#define PORTA_DDR*(volatile uint8_t *)0X21
#define PORTA_DATA*(volatile uint8_t *)0X22

#define PORTB_DDR*(volatile uint8_t *)0X24
#define PORTB_DATA*(volatile uint8_t *)0X25

int main(){
  PORTA_DDR=0XFF;
  PORTB_DDR=0XFF;
  volatile long i;
  while(1){
    PORTA_DATA=0XFF;
    for(i=0;i<400000;i++){}
    PORTA_DATA=0X00;
    PORTB_DATA=0XFF;
    for(i=0;i<400000;i++){}
    PORTB_DATA=0X00;
  }
}