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BQ34Z100EVM: Cannot seal - stuck in unsealed state

Julian Eyre
Prodigy 240 points
Part Number: BQ34Z100EVM
Other Parts Discussed in Thread: BQSTUDIO, BQ34Z100

I have been successfully using the BQ34Z100EVM for several weeks now, and was able to transfer between sealed, unsealed and full access modes.  However, recently I have found that the device refuses to transition away from an unsealed state.  Strangely, after a power cycle or reset the chip defaults to a sealed state, as expected, and I am able to transition to an unsealed state with no problem, indicating that the access keys for this are correct.  However, when I try to return to a sealed state using the control sub-command 0020h, it refuses to do so.

I am also unable to transition to full access mode, although I am sure that the default key (FFFFFFFFh) has not been changed.  I have tested this with both my own microcontroller code and with the Battery Management Studio with the same results.  All other device functions are functional, such as reading/writing flash locations.

Does anyone have any idea why this is happening?

  • 0
    TI__Mastermind 42535 points

    Hi Julian,

    The sealed command should work. If it doesn't you can POR the device in which case it will come up again as sealed, or flash the fw again. The sealed mode only forces the fw to set a bit that prevents outside access to df. So, once the device gets the command, it will set the appropriate bits and to into the state.

  • 0 in reply to Batt
    Prodigy 240 points

    Hi Batt,

    Thanks for the reply.

    A POR does indeed set the seal bit as expected.  However, as soon as I unseal the device (for access to data flash) I cannot reseal it using the seal command for some reason.  Furthermore, the device refuses to enter Full Access mode which means that the FW cannot be flashed as it cannot go into ROM mode.  Basically, the FAS and SS bits cannot be changed once the device is in an unsealed state (other than using a POR).

    Julian

  • 0 in reply to Julian Eyre
    TI__Mastermind 42535 points

    Please redownload the bqstudio. At the moment it looks like it's a bqz corruption issue for you.

  • 0 in reply to Batt
    Prodigy 240 points

    Hi Batt,

    I have uninstalled, re-downloaded and reinstalled BQStudio several times to no effect.

    I cannot re-flash the device in any event as it will not switch to Full Access mode.

    And it is not a BQStudio problem as my own host processor code cannot switch the device to either sealed or Full Access mode once in an unsealed state.  Even a reset command does not reliably switch it to a sealed state.  Only a power cycle will do that.

    Julian

  • 0 in reply to Julian Eyre
    TI__Mastermind 42535 points

    Julian,

    We have not seen these issues with sealing and unsealing. If you have the same key for unseal and full access your device will be stuck. Other than that, the device should respond to back to back commands for unseal and full access. Try to send the commands within a 2s interval.

  • 0 in reply to Batt
    Prodigy 240 points

    I have never changed the key for Full Access (it should still be 0xFFFFFFFF).  The key for unseal is definitely the default value as I am able to unseal the device if it is in a sealed state after a power cycle using the default key.

    When you say stuck, are you saying that the device would be unusable and need replacing?

    I do not recall seeing any warning in the documentation regarding the danger of setting the two keys to be the same value.  Given that it would produce such a bad result, I think such a warning would be needed. Either that, or the BQ34Z100 firmware should disallow the setting of the two keys to be the same.

    I have tried sending the two commands back to back with a delay between.  I did this using both the BQStudio and my own code.  There is no effect.  Once unsealed, it will not seal nor go to Full Access.

    All other functions are completely functional, including access to flash.

    Regards,

    Julian

  • 0 in reply to Julian Eyre
    TI__Mastermind 42535 points

    Yes, if the default unseal and full access keys are the same you will need to replace the device if it has been sealed. This is because you won't be able to unseal it and reflash fw.

    You are right, there are no warnings. It would be useful to include a line in the TRM about the same.

    Unfortunately, I'm not able to verify out your results here. When flashed with v0.16, the device unseals and goes into full access from sealed state on our device.