看书上的程序，一直没有看到有ADC的中断，在AD采样程序中，有对DMA0的中断使能，但是没有对ADC的中断使能。
1、对于AD1CON2的SMPI
这里的中断是什么含义呢？（个人理解，对于有DMA的单片机，是不是只有地址的递增速率这一概念而没有中断了呢？不知道这样对不对）。
2、在DMA0的中断程序执行中（应该是由HALF确定，当数据传输一半或者传输完成产生中断），ADC是否还在采样？程序上只见到ADC的使能置为1，没有看到手动程序关闭ADC，那么是不是就是ADC一直在采样？在DMA0中断程序的时候也执行？还是说DMA0中断的优先级更高，这个时候不响应ADC？
3、AD1CON1的SSRC位，设置为由定时器3比较结束采样并启动转换，这个算是中断吗？相当于定时器的中断？
不知道我能否清楚表达自己的问题，本人小白，刚开始学习PIC单片机，希望大家帮帮忙~~这里附上手册上的采样示例（不同时扫描采样）。
#if defined(__dsPIC33F__)
#include "p33fxxxx.h"
#elif defined(__PIC24H__)
#include "p24hxxxx.h"
#endif
void ProcessADCSamples(unsigned int * AdcBuffer);
/*==========================================================================================
ADC Initialization for Channel Scan
===========================================================================================*/
void initAdc1(void)
{
AD1CON1bits.FORM = 3; // Data Output Format:Signed Fraction (Q15 format)
AD1CON1bits.SSRC = 2; // Sample Clock Source:GP Timer starts conversion
AD1CON1bits.ASAM = 1; // ADC Sample Control:Sampling begins immediately after conversion
AD1CON1bits.AD12B = 0; // 10-bit ADC operation
AD1CON1bits.SIMSAM = 0; // Samples multiple channels individually in sequence
AD1CON2bits.BUFM = 0;
AD1CON2bits.CSCNA = 1; // Scan Input Selections for CH0+ during Sample A bit
AD1CON2bits.CHPS = 0; // Converts CH0
AD1CON3bits.ADRC = 0; // ADC Clock is derived from Systems Clock
AD1CON3bits.ADCS = 63; // ADC Conversion Clock
//AD1CHS0:A/D Input Select Register
AD1CHS0bits.CH0SA = 0; // MUXA +ve input selection (AIN0) for CH0
AD1CHS0bits.CH0NA = 0; // MUXA -ve input selection (Vref-) for CH0
//AD1CHS123:A/D Input Select Register
AD1CHS123bits.CH123SA = 0; // MUXA +ve input selection (AIN0) for CH1
AD1CHS123bits.CH123NA = 0; // MUXA -ve input selection (Vref-) for CH1
//AD1CSSH/AD1CSSL:A/D Input Scan Selection Register
AD1CSSH = 0x0000;
AD1CSSL = 0x000F; // Scan AIN0, AIN1, AIN2, AIN3 inputs
AD1CON1bits.ADDMABM = 0; // DMA buffers are built in scatter/gather mode
AD1CON2bits.SMPI = 3; // 4 ADC buffers
AD1CON4bits.DMABL = 3; // Each buffer contains 8 words
IFS0bits.AD1IF = 0; // Clear the A/D interrupt flag bit
IEC0bits.AD1IE = 0; // Do Not Enable A/D interrupt
AD1CON1bits.ADON = 1; // Turn on the A/D converter
}
/*======================================================================================
Timer 3 is setup to time-out every 125 microseconds (8Khz Rate).As a result, the module
will stop sampling and trigger a conversion on every Timer3 time-out, i.e., Ts=125us.
=======================================================================================*/
void initTmr3()
{
TMR3 = 0x0000;
PR3 = 4999; // Trigger ADC1 every 125usec
IFS0bits.T3IF = 0; // Clear Timer 3 interrupt
IEC0bits.T3IE = 0; // Disable Timer 3 interrupt
T3CONbits.TON = 1; //Start Timer 3
}
// Linker will allocate these buffers from the bottom of DMA RAM.
struct
{
unsigned int Adc1Ch0[8];
unsigned int Adc1Ch1[8];
unsigned int Adc1Ch2[8];
unsigned int Adc1Ch3[8];
} BufferA __attribute__((space(dma)));
struct
{
unsigned int Adc1Ch0[8];
unsigned int Adc1Ch1[8];
unsigned int Adc1Ch2[8];
unsigned int Adc1Ch3[8];
} BufferB __attribute__((space(dma)));;
// DMA0 configuration
// Direction:Read from peripheral address 0-x300 (ADC1BUF0) and write to DMA RAM
// AMODE:Peripheral Indirect Addressing Mode
// MODE:Continuous, Ping-Pong Mode
// IRQ:ADC Interrupt
void initDma0(void)
{
DMA0CONbits.AMODE = 2; // Configure DMA for Peripheral indirect mode
DMA0CONbits.MODE = 2; // Configure DMA for Continuous Ping-Pong mode
DMA0PAD = 0x0300; // Point DMA to ADC1BUF0
DMA0CNT = 31; // 32 DMA request (4 buffers, each with 8 words)
DMA0REQ = 13; // Select ADC1 as DMA Request source
DMA0STA = __builtin_dmaoffset(&BufferA);
DMA0STB = __builtin_dmaoffset(&BufferB);
IFS0bits.DMA0IF = 0; //Clear the DMA interrupt flag bit
IEC0bits.DMA0IE = 1; //Set the DMA interrupt enable bit
DMA0CONbits.CHEN=1; // Enable DMA
}
/*========================================================================================
_DMA0Interrupt():ISR name is chosen from the device linker script.
========================================================================================*/
unsigned int DmaBuffer = 0;
void __attribute__((__interrupt__)) _DMA0Interrupt(void)
{
if(DmaBuffer == 0)
{
ProcessADCSamples(BufferA.Adc1Ch0);
ProcessADCSamples(BufferA.Adc1Ch1);
ProcessADCSamples(BufferA.Adc1Ch2);
ProcessADCSamples(BufferA.Adc1Ch3);
}
else
{
ProcessADCSamples(BufferB.Adc1Ch0);
ProcessADCSamples(BufferB.Adc1Ch1);
ProcessADCSamples(BufferB.Adc1Ch2);
ProcessADCSamples(BufferB.Adc1Ch3);
}
DmaBuffer ^= 1;
IFS0bits.DMA0IF = 0; //Clear the DMA0 Interrupt Flag
}
void ProcessADCSamples(unsigned int * AdcBuffer)
{
/* Do something with ADC Samples */
}
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