atmega8 usart rx spinnt

#include <avr/io.h>

#include <avr/interrupt.h>

#define F_CPU 12000000

#include <util/delay.h>

#define BAUD 9600

#define UBRR_VAL F_CPU/16/BAUD-1

void delay_ms(int delay) {

        int i;

        for (i=0;i<=delay;i++) {

                _delay_ms(1);

        }

}

void init_uart(unsigned int ubrr) {

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

        UBRRL = (unsigned char)(ubrr);

        UCSRB |= (1<<RXEN);

        UCSRB |= (1<<TXEN);

        UCSRB |= (1<<RXCIE);

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

}

void send_char(unsigned char data) {

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

        UDR = data;

}

void send_string(char *data) {

        while (*data) {

                send_char(*data);

                data++;

        }

}

ISR(USART_RXC_vect) {

        send_string("Interrrupt!!!");

}

int main(void) {

        init_uart(UBRR_VAL);

        DDRC |= (1<<PC5);

        sei();

        while (1) {

                PORTC &= (!(1<<PC5));

                delay_ms(1000);

                send_string("Hallo");

                send_char(0x0A);

                PORTC |= (1<<PC5);

                delay_ms(1000);

        }

        return 1;

}