#define F_CPU 8000000UL
#include<avr/io.h>
#include<util/delay.h>

int main()
	{
	DDRB=0xff;   // set as output port
	while(1)
		{
		PORTB=0xff;
		_delay_ms(1000);
		PORTB=0x00;
		_delay_ms(1000);
		}
    return 0;
	}