORTD &= ~(1<<PD4);
         }
}
if  (bRxFlag & RX_M_DATA)
{
        bRxFlag &= ~RX_M_DATA;
        send_one_byte(bRxCount + 0x30);
}


  }

Receive-Routine inner Timer-ISR:

	if (bRxFlag & RX_M_RECEIVE)		//	 receive ?
	{
          if (bRxCount & 0x08)		// is this the stop-Bit (9th)
          {
              //bRxFlag &= ~RX_M_RECEIVE;   // receiving sequence done
	      //bRxFlag |= RX_M_DATA;	// signal data
	      GICR |= 1<<INT0;  // re-enable int0 for next

	    }
	    else
            {
              bRxByte >>= 1;	  // Shift right data
              bRxCount++;

/*	    if(PIND&(1<<PD2))   //set bit or leave it
            {
              bRxByte |=0x80;			
	      bRxCount++;

            } */

	  }
	}

und INT0

  if(!(bRxFlag & RX_M_RECEIVE))
  {
  GICR = 0;                     // Disable external interrupt
//  bTxFlag &= ~TX_M_SEND;        // Deactivate Transmit-Mode
  TCNT0 = INT0_PRELOAD;         // Set timer reload-value (to 1.5 bit len). 29 = time delay that
			        // have already been used in this
			        // interrupt plus the time
			        // that will be used by the time
			        // delay between timer interrupt request
			        // and the actual sampling of the first
			        // data bit.

  TIFR |= (1<<TOV0);            // clear T/C0 overflow flag

  TIMSK |= (1<<TOIE0);          // enable T/C0 overflow interrupt
  bRxCount = 0;                 // Clear Receive Counter
  bOld = 0;
  bCnt = 0;
  bRxFlag |= RX_M_RECEIVE;      // Activate Receive-Mode
  }

so wie ichs jetzt hab kommen nur U's (UUUUUUUU usw.)