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GreenLantern's avatar
GreenLantern
Icon for New Contributor rankNew Contributor
2 years ago
Solved

PLL constraint issues

Getting this hold timing error. Need help resolving it. PLL cross checking found inconsistent PLL clock settings: Clock: i_DAC_TOP|i_PLL|pll_inst|altera_pll_i|general[0].gpll~FRACTIONAL_PLL|vcoph[...
Timing
  • sstrell's avatar
    sstrell
    2 years ago

    No, you didn't have to break out the PLL output clocks like that. derive_pll_clocks is fine. I was referring to the 3 extra create_clock statements you have (sclk, clk_divider...). Those are coming from internal registers, not an input port of the device, so they should be in your .sdc as create_generated_clock commands, not create_clock.

    As for the failing paths, those look like they are going to Signal Tap, which is debug logic that will be eventually removed. You don't really need to meet timing there.

sstrell's avatar
sstrell
Icon for Super Contributor rankSuper Contributor
2 years ago

No, you didn't have to break out the PLL output clocks like that. derive_pll_clocks is fine. I was referring to the 3 extra create_clock statements you have (sclk, clk_divider...). Those are coming from internal registers, not an input port of the device, so they should be in your .sdc as create_generated_clock commands, not create_clock.

As for the failing paths, those look like they are going to Signal Tap, which is debug logic that will be eventually removed. You don't really need to meet timing there.

  • GreenLantern's avatar
    GreenLantern
    Icon for New Contributor rankNew Contributor
    2 years ago

    Excellent! That is extremely helpful! Thank you!

    As for the create_generated_clock command, could you point out to an article or suggest me how to get the template for them? How do I get their source (sclk,clock_divider2 etc.)?

    Thank you!