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CC3220MODA: memory clear during hibernation

YunJung Kim
Intellectual 295 points
Part Number: CC3220MODA

Hi, 

I'd like to know what will happen to RAM during hibernation. 

Especially memory fragmentation, is there any possibility that fragmented memory remains after hibernation(RTC wake-up).

Would it be okay to regard both cold-boot/POR and wake-up-from-hibernation is same in RAM standpoint?

Thanks,

Yun

  • 0
    Guru 73215 points

    Hi Yun,

    There is no RAM memory retention at hibernation mode (if we not count few bytes of RTC and retention registers). If you need RAM retention you need to use LPDS (low power deep sleep. Power management of CC3220 device is described at this video.

    Jan

  • 0 in reply to Jan D
    Intellectual 295 points

    Hi Jan,

    I understand there is no retention at HIB mode and I'm using retention registers for this purpose.

    What I'm asking is if it is 100% sure that RAM fragmentation will be cleared after hibernation.

    Thanks,

    Yun

  • 0 in reply to YunJung Kim
    Guru 73215 points

    Hi Yun,

    Sorry, I don't understand your question, because it really not make sense. How do you expect that content of RAM can retain if RAM is not powered at HIB?

    btw ... content of RAM si cleared by ROM bootloader after POR or exit HIB from security reasons.

    Jan

  • 0 in reply to Jan D
    Intellectual 295 points

    Hi Jan,

    A weird bug that makes a bad_alloc exception which is recovered itself accidentally led to this weird question.

    (This application runs seconds and enters HIB hours repeatedly)

    And I wasn't able to find a description of RAM behavior during hibernation so I guessed if the RAM power is not intentionally off, this could happen.

    If you have, could you share a link or document number I can read about the details?

    Thanks!

    Yun

  • 0 in reply to YunJung Kim
    Guru 73215 points

    Hi Yun,

    I am not aware about any official documentation. This topic was discussed few times at e2e forum. You can try to search for this older threads.

    Your application should be designed according this two facts:

    • there is no RAM retention at HIB
    • RAM state after startup is not determined (that means behaviour same as almost any MCU at market)

    If you think that your application code can be affected by undetermined/previous state of RAM, you should change this. Because this is definitely not correct.

    But if I should guess, I think that reason of you issues lies somewhere else then not determined state of RAM after startup.

    Jan

  • 0 in reply to Jan D
    Intellectual 295 points

    Hi Jan,

    Thanks for your advice!

    Yun