28377D的ADC16位采样问题

EALLOW;

AdcaRegs.ADCCTL2.bit.PRESCALE = 6; //set ADCCLK divider to /4

AdcSetMode(ADC_ADCA, ADC_RESOLUTION_16BIT, ADC_SIGNALMODE_DIFFERENTIAL);//write configurations

AdcaRegs.ADCCTL1.bit.INTPULSEPOS = 1;//Set pulse positions to late

AdcaRegs.ADCCTL1.bit.ADCPWDNZ = 1;//power up the ADCs

DELAY_US(1000);

//ADCIN1P&ADCIN1N
AdcaRegs.ADCSOC0CTL.bit.CHSEL = 0; //SOC0 will convert pin A0&A1
AdcaRegs.ADCSOC0CTL.bit.ACQPS = 63; //sample window is acqps +
                                                                              //1 SYSCLK cycles
                                                                              //320ns
//ADCIN2P&ADCIN2N
AdcaRegs.ADCSOC1CTL.bit.CHSEL = 2; //SOC1 will convert pin A2&A3
AdcaRegs.ADCSOC1CTL.bit.ACQPS = 63; //sample window is acqps +
                                                                              //1 SYSCLK cycles
                                                                              //320ns
//ADCIN3P&ADCIN3N
AdcaRegs.ADCSOC2CTL.bit.CHSEL = 4; //SOC2 will convert pin A4&A5
AdcaRegs.ADCSOC2CTL.bit.ACQPS = 63; //sample window is acqps +
                                                                              //1 SYSCLK cycles
                                                                              //320ns
//ADCIN4P&ADCIN4N
AdcaRegs.ADCSOC3CTL.bit.CHSEL = 14; //SOC3 will convert pin A14&A15
AdcaRegs.ADCSOC3CTL.bit.ACQPS = 63; //sample window is acqps +
                                                                              //1 SYSCLK cycles
                                                                              //320ns

AdcaRegs.ADCINTSEL1N2.bit.INT1SEL = 3; //end of SOC1 will set INT1 flag
AdcaRegs.ADCINTSEL1N2.bit.INT1E = 1; //enable INT1 flag
AdcaRegs.ADCINTFLGCLR.bit.ADCINT1 = 1; //make sure INT1 flag is cleared

EDIS;

以上为配置函数，以下为main主循环函数

//start conversions immediately via software, ADCA

 AdcaRegs.ADCSOCFRC1.all = 0x000F; //SOC0 ~ SOC3

//wait for ADCA to complete, then acknowledge flag

while(AdcaRegs.ADCINTFLG.bit.ADCINT1 == 0);
AdcaRegs.ADCINTFLGCLR.bit.ADCINT1 = 1;

//store results

AdcaResult0 = AdcaResultRegs.ADCRESULT0;
AdcaResult1 = AdcaResultRegs.ADCRESULT1;
AdcaResult2 = AdcaResultRegs.ADCRESULT2;
AdcaResult3 = AdcaResultRegs.ADCRESULT3;

读出来的数据和以上所说的问题一样，请问这个3V / 65536 * (34096-32768) = 60mV的误差是因为我程序配置的问题吗？我在硬件管脚上量查分电压为4mV