UART überträgt nach Interrupt=enable nichts mehr

/*

 * test_loeschen.c

 *

 * Created: 11.09.2019 22:29:37

 *

 */ 

#define F_CPU 1000000UL

#include <avr/io.h>

#include <avr/interrupt.h>

#include <util/delay.h>

void uart_putc( unsigned char data )

{

  while ( !( UCSRA & (1<<UDRE)) )

  ;

  UDR = data;

}

int main(void)

{

  #define BAUD 9600

  unsigned int ubbr =  F_CPU/8/BAUD-1; 

  UBRRH = (unsigned char)(ubbr>>8);

  UBRRL = (unsigned char)ubbr;

  UCSRB |= (1<<RXEN)|(1<<TXEN);

  UCSRB |= (1<<RXCIE);

  UCSRC = (1<<URSEL)|(1<<USBS)|(3<<UCSZ0);

  UCSRA |= (1<<U2X);

  sei();

    /* Replace with your application code */

    while (1) 

    {

    uart_putc(5);      

    }

}