Error in using multiple channel ADC in AVR ATMEGA8

[habibparacha]

I am trying to use multiple channels of ADC using interrupts but whenever the I run the simulation in proteus it gives the error.

Only the first conversion is written to the ADCL register and the next conversion is not written to it. It gives the error .

Below is my code and the picture of error I get
Kindly Help,

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Code C - [expand]
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#include <avr/io.h>
#include <inttypes.h>
#include <avr/interrupt.h>
#include <util/delay.h>
#include <avr/sleep.h>
 
#define NUMCHANNELS 2
 
volatile uint8_t CurrentCh;
volatile uint8_t Channel;
 
ISR(ADC_vect)
{   
    PORTD= ADCL;
    
    Channel++;
    CurrentCh = Channel & 0b00000111;
    
     if(Channel<NUMCHANNELS)
     { 
        ADMUX |= CurrentCh;
        PORTB= 0xff;
     }       
     else
     { 
        Channel=0;
        ADMUX |= CurrentCh;
        PORTB= 0x00;     
     }       
    
    ADCSRA|= (1<<ADSC);
    
     //PORTD= ADCL;
     //PORTB= 0xff;
    
}   
 
int main(void)
{
    DDRC=0x00; //initilize as input
    DDRB=0xff;
    DDRD=0xff;
    PORTB=0X00;
    PORTD=0X00;
    Channel = 0;
    CurrentCh = Channel & 0b00000111;
    
    //** Setting Sleep mode idle **//
    //MCUCR |= (1<<SE);
    //MCUCR &= !((1 << SM0) | (1 << SM1) | (1 << SM2));
    
    ADMUX|=(1<<REFS0);
    //ADMUX |= (1 << MUX0) | (1<<MUX1);//| (1 << MUX2) | (1 << MUX3) );
    ADMUX |= CurrentCh;
    
    //Prescaler = 64, free running mode = off, interrupts off.
    ADCSRA |= (1 << ADPS2) | (1 << ADPS1);
    //ADCSRA |= (1 << ADIF);    //Reset any pending ADC interrupts
    
    ADCSRA |= (1 << ADEN) | (1 << ADIE);  //Enable the ADC
    sei();
    ADCSRA|= (1<<ADSC);
    
    //ADCSRA|=(1<<ADIF);    
    
    //sei();
    while(1)
    {SLEEP_MODE_IDLE;
    }
}

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[alexan_e]

The problem is PORTD= ADCL;

If you check the datasheet it says

When ADCL is read, the ADC Data Register is not updated until ADCH is read. Consequently, if the result is left adjusted and no more than 8-bit precision is required, it is sufficient to read ADCH.
Otherwise, ADCL must be read first, then ADCH.

So you must either read ADCH too or replace the above line with PORTD= ((0xff) & ADCW) or left adjust the result and read ADCH