MSP430f5310 ADC多通道采集问题

工程师：

            你好，我在使用ADC多通道采集时遇到的问题，首先，我使用的ADC 4通道10位采集（A3，A2，A1,A0），采用内部基准电压2.5v，利用DMA取出ADC转换数据。我的问题是，在A3电压为0时，为什么采集的AD转换值 为110.理论上应该是0，才对，不知道问题出在什么地方，请给出帮助。谢谢

//******************************************************************************
#include <msp430.h>

unsigned int ADC_Result[4];              

int main(void)
{
  WDTCTL = WDTPW | WDTHOLD;                 // Stop WDT

  // Configure ADC10
  ADC10CTL0 = ADC10SHT_2 | ADC10MSC | ADC10ON;// 16ADCclks, MSC, ADC ON
  ADC10CTL1 = ADC10SHP | ADC10CONSEQ_1;     // sampling timer, s/w trig.,single sequence
  ADC10CTL2 |= ADC10RES;                   // 10-bit resolution
  ADC10MCTL0 = ADC10SREF_1 |ADC10INCH_3;                 // A0,A1,A2，A3(EoS), AVCC reference
 
  while(REFCTL0 & REFGENBUSY);              // If ref generator busy, WAIT                                         
  REFCTL0 |= REFVSEL_2|REFON;               // Select internal ref = 2.5V
 
  // Configure DMA0 (ADC10IFG trigger)
  DMACTL0 = DMA0TSEL_24;                    // ADC10IFG trigger
  __data16_write_addr((unsigned short) &DMA0SA,(unsigned long) &ADC10MEM0);
                                            // Source single address 
  __data16_write_addr((unsigned short) &DMA0DA,(unsigned long) &ADC_Result[0]);
                                            // Destination array address 
  DMA0SZ = 0x04;                            // 4 conversions
  DMA0CTL = DMADT_4 | DMADSTINCR_3  | DMAEN | DMAIE;
                                            // Rpt, inc dest, byte access,
                                            // enable int after seq of convs  
  while(1)
  {
    while (ADC10CTL1 & ADC10BUSY);          // Wait if ADC10 core is active
    ADC10CTL0 |= ADC10ENC | ADC10SC;        // Sampling and conversion start
    __bis_SR_register(CPUOFF | GIE);        // LPM0, ADC10_ISR will force exit
    __delay_cycles(5000);                   // Delay between sequence convs   
    __no_operation();                       // BREAKPOINT; check ADC_Result
  }
}

#pragma vector=DMA_VECTOR
__interrupt void DMA0_ISR (void)

{
  switch(__even_in_range(DMAIV,16))
  {
    case  0: break;                         // No interrupt
    case  2:
      // sequence of conversions complete
      __bic_SR_register_on_exit(CPUOFF);    // exit LPM
      break;                                // DMA0IFG
    case  4: break;                         // DMA1IFG
    case  6: break;                         // DMA2IFG
    case  8: break;                         // Reserved
    case 10: break;                         // Reserved
    case 12: break;                         // Reserved
    case 14: break;                         // Reserved
    case 16: break;                         // Reserved
    default: break;
  }  
}