when neg. edge flop followed by pose. edge flop both have different clock then locku

alp507 · Dec 30, 2019

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 ???

dick_freebird · Dec 31, 2019

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.

when neg. edge flop followed by pose. edge flop both have different clock then locku

alp507

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dick_freebird

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when neg. edge flop followed by pose. edge flop both have different clock then locku

alp507

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dick_freebird

Advanced Member level 7

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