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AM3352 Boot mode with MMC0 & MMC1

Suresha N S
Expert 1070 points

Other Parts Discussed in Thread: AM3352

Hi all, 

We are designing a system with AM3352 processor. We need to have both SD Card & eMMC as boot options with SD Card being the higher priority.

Since boot mode "11100b" is the only mode containing both MMC1 & MMC0 as boot sources, we have to use this to accommodate both SD Card & eMMC. Since we want to have higher priority for SD Card,  we have to connect SD Card on MMC1 & eMMC (Size- 2GB) on MMC0. 

But the TRM section 26.1.7.5.2 suggests "MMC1 supports booting from eMMC/eSD/managed NAND memory device with 4GB capacity or greater.If you have the need to boot from two different card cages, many MMC/SD cards will boot from MMC1, but for maximum compatibility only MMC0 should be used to boot from the card cage."

What is the meaning of compatibility here ? Can we  connect the SD Card & eMMC as mentioned above ?   If not, is there any alternate methods which we can use to satisfy our boot mode requirement ?

Below discussion suggests that size of the eMMC flash is not a concern in our case.  http://e2e.ti.com/support/arm/sitara_arm/f/791/t/288592.aspx

Looking forward to response.

Thanks & Regards,                                                                                                                           Suresha N S

  • 0
    TI__Guru**** 393215 points
    Hi Suresha,
     
    You can use two different boot modes, for example:
     
    11100b MMC1 MMC0 UART0 USB0
    11000b SPI0 MMC0 USB0 UART0
     
    You can have SYSBOOT2 tied low with a pulldown resistor permamently and also tied high through a button and pullup resistor. You will the boot from SD card on MMC0 by default. When you want to reboot from eMMC on MMC1 you press the button and turn on power and that's it. 
  • 0 in reply to Biser Gatchev-XID
    Prodigy 60 points

    Does MMC1 support booting from a FAT partition on an SD card or not?

    Or said another way, exactly what conditions must be satisfied to successfully load an MLO and uboot.img file from a FAT partition on an SD card in a cage wired to MMC1 on the AM3352?

    Mike

  • 0 in reply to Michael Schaffner
    TI__Guru**** 393215 points

    The recommendation is to use MMC0 for booting from MMC/SD card cage. The AM335X TRM Rev. K, section 26.1.7.5.2 says:

    "If you have the need to boot from two different card cages, many MMC/SD cards will boot from MMC1, but for maximum compatibility only MMC0 should be used to boot from the card cage."