Multiplexing 7 segment LED display

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#include <avr/io.h>
#include <avr/interrupt.h>
 
#define Data_Comm PINB0 //pin14
 
#define LED1 PINB6 //NPN led disp. 1 pin9
#define LED2 PINB7 //NPN led disp. 2 pin10
 
#define bitA PIND0 //pin 25, LSbit for 4511
#define bitB PIND1
#define bitC PIND2
#define bitD PIND3
 
#define BCD PORTD
#define MUX PORTB
 
//ATmega 8, 1 MHz
 
volatile unsigned int g_rez = 0, g_isp = 0, g_a = 0;
volatile unsigned char g_z = 1, g_rac=1, g_zn0, g_zn1;
 
unsigned int ADC_rez(void);
void ADC_ini(void);
 
int main( void )
{       
    
    DDRB |= 1<<LED1 | 1<<LED2;
    DDRC |= 1<<bitA | 1<<bitB | 1<<bitC | 1<<bitD;
    MUX &= ~(1<<LED1) & ~(1<<LED2);//NPN turn off (MOSFET gate PULL-UP )
    
    ADC_ini();
    
    sei();
    
    g_isp = ADC_rez()>>1;//ADC result need to divide by 2
 
    OCR1A = 3906; 
    TIMSK |= 1<<OCIE1A; 
    TCCR1B|=(1<<WGM12) | (1<<CS12); //timer1 CTC mode
    
    OCR2 = 130;//Output compare register
    TCCR2 |= 1<<WGM21 | 1<<CS22;//prescaler 8bit timer 2 /64    
    TIMSK |= 1<<OCIE2;
    
    while(1){       
        
        if(ADCSRA & 1<<ADIF){ 
            g_rez = ADC_rez()>>1; 
            ADCSRA |= 1<<ADIF; 
            ADCSRA |= 1<<ADSC;
            }
    
    }
    
    
    
    
    
}
 
ISR (TIMER1_COMPA_vect)
{   
    g_a++;
    if(g_a==10)
    {
        g_isp=g_rez;
        g_rac=1;//flag for new value
        g_a=0;
    }
}
 
ISR (TIMER2_COMP_vect)
{
    unsigned char pr=0, dr=0;
    
    if(g_z)
    {
        if(g_rac)//if new value is ready
        {
            pr=g_isp/10;
            dr=g_isp-pr*10;
            g_zn0 = pr;//save first number
            g_zn1 = dr;//save second number
            g_rac=0;
        }
        pr = g_zn0;
        
        MUX &= ~(1<<LED2);//turn off LED disp. 2(right)
        BCD &= ~(0x0F);
        BCD |= pr; 
        MUX |= 1<<LED1;
        g_z=0;
    }
    else
    {   
        dr = g_zn1;
        
        MUX &= ~(1<<LED1);//turn off LED disp. 1(left)
        BCD &= ~(0x0F);
        BCD |= dr; //ispisujem drugu znamenku
        MUX |= 1<<LED2;
        g_z=1;
        
    }
}
 
unsigned int ADC_rez(void){
    unsigned int MSBy, LSBy;
    LSBy= ADCL; // low byte
    MSBy= ADCH; // high byte of 10 bit ADC register
    MSBy= MSBy<<8;
    MSBy |= LSBy; 
    
    return MSBy;
 
}
void ADC_ini(void){
    ADMUX |= 1<<REFS0;
    ADCSRA |= 1<<ADEN | 1<<ADPS1 | 1<<ADPS0; //enable ADC, prescaler: /8
    ADCSRA |= 1<<ADSC; //start conv.
    while(ADCSRA & 1<<ADSC){}
    while(!(ADCSRA & 1<<ADIF)){}
}