at91_sdcard源码分析(2)

最新推荐文章于 2021-08-18 22:37:38 发布

xgbing

最新推荐文章于 2021-08-18 22:37:38 发布

阅读量1.2k

点赞数

CC 4.0 BY-SA版权

分类专栏： [SD/MMC] 深入浅出SD卡

本文链接：https://blog.youkuaiyun.com/xgbing/article/details/21030321

[SD/MMC] 同时被 2 个专栏收录

20 篇文章

订阅专栏

深入浅出SD卡

19 篇文章

订阅专栏

本文介绍了一个用于初始化 MCI (多媒体控制接口) 驱动实例及其底层外设的过程。该过程包括配置时钟、复位 MCI、设置工作模式等步骤，确保 MCI 外设能够正确地与 MMC 或 SD 卡进行通信。

摘要生成于 C知道，由 DeepSeek-R1 满血版支持，前往体验 >

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));
}