//connect 8 leds to port f and blink them form 3 to 0

#include <stdint.h>

#define DDRF  (*(volatile uint8_t*)0x30)
#define PORTF (*(volatile uint8_t*)0x31)

void delay1sec(void){
    TCNT1  = 0;
    TCCR1A = 0x00;
    TCCR1B = 0x05;          

    while (TCNT1 < 15625);

    TCCR1B = 0x00;          
}

void setup() {
    DDRF |= (1<<4) | (1<<5) | (1<<6) | (1<<7);   
}

void loop() {
    for (int8_t i = 7; i >= 4; i--) {
        PORTF = (1 << i);   
        delay1sec();
        PORTF = 0x00;       
        delay1sec();
    }
}