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AM6421: Terminal for SD boot

Tsurumoto
Genius 16825 points

Part Number: AM6421

Tool/software:

Hi

Customer will only use the SD card during boot (SDBOOT).

Therefore, UHS-I will not be required, so they only want to supply 3.3V to SD.

 

From the HW perspective, I have a question about terminal processing.

They want to connect VDDA_3P3_SDIO and cap_VDDSHV_MMC1 directly to GND because they only want to provide 3.3V to SD.

Is it appropriate for terminal processing?

 

From the SW point of view, I have a question about terminal processing.

The customer code does not plan to use UHS-I, but they want to use SDBOOT.

When using SDBOOT, is there any code for UHS-I executed in ROM code or SBL, and as a result, it becomes necessary to process the terminal for UHS-I?

  • 0
    TI__Guru** 110030 points

    Hello Tsurumoto-san,

    I am starting by sending your thread to a team member to comment from the ROM code standpoint. Feel free to ping the thread if you do not get a response within a couple of business days.

    Regards,

    Nick

  • 0 in reply to Nick Saulnier
    TI__Genius 16825 points

    Hi Nick

    Were you able to get any responce from ROM code team?

  • +1
    TI__Guru 64655 points

    From a hardware perspective, it is okay to power the MMC1 IO power rail (VDDSHV5) from a fixed 3.3V power supply when you do not plan to use UHS-I SD Cards, or you do not plan to use any of the faster 1.8V signaling data transfer modes supported by UHS-I SD Cards. You must ensure your software never tries to use any of the 1.8V signal modes if you ever attach an UHS-I SD Card. Therefore, your concern with what the ROM code does is valid.  For the proposed connection topology, you need to be sure the SD Card ROM boot code never uses any of the 1.8V signal modes if it detects a UHS-I SD Card.  I will let the ROM code team answer this question.

    VDDA_3P3_SDIO and CAP_VDDSHV_MMC1 should be connected directly to GND if the SDIO_LDO is not used to power VDDSHV5. 

    Regards,
    Paul

  • +1 in reply to peaves
    TI__Guru* 95231 points

    The ROM code will use Legacy compatibility mode at low clock frequency 25MHz, and never attempt to increase frequency, regardless of the SD card capabilities.

    Regards,

    James

  • 0 in reply to JJD
    TI__Genius 16825 points

    Hi James, thanks a lot!