Subject: RE: Initial Blocks fail with Synopsys Tools
From: Gilbert Nguyen (nguyen@ibiquity.com)
Date: Mon Oct 08 2001 - 10:07:23 PDT
Paul,
Design-Compiler issues warnings for incomplete sensitivity lists also
and it should give warnings about not synthesizing initial blocks.
Furthermore,I believe that initial blocks should be ignored at
synthesis.
Initial blocks allow for conditions that a simulation testbench desires
but may not be real at gate level(gates power up at an unknown state (1
or 0))
& one either have to propagates these unknown 'X' or reset to get to a
known state
so that RTL & gate level simulation matches.
Gilbert
-----Original Message-----
From: Paul Graham [mailto:pgraham@cadence.com]
Sent: Monday, October 08, 2001 11:46 AM
To: cliffc@sunburst-design.com
Cc: vlog-synth@eda.org
Subject: Re: Initial Blocks fail with Synopsys Tools
>
> I was very surprised to learn that Synplicity ignored initial blocks.
I
> consider this to be a serious flaw in the Synplicity tools.
As someone pointed out, Synplicity ignores initial blocks with a
warning.
Ambit also ignore initial blocks with a warning. This could result in
simulation mismatches, but not necessarily. There are other situations
that
could result in simulation mismatches for which Ambit also issues a
warning,
not an error. For instance, an incomplete sensitivity list is flagged
as a
warning. What do other tools do?
Paul
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