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  1. #1
    Newbie level 3
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    when neg. edge flop followed by pose. edge flop both have different clock then locku

    use of lockup latch is for resolve hold violation but doubt is that the when neg. edge flop followed by pose. edge flop both have different clock then lockup-latch is required or not ???

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  2. #2
    Advanced Member level 5
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    Re: when neg. edge flop followed by pose. edge flop both have different clock then lo

    Positive, negative edge have nothing to do with it.
    The problem is non-determinstic, non-stable phase
    relation between clocks.

    A negative edge FF followed by a positive edge FF
    will do the metastability-scrubbing job if the two
    "different" clocks are same frequency and have a
    fixed phase relation (as would, say, two branches
    of the same master clock source / clock product).
    Provided that regular old timing margin is met,
    Clkb-Q1-Clk-Q2.



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