基于51单片机的SD卡读卡器MMC存储器 proteus仿真程序设计

硬件设计

链接：
提取码：4ebs

程序设计

#include <reg52.H>

#define F_OSC  11059200//晶振平率Hz
#define F_BAUD 9600
#define RELOAD 256-F_OSC/12/32/F_BAUD
#define CR 0x0D        //回车

//定义SD卡需要的4根信号线
sbit SD_CLK = P1^4;
sbit SD_DI  = P1^6;
sbit SD_DO  = P1^5;
sbit SD_CS  = P1^7;

unsigned char xdata DATA[512];
//定义512字节缓冲区，注意需要使用 xdata关键字


//===========================================================
//写一字节到SD卡,模拟SPI总线方式
void SdWrite(unsigned char n)
{

    unsigned char i;
    
    for(i=8;i;i--)
    {
        SD_CLK=0;
        SD_DI=(n&0x80);
        n<<=1;
        SD_CLK=1;
        }
        SD_DI=1; 
    } 
//===========================================================
//从SD卡读一字节,模拟SPI总线方式
unsigned char SdRead()
{
    unsigned char n,i;
    for(i=8;i;i--)
    {
        SD_CLK=0;
        SD_CLK=1;
        n<<=1;
        if(SD_DO) n|=1;
    
    }
    return n;
}
//============================================================
//检测SD卡的响应
unsigned char SdResponse()
{
    unsigned char i=0,response;
    
    while(i<=8)
    {
        response = SdRead();
        if(response==0x00)
        break;
        if(response==0x01)
        break;
        i++;
    }
    return response;
} 
//================================================================
//发命令到SD卡
void SdCommand(unsigned char command, unsigned long argument, unsigned char CRC)
{

    SdWrite(command|0x40);
    SdWrite(((unsigned char *)&argument)[0]);
    SdWrite(((unsigned char *)&argument)[1]);
    SdWrite(((unsigned char *)&argument)[2]);
    SdWrite(((unsigned char *)&argument)[3]);
    SdWrite(CRC);
}
//================================================================
//初始化SD卡
unsigned char SdInit(void)
{
    int delay=0, trials=0;
    unsigned char i;
    unsigned char response=0x01;
    
    SD_CS=1;
    for(i=0;i<=9;i++)
    SdWrite(0xff);
    SD_CS=0;
    
    //Send Command 0 to put MMC in SPI mode
    SdCommand(0x00,0,0x95);
    
    
    response=SdResponse();
    
    if(response!=0x01)
    {
        return 0;
    } 

    while(response==0x01)
    {
        SD_CS=1;
        SdWrite(0xff);
        SD_CS=0;
        SdCommand(0x01,0x00ffc000,0xff);
        response=SdResponse();
    } 

    SD_CS=1;
    SdWrite(0xff);
    return 1; 
}
//================================================================
//往SD卡指定地址写数据,一次最多512字节
unsigned char SdWriteBlock(unsigned char *Block, unsigned long address,int len)
{
    unsigned int count;
    unsigned char dataResp;
    //Block size is 512 bytes exactly
    //First Lower SS
    
    SD_CS=0;
    //Then send write command
    SdCommand(0x18,address,0xff);
    
    if(SdResponse()==00)
    {
        SdWrite(0xff);
        SdWrite(0xff);
        SdWrite(0xff);
        //command was a success - now send data
        //start with DATA TOKEN = 0xFE
        SdWrite(0xfe);
        //now send data
        for(count=0;count<len;count++) SdWrite(*Block++);
        
        for(;count<512;count++) SdWrite(0);
        //data block sent - now send checksum
        SdWrite(0xff); //两字节CRC校验, 为0XFFFF 表示不考虑CRC
        SdWrite(0xff);
        //Now read in the DATA RESPONSE token
        dataResp=SdRead();
        //Following the DATA RESPONSE token
        //are a number of BUSY bytes
        //a zero byte indicates the MMC is busy
        
        while(SdRead()==0);
        
        dataResp=dataResp&0x0f; //mask the high byte of the DATA RESPONSE token
        SD_CS=1;
        SdWrite(0xff);
        if(dataResp==0x0b)
        {
        //printf("DATA WAS NOT ACCEPTED BY CARD -- CRC ERROR\n");
        return 0;
        }
        if(dataResp==0x05)
        return 1;
        
        //printf("Invalid data Response token.\n");
        return 0;
    }
    //printf("Command 0x18 (Write) was not received by the MMC.\n");
    return 0;
}

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文件仅供参考

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