/* I/O PORT B, DATA DIRECTION REGISTER (0 -> in, 1 -> out) */
#define DDRB    (*(volatile unsigned char *)(0x17 + 0x20))
/*#define DDRB    (*(volatile unsigned char *)(0x04 + 0x20))*/ /*for ATMEGA328p*/

/* I/O PORT B, DATA REGISTER */
#define PORTB   (*(volatile unsigned char *)(0x18 + 0x20))
/*#define PORTB	(*(volatile unsigned char *)(0x05 + 0x20))*/ /*for ATMEGA328p*/

void delay()
{
    unsigned int count = 0xffff;
    asm volatile ("1:	sbiw %0,1	\n"
		  "	brne 1b		\n" : "=w"(count) : "0"(count));
}

int main(void) {

    /* Set the whole port (all bits) to "output" */
    DDRB = 0xff;

    while(1) {
        /* Turn on all leds connected to port B */
        PORTB = 0x00; 

        /* Delay */
        delay();

        /* Turn off all leds connected to port B */
        PORTB = 0xff;

    	/* Delay */
        delay();
    }

    return 0;
}