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Altera_Forum's avatar
Altera_Forum
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15 years ago

Error generating ATLPLL for Cyclone III

Hi,

I tried to to generate code for PLL with Megawizard plugin manager. I used multiply factor as 114 and division factor as 7. My input clock frequency is 16 MHz. When I compile the design, I get the following error:

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Error: Can't implement PLL "pll:pll_i|altpll:altpll_component|pll_altpll:auto_generated|pll1" as Cyclone III PLL type

Error: Can't implement clock multiplication and clock division parameter values for PLL "pll:pll_i|altpll:altpll_component|pll_altpll:auto_generated|pll1"

Error: Can't implement PLL because Division and Multiplication cannot be achieved

Critical Warning: Input frequency of PLL "pll:pll_i|altpll:altpll_component|pll_altpll:auto_generated|pll1" must be in the frequency range of 15.0 MHz to 15.99 MHz for locking

Warning: Can't achieve requested value multiplication of 114 for clock output pll:pll_i|altpll:altpll_component|pll_altpll:auto_generated|wire_pll1_clk[0] of parameter multiplication factor -- achieved value of multiplication of 244

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Is there something I am doing wrong? I thought i could generate PLL with any multiplication and division factor as long as it falls between 1 and 512. any help is appreciated.

Thanks,

5 Replies

  • Altera_Forum's avatar
    Altera_Forum
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    The requested VCO frequency is oustside the specified range of 600 to 1300 MHz. As a (somewhat dubious) workaround, you may want to specify an input frequency of 15.95 MHz.

  • Altera_Forum's avatar
    Altera_Forum
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    The PLL must find a least common multiple frequency for the VCO based on the input clock frequency and the mulitply/divide values (for all PLL outputs) that is in the range for the device (600 - 1300 MHz as pointed out by FvM).

  • Altera_Forum's avatar
    Altera_Forum
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    How do we know the VCO frequency? Is there a simple way to know that given my input clock frequency , multiply and divide factors?

    I am only generating one output clock from this PLL.

    Thanks
  • Altera_Forum's avatar
    Altera_Forum
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    --- Quote Start ---

    How do we know the VCO frequency?

    --- Quote End ---

    It's displayed by the MegaWizard.
  • Altera_Forum's avatar
    Altera_Forum
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    Can I calculate by hand given Multiply, divide factors and input clock?