#define DDRB (*(volatile unsigned char *)(0x17 + 0x20)) /* Registrador de direção dos dados da porta B*/
#define PORTB (*(volatile unsigned char *)(0x18 + 0x20))/* Registrador de dados */ 
#define IRQ7 __vector_7
#define SIGNAL __attribute__ ((signal))
#define GIMSK (*(volatile unsigned char *)(0x3B + 0x20))
#define SREG (*(volatile unsigned char *) (0x3F + 0x20))
#define TIMSK (*(volatile unsigned char *) (0x39 + 0x20))
#define TCCR0 (*(volatile unsigned char *) (0x33 + 0x20))

static int count;

void IRQ7 (void) SIGNAL;

void IRQ7 (void)
{
  count--;
  if(count == 0)
  {
    PORTB = ~PORTB;
    count = 200;
  }
}

int main (void) { 
  GIMSK = 0xC0;
  SREG = 0x80;
  TIMSK = 0x02;
  TCCR0 = 0X05;
  count = 200;
  DDRB = 0xff; 
  
  PORTB = 0xff;
  
  while (1);
  return 0;
}