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Altera_Forum's avatar
Altera_Forum
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14 years ago

UP clock signals with 27MHz input

I'm using the 'clock signals for DE-series board peripherals' core which uses the external 27MHz crystal connected to the clk_in_secondary input to get a 12.288MHz out which i connected to the AUD_XCK.

I cannot get this to work!!! is there anything else that has to be done to use the 27MHz crystal? i basically just connected the CLOCK_27 to the said secondary input in the top level like i would with the 50MHz (i.e CLOCK_50)

I am now using an ALTPLL for 12.5MHz running from 50MHz and it works fine!

5 Replies

  • Altera_Forum's avatar
    Altera_Forum
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    14 years ago

    And for 27MHz ALTPLL doesn't work? Basically, 27MHz clock is commonly used in video applications.

  • Altera_Forum's avatar
    Altera_Forum
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    14 years ago

    No, basically the clock signals core requires a 27MHz signal to generate the audio clock but i cannot get the audio chip to work at all using this clock.

    I can only get the audio codec to work when driven by a ALTPLL core with 50MHz input.

    What i am asking is, do i need to do anything else to use the 27MHz crystal? i'm only thinking this because it looks like the 27MHz crystal is connected to the video chip.

    maybe i should just stick with using ALTPLL, it seems to work fine i guess
  • Altera_Forum's avatar
    Altera_Forum
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    14 years ago

    --- Quote Start ---

    No You don't need 27MHz if it's not needed by the application.

    --- Quote End ---

    Maybe my question wasn't very clear?

    I want to know if the 27MHz crystal on board the DE2 is readily available (as the 50MHz clock is) as an input to various ip core that requires this clock frequency. Because it doesn't appear to be the case

    It looks like the 27MHz crystal is connected to the video chip so i though something might need setting to make it available.