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DM816x Circuit

Junqing Zhao
Intellectual 770 points

Hi，all

         when I see the evm8168 Circuit schematics which spectrum digital provided. In page 35 ，it is about SD interface. I find U66 is FDC6631L，it work like a switch。

The MMC_POW provide power for SD Card。When I plug the SD card ，it should  be high level。Is it correct？

        When I Used  the oscilloscope observing MMC_POW signal，I find it could be a short time low level.Is it correct?

      If the MMC_POW  is always high level,   I can remove the U66 .

Looking    forward your reply.

Thanks

               Zhao

  • 0
    TI__Guru**** 393215 points
    Hi Zhao,
     
    Yes, you can design the SD card connector with constant 3.3V supply. However, in this case it's recommendable to change SD cards only when board power is switched off.
  • 0 in reply to Biser Gatchev-XID
    Intellectual 770 points

    Thanks.

    However，i obversed the MMC_POW is a short time low level when i use mmcinfo commond after I load the SD uboot first stage。And the mmcinfo is as follow：

    TI8168_EVM#mmcinfo
    Card did not respond to voltage select!
    Device: OMAP SD/MMC
    Manufacturer ID: 0
    OEM: 0
    Name: Tran Speed: 0
    Rd Block Len: 0
    MMC version 0.0
    High Capacity: No
    Capacity: 0
    Bus Width: 1-bit

    The first stage MLO file，I load it with CCS5 because it did not autoboot when power on。

    The low level and the MMC info seems to be the card is not exist，but I have plug with a 2G SD card which contain SD U-boot files。

    Thanks for your reply.

                Zhao

  • 0 in reply to Junqing Zhao
    TI__Guru**** 170625 points

    Hello Zhao,

    The MMC_POW (referenced as SD_POW in the DM816x TRM and Datasheet) is used for MMC/SD card on/off power supply control. When high, denotes power-on
    condition.

    For how to control the SD_POW pin, check here:

    http://e2e.ti.com/support/dsp/davinci_digital_media_processors/f/716/p/165467/604466.aspx

    The MMCHS_SYSTEST register in DM814x correspond to the SD_SYSTEST register in DM816x.

    Regards,

    Pavel