#define PORTA_DDR  (*(volatile char *)0x21)
#define PORTA_DATA (*(volatile char *)0x22)

#define PORTC_DDR  (*(volatile char *)0x27)
#define PORTC_DATA (*(volatile char *)0x28)
#define PORTC_PIN  (*(volatile char *)0x26)

int main(){
volatile long i;
PORTA_DDR = 0xFF;
PORTC_DDR = 0x00;
PORTC_DATA = 0x01;
while(1)
{
if((PORTC_PIN & 0x01) == 0){
for(i=0; i<400000; i++){
}
if((PORTC_PIN & 0x01) == 0){
PORTA_DATA ^= 0x01;
while((PORTC_PIN & 0x01) == 0){
}
}
}
}
}