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Altera_Forum's avatar
Altera_Forum
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16 years ago

Problem in generating clock from constrained PLL clock

Hi all,

I am using Time quest for constraining clocks. I was able to constrain PLL clock from "derive_pll_clocks". In my case i have to generate other clocks from this PLL clock, i am trying to constrain those clocks by generating in time quest. But i am not able to do so, please guide me.

FYI:This is the command for generating clock,

# create_generated_clock -name {serialCommRxSynchronizeSignal} -source [get_ports {SYSTEM_CLOCK_MAIN_1}] -divide_by 2 [get_nets {PLL_12|altpll_component|_clk0}]

serialCommRxSynchronizeSignal - Clock to be generated

SYSTEM_CLOCK_MAIN_1 - System Clock

clk0 - PLL output

Thank you.

1 Reply

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

    Your command makes no sense: you have three clocks there.

    By "PLL clock", I assume you mean a PLL output clock.

    The syntax for create_generated_clock is

    create_generated_clock -name <name> -source <sourceClock> -divide_by 2 <targets>

    <name> is just that, a pretty name to give to it.

    <sourceClock> is the source clock object.. If your clock is being generated from a PLL output clock, then it will be something like

    [ get_pins -hierarchical {PLL12|altpll_component|auto_generated|pll1|clk[0]} ]

    <target> will be the objects where your generated clock comes from. Typically, it will be a register or so.