MSP-EXP430FR2355: issue with ADC at 24Mhz clock

Part Number: MSP-EXP430FR2355

Hello Team,

I'm working on ADC, i want to read data from 3 channels A1,A2,A3 and initially ADC is by default to MODOSC getting data for 3 channels fine.

But when I configured ADC to 24Mhz with the ref(slau445i) UG, Only one channel(A1) data is repeating every time. why it is not getting updated ?

like if A1 = 768 , A2 and A3 also getting 768. ADC_channelno is increasing but A2 and A3 not updating, why? below is the code i've tried. Any help would be greatly thankful.

 while (ADC_channelno <= 3)
    {

        // ADC conversion enable
        while ((ADCCTL1 & ADCBUSY)); //Wait for conversion to end
        ADCCTL0 &= ~ADCENC;     // Disable
        ADCMCTL0 = (ADCMCTL0 & ~ADCINCH) | ADC_channelno; // We "know" INCH is the LSb-s
        ADCCTL0 |= ADCENC | ADCSC; // // Sampling and conversion start(Every Channel)
        while ((ADCCTL1 & ADCBUSY)); //Wait for conversion to end
        __bis_SR_register(GIE); // LPM0, ADC_ISR will force exit

        sprintf(str, "%d", ADC_Result1);
        for(i=0; str[i] != '\0'; i++)
                {
                  temp = str[i];
                  str1[j] += temp;
                  j++;
                }
    }
    if (ADC_channelno > 3)
    {
        ADC_channelno = 1;
    }

void adc_init()
 {
     // Configure ADC A1,A2,A3 pin
        P1SEL0 |= BIT1;
        P1SEL1 |= BIT1;

        P1SEL0 |= BIT2;
        P1SEL1 |= BIT2;

        P1SEL0 |= BIT3;
        P1SEL1 |= BIT3;

     // Configure ADC12
        ADCCTL0 |= ADCSHT_2 | ADCON;                             // ADCON, S&H=16 ADC clks
        ADCCTL1 |= ADCSSEL_3 | ADCSHP | ADCSHS_0;                // ADCCLK = SMCLK; sampling timer
        ADCCTL2 &= ~ADCRES;                                      // clear ADCRES in ADCCTL
        ADCCTL2 |= ADCRES_2;                                     // 12-bit conversion results
        ADCIE |= ADCIE0;                                         // Enable ADC conv complete interrupt
}

// ADC interrupt service routine
#if defined(__TI_COMPILER_VERSION__) || defined(__IAR_SYSTEMS_ICC__)
#pragma vector=ADC_VECTOR
__interrupt void ADC_ISR(void)
#elif defined(__GNUC__)
void __attribute__ ((interrupt(ADC_VECTOR))) ADC_ISR (void)
#else
#error Compiler not supported!
#endif
{
    switch (__even_in_range(ADCIV, ADCIV_ADCIFG))
    {
    case ADCIV_NONE:
        break;
    case ADCIV_ADCOVIFG:
        break;
    case ADCIV_ADCTOVIFG:
        break;
    case ADCIV_ADCHIIFG:
        break;
    case ADCIV_ADCLOIFG:
        break;
    case ADCIV_ADCINIFG:
        break;
    case ADCIV_ADCIFG:
        ADCIFG &= ~ADCIFG;              // clear interrupt flag
        ADC_Result1 = ADCMEM0;         // Save away result
        ADC_channelno++;
        break;
    default:
        break;
    }
}