Atmel Studio 6.2 Simulator ext. Interrupt auslösen?

#include <avr/io.h>

#include <util/delay.h>

#include <avr/interrupt.h>

volatile uint8_t flag=0;        // global variable 

int main(void)

{

  DDRD &= ~(1<<PD2);          // PD2 = Input (INT0)

  DDRB |= (1<<PB1);          // PB1 = Output

  PORTB = 0x00;            // PORTB = low

  EICRA |= (1<<ISC01)|(1<<ISC00);    //The rising edge of INT0 generates an interrupt request

  EIMSK |= (1<<INT0);          //External interrupt request 0 enable

  sei();                // Interrupt enable

  while(1)

  {  

    if(flag == 1)

    {

      _delay_ms(500);

      PORTB &= ~(1 << PB1);       // PB1 = LOW

    }

  }

  return 0;

}

ISR (INT0_vect)              // Begin of ISR 

{

  flag = 1;

  PORTB |= (1 << PB1);        // PB1 = HIGH

}