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Altera_Forum
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16 years ago

Constraining PLL in TimeQuest

Hello, I was waondering how to use derive_pll_clocks comand in TimeQuset. TimeQuest can't reflect new frequency. I did... 1.I grenarated SDC File from QSF File. 2.I changed input...
Altera_Forum's avatar
Altera_Forum
Icon for Honored Contributor rankHonored Contributor
16 years ago

Hi wat_arg,

You can try the -create_base_clocks option of derive_pll_clocks. With the option, derive_pll_clocks creates the PLL input clock ('clk' in your case) if the clock is not defined. Of course you need to comment out the input clock definition.

Here are the updated SDC constraints:

derive_pll_clock -create_base_clocks

# create_clock -period "6.666 ns" -name {clk} {clk} ;# commented out