( ESNUG 495 Item 3 ) -------------------------------------------- [11/11/11]
Subject: Yes, Real Intent's Ascent XV does do X's after initialization
> They showed me Ascent XV X verification part which I am interested. It's
> a useful tool, covers static X verification and dynamic X verification.
>
> I think that the drawback is that the main X source is DFF without reset,
> but the Real Intent tool does not cover how to verify whether a DFF is X
> after initialization.
>
> - from http://www.deepchip.com/items/dac11-02.html
From: Lisa Piper <lisa=user domain=realintent not mom>
Hi, John,
This commenter is correct that one X-source reported by Ascent XV (AXV) is
a DFF without a reset. However it's wrong to say that *any* DFF which does
not have a reset will be considered as an X-source by AXV. AXV looks at
reset sequences that can properly initialize a non-resettable DFF to a
known value.
This lets you ID the DFFs that need resets, and those DFFs that don't;
which simplifies routing.
Verification engineers can use our X-accurate models and monitors in RTL
simulation to detect whether they have functional bugs which are hidden by
X-optimism. Ascent XV identifies exactly when and where the X-optimism
occurs, not simply where a control expression has an X value.
Our monitors also let a verification engineer find potential X-sources that
are not taking on an X-value in simulation.
In gate-level verification, Ascent XV helps correct unnecessary X's caused
by X-pessimism; correctly revealing the results of initialization sequences.
- Lisa Piper
Real Intent, Inc. Allentown, PA
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