• State Resolved
  • Locked Locked
  • Replies 3 replies
  • Answers 1 answer
  • Subscribers 99 subscribers
  • Views 454 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.

MMCSD/SPI clocking signals on J15 expansion connector

Petr Duga
Intellectual 495 points
Other Parts Discussed in Thread: TMS320C6748

Hi, I want to make a medium wave AM radio receiver. For AM demodulation I will use a waveform generator AD5932, that I want to programm with my C6748 LCDK (456MHz). I will connect it via expension connector J15. I need two clocking signals for SPI (up to 40 MHz) and for clocking of AD5932 (50 MHz ideally). I have two questions:

1) What is the value of  function clock frequency from equation: (spruh79a,page 1197)

memory clock frequency = function clock frequency/(2 × (CLKRT + 1))

2) May I use MMCSD_CLK for SPI "clocking" instead of SPI0_CLK?

Thanks for your answers.

Petr Duga

  • 0
    TI__Mastermind 20790 points

    Petr Duga,
    Welcome to E2E forum. I can suggest some comments,
    1. You will get some more details about function clock frequency from someone better able to help.
    2. I think so, MMCSD_CLK is up to 400KHz. However you needed up to 40MHz for SPI.

    See the note in section "MMC/SD Controller Initialization"
    The MMC/SD cards require a clock frequency of 400 kHz or less for the card initialization
    procedure.

    And also refer section "Card Identification Operation" in TMS320C6748 TRM.
    NOTE: The following steps assume that the MMC/SD controller is configured to operate in MMC or
    SD mode, and the memory clock frequency on the MMCSD_CLK pin is set for 400 kHz or
    less.

  • 0 in reply to Pubesh
    TI__Expert 4760 points

    Hi Pert Duga,

    From your post I understand you need two clock source one is for SPI 40 MHz and other one is for AD5932 50 MHz

    Answers to you questions

    1. The Value of the function clock frequency = PLL0_SYSCLK2 (in your case it is 228 MHz)

    2. You can’t use MMCSD_CLK for SPI clocking SPI data is latched based on the SPIx_CLK rising or falling edge that is not in phase with MMCSD_CLK.

    My suggestion is to use the separate clock oscillator for AD5932 without disturbing other clock source

    Regards

    Antony

    • --------------------------------------------------------------------------------------------------------
      Please click the Verify Answer button on this post if it answers your question.
      --------------------------------------------------------------------------------------------------------
  • 0 in reply to Antony Samsunil
    Intellectual 495 points

    Pubesh, Antony, thank you for your answers!

    It seems not to be a good idea to use MMC/SD. I will use just SPI clock or an other clock source, how said Antony.

    Have a nice day.

    Petr Duga