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MMC1 boot mode, 1-Bit MMC or 4-Bit SD?

Jun Ma81458
Prodigy 80 points

Other Parts Discussed in Thread: AM3715

Hello,

I built my own prototype with AM3715 CUS chips. A SD card holder is connected to MMC1, and the power supply for MMC1 is 3.0V. I set the SYS_BOOT[5:0] to "010010", that means the processor will use the MMC1 as the 1st boot device. I copied a MLO to my SD card, but the processor doesn't seem to boot from SD card. I measured the signals of SD card holder, I found that the SD_CLK, SD_CMD, and SD_DATA0 have outputs. But SD_DATA[3:1] are kept high.

It looks like the processor working on 1-bit SD I/O mode. I formatted my SD card with FAT32, and only one MLO file is on it.

Can any one give me some hint about how to make the MMC1 works at 4-bit SD mode in booting phase?

Regards,

Jun

  • 0
    Guru 31670 points

    Jun,

    I am not sure about the bootrom code. But in general the sequence is like this. The driver will start with 1-bit mode first and then read the capabilities of the card and check whether it supports 4-bit mode and then issue a switch command and then switches the mode to 4-bit mode. Similarly for high speed etc. 

  • 0 in reply to Renjith Thomas
    Guru 31670 points

    Did you check this table 26-27 in the TRM? 

    Pins Used for MMC1 Boot 
    Signal name Pin  Used in Device
    clk                       gpmc_csn1
    cmd                    gpmc_csn2
    dat0                    gpmc_ad0
    dat1                    gpmc_ad1
    dat2                    gpmc_ad2
    dat3                    gpmc_ad3

    Are you using these pins or other the other multiplexed pins for your MMC connector?

  • 0 in reply to Renjith Thomas
    Expert 1130 points

    Hi,

     i think the boot rom supports only 1 bit mode

    Regards

    Jethin

  • 0
    Prodigy 20 points

    Hi Jun,

    Have you see below messages output from debug port? If yes, it means MLO load succeed by boot rom, but init MMC1 failed in x-loader. To fix this, you have to modify x-loader and u-boot source codes to add MMC1 boot up support.

    -----------------------------------

    Starting X-loader on MMC

    MMC init failed

    -----------------------------------

    Rick

  • 0 in reply to Jethin Sekhar
    Prodigy 80 points

    Hi Jethin,

    I believe boot rom code support 1-bit mode only. I tried different MMC card, only some 2GB and 4GB micro SD card can be used for booting the board. And full size SD card, all 8GB/16GB micro SD card can NOT boot the board.

    Does anyone experience the same?

    Regards,

    Jun