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SDRAM with PLL reconfiguration!

thomas yang78259
Intellectual 950 points

hello, everyone.

During the situation when my program CODE had loaded into external SDRAM and the CODE execute from external SDRAM, I need to reconfigure C674x PLL to lower the PLL out from 600M to 400M, can I keep SDRAM context same as before. I know the SDRAM have a refresh time, such as 64ms, During the PLL reconfiguration, the SDRAM refresh can continue?if it can not continue, the SDRAM context will lost no doubt, which worry me very much.  

someone help!

 

  • 0
    TI__Genius 14965 points

    Hi,

    It depends on PLL lock time which can be calculated with following formula:

    PLL Max Lock Time = (2000 x N)/root(m)
    where N = Pre-divider Ratio
          m = PLL Multiplier

    If the lock time is less than 64ms, you should be fine.

    Regards,

    Hyun

  • 0 in reply to Hyun Kim
    Intellectual 950 points

    Hi, hyun.

    I do not think what you said will work well, because I have a try today and I lost my code which locate in SDRAM. and now, I have a idea that I will configure the SDRAM into

    self-refresh mode and then reconfig the PLL, and then make SDRAM out from self-refresh mode into auto-refresh mode.

    I think it will work well, what about you, hyun?

    thank you for your advise.

    thomas