#include <avr/io.h>

void nop(int count)
{
        int i;
        for(i = 0; i < count*50; i++)
        {
                  i = i;
        }
}

void port_init(void)
{
        DDRB = 0xff;
        DDRD = 0x00;
        PORTD = 0xff;
}

int main(void)
{
        port_init();
        char b;

        for(;;)
        {
                for(b = 0; b < 6; b++)
                {
                        PORTB = 1<<b;
                        nop(300);
                }
                PORTB = 0;
                for(b = 0; b < 6; b++)
                {
                        PORTD = 1<<b;
                        nop(300);
                }
                PORTD = 0;
        }
}