转载：NIOS2 SD卡 SPI操作函数

unsigned char CS_EN,DI_EN ;
void delay(int i)
{
    while(i>0)
    {
    i--;
    }
}
unsigned char Write_Cmd(unsigned char *cmd,unsigned char lres)
{
    unsigned char rddata[1],time=0;
    do
    {
        time=0;
        IOWR_ALTERA_AVALON_PIO_DATA(CS_EN_BASE,0);
        IOWR_ALTERA_AVALON_PIO_DATA(DI_EN_BASE,0);
        alt_avalon_spi_command(SPI_BASE,0,6,cmd,0,NULL,1);
        IOWR_ALTERA_AVALON_PIO_DATA(DI_EN_BASE,1);
        alt_avalon_spi_command(SPI_BASE,0,1,0xff,0,NULL,1); //provide 8 more clock for internal process of SD card
        do
        {
            alt_avalon_spi_command(SPI_BASE,0,0,NULL,1,rddata,1);
            time++;
        }while((rddata[0]==0xff)&&(time<50));
    }while(rddata[0]==0xff);
    if(!lres)
    IOWR_ALTERA_AVALON_PIO_DATA(CS_EN_BASE,1);
    alt_avalon_spi_command(SPI_BASE,0,1,0Xff,0,NULL,0);    //provide 8 more clock after receive response of SD card
    return(rddata[0]);
}
unsigned char SD_Reset()
{
    unsigned char i ;
    unsigned char rddata[1],wrdata[1];
    unsigned char cmd0[]={0x40,0x00,0x00,0x00,0x00,0x95};
    IOWR_ALTERA_AVALON_PIO_DATA(CS_EN_BASE,1);
    IOWR_ALTERA_AVALON_PIO_DATA(DI_EN_BASE,0);
    for(i=0; i<0x10;i++)
    {
        wrdata[0]=0xff;
        alt_avalon_spi_command(SPI_BASE,0,1,wrdata,0,NULL,0);
    }
    do
    {
        rddata[0]=Write_Cmd(cmd0,0) ;
    }while(rddata[0]!=0x01);
    return 0 ;
}
unsigned char SD_write_sector(unsigned long address,unsigned char *Buffer)
{
    unsigned  char rddata[1],wrdata[1];
    unsigned  int  i;
    unsigned  char cmd24[]={0x58,0x00,0x00,0x00,0x00,0x00,0xff};
    address <<=9;
    cmd24[1]=((address&0xff000000)>>24);
    cmd24[2]=((address&0x00ff0000)>>16);
    cmd24[3]=((address&0x0000ff00)>>8);
    CS_EN =0 ;
    IOWR_ALTERA_AVALON_PIO_DATA(CS_EN_BASE,CS_EN);
    do
    {
        do
        {
          rddata[0]=Write_Cmd(cmd24,1);
        }while(rddata[0]!=0);
        for(i=0;i<5;i++)
        {
            wrdata[0]=0xff;
            alt_avalon_spi_command(SPI_BASE,0,1,wrdata,0,NULL,1);
        }
        DI_EN = 0 ;
        IOWR_ALTERA_AVALON_PIO_DATA(DI_EN_BASE,DI_EN);
        wrdata[0]=0xfe;
        alt_avalon_spi_command(SPI_BASE,0,1,wrdata,0,NULL,1);
        alt_avalon_spi_command(SPI_BASE,0,512,Buffer,0,NULL,1);
        wrdata[0]=0xff;
        alt_avalon_spi_command(SPI_BASE,0,1,wrdata,0,NULL,1); 
        alt_avalon_spi_command(SPI_BASE,0,1,wrdata,0,NULL,1);
        DI_EN=1;
        IOWR_ALTERA_AVALON_PIO_DATA(SPI_BASE,DI_EN);
        alt_avalon_spi_command(SPI_BASE,0,0,NULL,1,rddata,1);
    }while((rddata[0]&0x1f)!=0x05);
    do
    {
        alt_avalon_spi_command(SPI_BASE,0,0,NULL,1,rddata,1);
    }while(rddata[0]!=0xff);
    CS_EN =1 ;
    IOWR_ALTERA_AVALON_PIO_DATA(CS_EN_BASE,CS_EN);
    wrdata[0]=0xff;
    alt_avalon_spi_command(SPI_BASE,0,1,wrdata,0,NULL,0);
    return(0);
}
unsigned char SD_read_sector(unsigned long address,unsigned char *buffer)
{
    unsigned char rddata[1],wrdata[1];
    unsigned char cmd17[]={0x51,0x00,0x00,0x00,0x00,0xff};
    address<<=9;
    cmd17[1]=((address&0xff000000)>>24);
    cmd17[2]=((address&0x00ff0000)>>16);
    cmd17[3]=((address&0x0000ff00)>>8);
    CS_EN = 0;
    IOWR_ALTERA_AVALON_PIO_DATA(CS_EN_BASE,CS_EN);
    do
    {
        rddata[0]=Write_Cmd(cmd17,1);
    }while(rddata[0]!=0);
    do
    {
        alt_avalon_spi_command(SPI_BASE,0,0,NULL,1,rddata,1);
    }while(rddata[0]!=0xfe);
    alt_avalon_spi_command(SPI_BASE,0,0,NULL,512,buffer,1);
    alt_avalon_spi_command(SPI_BASE,0,0,NULL,1,rddata,1);
    alt_avalon_spi_command(SPI_BASE,0,0,NULL,1,rddata,1);
    CS_EN = 1;
    IOWR_ALTERA_AVALON_PIO_DATA(CS_EN_BASE,CS_EN);
    wrdata[0]=0xff;
    alt_avalon_spi_command(SPI_BASE,0,1,wrdata,0,NULL,0);
    return 0;
}
unsigned char SD_Init()
{
    unsigned char rddata_a[1],rddata_b[1],wrdata[1];
    unsigned char time;
    unsigned char cmd55[]={0x77,0x00,0x00,0x00,0x00,0xff};
    unsigned char acmd41[]={0x69,0x00,0x00,0x00,0x00,0xff};
    do
    {
        rddata_a[0]=Write_Cmd(cmd55,0);
        rddata_b[0]=Write_Cmd(acmd41,0);
    }while(rddata_b[0]!=0);
    wrdata[0]=0xff;
    alt_avalon_spi_command(SPI_BASE,0,1,wrdata,0,NULL,0);
    return(0);
}