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AM335x 300MHz : PLL configuration in ROM boot loader

Takahiro Ogo
Genius 5940 points

Hi

I know the MPU is provided 500MHz for the A8 after the ROM Boot code configures the PLLs. (from AM335x TRM)

 

So, I have a simply question.

If I use the AM335xxZCE30 (up to 300MHz), Is MPU provided 300MHz, or 500MHz?

 

I think ROM code is same as 500MHz device . So the frequency will be 500MHz.

I feel strange. Because AM335xxZCE30 is not supported  for MPU 500MHz.

 

Best Regards.

 -Takao

  • 0
    TI__Guru* 87000 points

    Takao-san,

    the ROM is the same across all devices.  For the 300MHz devices, your initial bootloader must drop the frequency down to 300MHz to meet the reliability specs of that device.  Continuing to run over 300MHz may cause unpredictable behavior.

    Regards,

    James

  • 0 in reply to JJD
    Genius 5940 points

    Hi, James-san

    Thank you for your reply.

    I can't understand it well yet. Could I ask you a few more questions?

    It is the 300MHz devices and then Why can the bootloader operate wih MPU 500MHz

    Or, Does the 300MHz device assure of MPU 500MHz operation by user's initalization of 300MHz?

    -Takao

     

     

  • 0 in reply to JJD
    Guru 20205 points

    Hi James-san,

    I have the same question.

    The ROM bootloader configures the MPU clock to 500MHz for all devices so that the section 26.1.4.3 in TRM describes it.

    Is it allowed to operate the 300MHz devices with 500MHz until drop it down to 300MHz by user's initialization?

    Best regards,

    Daisuke

     

  • 0 in reply to JJD
    Guru 20205 points

    Hi,

    Please give me an answer as soon as possible.
    Your prompt reply would be appreciated.

    Best regards,

    Daisuke