• State
  • Locked Locked
  • Replies 2 replies
  • Subscribers 98 subscribers
  • Views 177 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

slow (/2) MMC/SD clocking

Armin Inauen
Intellectual 450 points

I have a question about the MMC/SD clock. My board has the following clock settings:

ARM9_0: GEL Output: ---------------------------------------------
ARM9_0: GEL Output: | PLL0 Information |
ARM9_0: GEL Output: ---------------------------------------------
ARM9_0: GEL Output:
ARM9_0: GEL Output: PLL0_SYSCLK1 = 312 MHz
ARM9_0: GEL Output: PLL0_SYSCLK2 = 156 MHz
ARM9_0: GEL Output: PLL0_SYSCLK3 = 26 MHz
ARM9_0: GEL Output: PLL0_SYSCLK4 = 78 MHz
ARM9_0: GEL Output: PLL0_SYSCLK5 = 104 MHz
ARM9_0: GEL Output: PLL0_SYSCLK6 = 312 MHz
ARM9_0: GEL Output: PLL0_SYSCLK7 = 52 MHz

Now I set the MMCCLK register to 0x0101. This should result in an 37.5MHz clock on the SD card.

If I measure the clock (MMCSD0_CLK) with the oscilloscope I only get 19MHz. Also if I set the MMCCLK register to another value, the measured clock is half of the required one.

Measuring SYSCLK2 on the DDR ram shows 150MHz, so the PLL settings seems to be right.

Thanks for any suggestions. 

regards

Armin

  • 0
    TI__Expert 4760 points

    Hi Armin,

    In your case if  DIV4=1  MMC clock = 19.5 MHz .But your register setting shows MMCCLK= 0x0101 in that case DIV4= 0 then you shouls get 39 MHz across MMCSD0_CLK pin.

    Can you please check the CCS register view option to see the actual MMCCLK value hope it should be 0x1101

    Example of DIV4 settings

    DIV4 = 0

    MMC clock = 156 MHz / 2× (1 + 1) = 39 MHz

    DIV4 = 1

    MMC clock = 156 MHz / 4× (1 + 1) = 19.5 MHz

    • --------------------------------------------------------------------------------------------------------
      Please click the Verify Answer button on this post if it answers your question.
      --------------------------------------------------------------------------------------------------------

     

    Regards

    Antony   

  • 0 in reply to Antony Samsunil
    TI__Expert 4760 points

    Hi Armin,

    Can you please close this post if you don't have any further clarification

    Thanks

    Regards

    Antony 

    • --------------------------------------------------------------------------------------------------------
      Please click the Verify Answer button on this post if it answers your question.
      --------------------------------------------------------------------------------------------------------