przerwania zadanie1

#include<avr/io.h>
#include<avr/interrupt.h>

    volatile int counter;
ISR(TIMER0_OVF_vect){


if(counter == 20){
    counter = 0;
    PORTA = !PORTA;
}

    TCNT0 = 235;
    counter++;

}


int main(void){


    TCCR0 |=  (1<<CS00) | (1<<CS02);
    TIMSK |= (1<<TOIE0);


    TCNT0 = 0;
    DDRA = 0xFF;
    sei();
    PORTA = 235;
    counter = 0;
    while(1){}



}