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eMMC and SD card on same controller

Tobyn VanVeghten
Intellectual 700 points

Hey,

Could someone clarify something for me please?  In reading the documentation for the C6748 MMC/SD card controller, it sounds like I can have one SD and an eMMC connected to the same controller (e.g. MMCSD0).  Is this the case?  Or do I need to connect the eMMC to one (MMCSD0) and the SD card to the other (MMCSD1)?

Thanks,

Tobyn

  • 0
    TI__Guru* 83855 points

    Tobyn

    The C6478 device supports 2 instances MMC/SD controllers, you can use either one to interface MMC (or eMMC) or SD or SDIO based on pinmux/layout considerations.

    Keep in mind that the MMC/SD controller on the device is MMCv4.0 compliant.

    Regards

    Mukul

  • 0 in reply to Mukul Bhatnagar
    Intellectual 700 points

    By instance, are you referring to what the data sheet calls MMCSD0 and MMCSD1?  So, one set of pins for MMCSD0 and a separate set of pins for MMCSD1?

    Thanks,

    Tobyn

  • 0
    Guru 26430 points

    I vaguely remember that the SD and MMC specs allowed multiple cards to be connected to one bus or set of lines. At the HW level, this was done in much the same way as I2C, via open collector lines. You might have noticed that the IO lines always need pullups. That said, I've never seen or heard of anybody attaching more than one card of the same kind to a controller. Never mind a mix of MMC and SD types to the same controller. A bit of a note at http://en.wikipedia.org/wiki/SD_Card. See section on "Ganging cards together". No idea if the C6748 SD card controller actually supports multiple cards. Most firmware drivers I've seen don't.

  • 0 in reply to Norman Wong
    Intellectual 700 points

    I was originally thinking the eMMC and SD card had to be on peripheral ports, but combining them into one simplifies my life.  I was hoping to make the SD card a backup bootable device, but the 2nd MMC/SD port does not support booting.  Oh well.  I will just put a billion zero ohm resistors on the board to reconfigure it if needed later.

    Thanks,

    Tobyn