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at91_sdcard源码分析(2)

2014-03-11 22:37 239 查看
初始化操作。

//------------------------------------------------------------------------------
/// Initializes a MCI driver instance and the underlying peripheral.
/// \param pMci  Pointer to a MCI driver instance.
/// \param pMciHw  Pointer to a MCI peripheral.
/// \param mciId  MCI peripheral identifier.
/// \param mode  Slot and type of connected card.
//------------------------------------------------------------------------------
void MCI_Init(
    Mci *pMci,
    AT91S_MCI *pMciHw,     //AT91C_BASE_MCI
    unsigned char mciId,   //AT91C_ID_MCI
    unsigned int mode)     //MCI_SD_SLOTB
{
    unsigned short clkDiv;

    SANITY_CHECK(pMci);
    SANITY_CHECK(pMciHw);
    SANITY_CHECK((mode == MCI_MMC_SLOTA) || (mode == MCI_MMC_SLOTB)
                 || (mode == MCI_SD_SLOTA) || (mode == MCI_SD_SLOTB));

    // Initialize the MCI driver structure
    pMci->pMciHw = pMciHw;
    pMci->mciId  = mciId;
    pMci->semaphore = 1;    //初始化信号量
    pMci->pCommand = 0;

    // Enable the MCI clock
    WRITE_PMC(AT91C_BASE_PMC, PMC_PCER, (1 << mciId));

     // Reset the MCI
    WRITE_MCI(pMciHw, MCI_CR, AT91C_MCI_SWRST);

    // Disable the MCI
    WRITE_MCI(pMciHw, MCI_CR, AT91C_MCI_MCIDIS | AT91C_MCI_PWSDIS);

    // Disable all the interrupts
    WRITE_MCI(pMciHw, MCI_IDR, 0xFFFFFFFF);

    // Set the Data Timeout Register
    WRITE_MCI(pMciHw, MCI_DTOR, DTOR_1MEGA_CYCLES);

    // Set the Mode Register: 400KHz for MCK = 48MHz (CLKDIV = 58)   //设置MCI的频率是400KHz.
    clkDiv = (BOARD_MCK / (400000 * 2)) - 1;
    WRITE_MCI(pMciHw, MCI_MR, (clkDiv | (AT91C_MCI_PWSDIV & (0x7 << 8))));

    // Set the SDCard Register
    WRITE_MCI(pMciHw, MCI_SDCR, mode);

    // Enable the MCI and the Power Saving
    WRITE_MCI(pMciHw, MCI_CR, AT91C_MCI_MCIEN);

    // Disable the MCI peripheral clock.
    WRITE_PMC(AT91C_BASE_PMC, PMC_PCDR, (1 << mciId));
}
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