MPLAB X IDE v2.05 +CX8 Pro PIC12F1501的AD问题

#include <xc.h> // include standard header file

// set Config bits

#pragma config CP = OFF, FOSC = INTOSC     // Code Protection bit (Code protection off).

#pragma config MCLRE = OFF                           

#pragma config WDTE = OFF                           //Watch dog timer off

// Definitions

#define _XTAL_FREQ  4000000       //this is used by the __delay_ms(xx) and __delay_us(xx) functions

//**********************************************************************************

void init( )

{

    // PORT A Assignments

    TRISAbits.TRISA0 = 1;                                        //RA0 = Analog Voltage In

    TRISAbits.TRISA1 = 1;                                        //RA1 = input

    IOCANbits.IOCAN1 = 1;                                        //RA1 NEGATIVE EDGE REGISTER IOC

    TRISAbits.TRISA2 = 0;                                        //RA2 = output

    TRISAbits.TRISA3 = 0;                                        //RA3 = nc (MCLR)

    TRISAbits.TRISA4 = 0;                                        //RA4 = output

    TRISAbits.TRISA5 = 0;                                        //RA5 = output

    // set up oscillator control register.

    OSCCONbits.IRCF = 0x0D;             //set OSCCON IRCF bits 1101 frequency=4Mhz

    OSCCONbits.SCS = 0x02;              //set the SCS bits internal oscillator block

    // set up INTCON register.

    INTCONbits.IOCIE = 1;                      //set INTCON IOCIE bits Enabled 

    // set up FVRCON register.

    //FVRCONbits.FVREN = 1;       //Fixed Voltage Reference Enabled 1.024V

    //FVRCONbits.ADFVR = 0x02;    //ADC FVR Buffer Gain is 2x, 2 x VFVR = 2.048V

    // set up ADC control register.

    ANSELAbits.ANSA0 = 1;                                        //Select A0 as analog input pin

    ADCON0bits.CHS = 0x00;              //Set ADC conversion Channel AN0.

    ADCON0bits.ADON = 1;                                        //ADC is on

    ADCON1bits.ADCS = 0x04;             //Set ADC clock FRC x111. 0x04 = Fosc/4

    ADCON1bits.ADFM = 0x01;             //Set Data Right justified.

    ADCON1bits.ADPREF = 0x00;           //Set Vref connected to VDD.



}

//**********************************************************************************

unsigned int Read_ADC_Value(void)

{

    unsigned int ADCValue;

    __delay_ms(10);

    ADCON0bits.GO = 1;              //start conversion

    while (ADCON0bits.GO)  continue;//wait for conversion to finish

    ADCValue = ADRESH << 8;         //get the 2 msbs of the result and rotate 8 bits to the left

    ADCValue = ADCValue + ADRESL;   //now add the low 8 bits of the resut into our return variable

    return (ADCValue);              //return the 10bit result in a single variable

}

//***********************************************************************************

//***********************************************************************************

void main( )

{

    unsigned int AnalogValue = 0;

    unsigned char i = 0;

    init();

    while(1)

    {

        AnalogValue = Read_ADC_Value();

        __delay_ms(400);

        if(AnalogValue <= 200)

            LATAbits.LATA5 ^= 1;

        else

            LATAbits.LATA5 = 0;

    }

}