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Altera_Forum's avatar
Altera_Forum
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10 years ago

DSP Dev Kit PLL Output Pins Question

I have the DSP development kit that has the Cyclone 2. It has SSRAM and some DDR2 memory. I am testing the SSRAM. I have it working at 100 MHz. In the top level code I am using a PLL to generate 3 clocks: 100 MHz, 100 MHz@180 deg, and 200 MHz (for SignalTap). The SSRAM has a clock that is permanently tied to pin R25. My top level code simply takes the PLL output, C1, and assigns it to sram_clk ( c1 => sram_clk). This works but it generates a WARNING telling me to use a dedicated PLL output pin.

How do I connect a dedicated PLL output pin to R25?

How do I find what the PLL output pin(s) are being used?

Thanks,

SwimTeam

2 Replies

  • Altera_Forum's avatar
    Altera_Forum
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    10 years ago

    --- Quote Start ---

    ... it generates a WARNING telling me to use a dedicated PLL output pin.

    --- Quote End ---

    If I recall correctly, the Quartus warning is that using a non-dedicated PLL output may result in more jitter. Your design will likely still work correctly.

    --- Quote Start ---

    How do I connect a dedicated PLL output pin to R25?

    --- Quote End ---

    You can't. The PLL output pins needed to be assigned when the PCB was designed.

    --- Quote Start ---

    How do I find what the PLL output pin(s) are being used?

    --- Quote End ---

    After synthesizing the design, open the pin planner (Assignments->Pin Planner).

    Look for the PLL output pins in that view. You can also download the pinout PDF for the specific Cyclone 2 package you are using, and find the PLL output pins in that PDF, and then look at the Pin Planner view to see where they are located.

    Cheers,

    Dave
  • Altera_Forum's avatar
    Altera_Forum
    Icon for Honored Contributor rankHonored Contributor
    10 years ago

    Thanks.

    It took a day to get it working at 100 MHz. The trick was to get the correct Cypress data sheet and follow the timing diagrams. Using SignalTap my code writes and reads all locations. You are correct because if jitter was a problem it wouldn't work. Won't worry about it

    I'll check Pin Planner.

    Swimteam.