Subject: Re: [sv-ac] Assume proposals.
From: Adam Krolnik (krolnik@lsil.com)
Date: Wed Sep 17 2003 - 07:33:05 PDT
Hi Joseph;
Proposal #1 is for an assume statement for environmental constraints and for
constrained stimulus generation.
Proposal #2 is for an immediate (boolean) assume statement, for use in design code.
PSL has 4 verification directives for functionality such as this:
assume, assume_guarantee, restrict, restrict_guarantee (these last two, only
for sequences, not properties.)
I can understand a need for part of proposal #1 - constraining a stimulus generator.
But it would seem that if one wants assumptions, they would want both assume and
assume_guarantee types.
The assume statement would be used outside of the design code being verified to
restrict the stimulus/search space to a subset of the legal space.
The assume_guarantee statement would be used inside the design code to define
how the block is intended to be used.
I don't quite see how an immediate assume fits in. I understand how immediate assertion
statements can be used - something instead of "if (!expr) $error()". Joseph, maybe
an example or two to show how you see the immediate assumption being used.
I would like to see assume and assume_guarantee functionality through a combination of
these proposals. This would provide the ability to specify intent of properties
in design code as well as constrain stimulus generation specifically.
Surrendra -
BTW, it seems that the biasing and extra constructs for stimulus generation do not
address temporal constraints. A very simple example is constraining an interface
to 3 transactions in N clocks, or not starting another stimulus source until a
previous one completes.
Thanks for the proposals guys.
Adam Krolnik
Verification Mgr.
LSI Logic Corp.
Plano TX. 75074
Co-author "Assertion Based Design"
This archive was generated by hypermail 2b28 : Wed Sep 17 2003 - 07:34:28 PDT