#include <avr/io.h>    

void delay100ms(void);			

int main(void) 
{
	
	DDRB = 0xFF;    	
	while (1) 
	{
		PORTB = 0xAA;
		delay100ms();
		PORTB = 0x55;
		delay100ms();	
	} 
	return 0;
}


void delay100ms(void){
	
	unsigned int i ;
	for(i=0; i<42150; i++);
}