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AM625: Fallback to USB backup boot takes 10s

Isee
Expert 6550 points
Part Number: AM625

Our boot strappings are configured to boot from eMMC as the primary boot. The backup boot source is set to USB. We noticed that it takes 10 seconds until the USB interface gets enumerated if there is no valid image on the eMMC (empty eMMC device).

Is this 10-second delay for the fallback boot normal? We could not find this number anywhere in the reference manual. I guess there is no option to shorten this delay.

Thank you

Andreas

  • 0
    TI__Guru* 85960 points

    This does seem excessive long.  A couple of questions:

    -are you attempting to perform a DFU or host boot in backup boot mode?

    -Are you operating with VDD_CORE= 0.85V or 0.75V?

    -is VDDA_CORE_USB and VDD_CORE being supplied by the same source at the board level?

    Regards,

    James

  • 0
    TI__Expert 6550 points

    DFU. AM62 being a USB device 

    CTRL_RECOVERY_MICO# is an external signal that we have to force USB DFU mode even when the eMMC is programmed. This is tested working.

    Primary boot mode is also working as expected

    I cannot attach the schematic - will send it privately

  • 0 in reply to Isee
    TI__Guru* 85960 points

    Isee, your response doesn't answer the other two questions:

    -Are you operating with VDD_CORE= 0.85V or 0.75V?

    -is VDDA_CORE_USB and VDD_CORE being supplied by the same source at the board level?

    Regards,

    James

  • 0 in reply to JJD
    TI__Expert 6550 points

    Sorry.

    To your second question, same source.

    first question I will get back to you shortly.

  • 0 in reply to Isee
    TI__Expert 6550 points

    Update - another developer did re-test and was not able to reproduce the issue initially described.

    Maybe this is related to the VDD_CORE= 0.85V vs 0.75V ? In my test I have 0.85V. Could that be the reason? They are re-checking.

  • 0 in reply to Isee
    TI__Guru* 85960 points

    I don't think that could be a cause, but just wanted to check.  Realize that the USB backup boot will only work at VDD_CORE = 0.85V.  Please check back with the developer.  I'm pretty sure the USB DFU will do a series of retries, so may their setup is different enough to establish a quicker enumeration.

    Regards,

    James

  • 0 in reply to JJD
    TI__Expert 6550 points

    Now we understand what is triggering the different behavior.

     If the eMMC is configured the way we need it (send acknowledge, booting from boot area partition 1, 8-bit, reset bus width, SDR high-speed timings) the fallback to recovery (USB DFU) is immediate, if the eMMC is factory configured (so no SDR, no 8-bit, no nothing) the recovery takes up to 10 seconds.

     If this is the expected behavior we will handle it (this is affecting the initial factory programming), I would appreciate a confirmation on that regard.

  • 0 in reply to Isee
    TI__Guru* 85960 points

    Isee, this is good feedback.  I would expect it to be slower, but not by that much. I will have to consult with the ROM team.

    Regards,

    James

  • 0 in reply to JJD
    TI__Guru* 85960 points

    Isee, what are your BOOTMODE pin settings?  

    Regards,

    James

  • 0 in reply to JJD
    TI__Expert 6550 points

    Signal

    Default State (Via Pull Resistor)

    Override

    BOOTMODE_00

    HIGH

    -

    BOOTMODE_01

    HIGH

    -

    BOOTMODE_02

    LOW

    -

    BOOTMODE_03

    HIGH

    Can be pulled low (via recovery mode control signal that pulls BOOTMODE_04 high at the same time - when active)

    BOOTMODE_04

    LOW

    Can be pulled high (via inverted recovery mode control signal that pulls BOOTMODE_03 low at the same time - when active)

    BOOTMODE_05

    LOW

    -

    BOOTMODE_06

    HIGH

    -

    BOOTMODE_07

    LOW

    -

    BOOTMODE_08

    LOW

    -

    BOOTMODE_09

    LOW

    -

    BOOTMODE_10

    HIGH

    -

    BOOTMODE_11

    LOW

    -

    BOOTMODE_12

    LOW

    -

    BOOTMODE_13

    LOW

    -

    BOOTMODE_14

    LOW

    -

    BOOTMODE_15

    LOW

    -
  • 0 in reply to Isee
    TI__Guru* 85960 points

    Hi Isee, apologize for the delay here.  We have confirmed this issue and it  has been reproduced on our EVMs.  It appears that there is a 10sec timeout for eMMC boot mode B6:B3= 1001b as well as MMCSD boot B6:B3 =1000b in filesystem mode (ie, B7=0).  This timeout for MMCSD boot in raw mode (B7=1) is 5 seconds.  

    Unfortunately there is no workaround for this delay.

    Regards,

    James