RE: [sv-bc] Re: Fwd: Re: Priority / Unique Errors

> -----Original Message-----
> From: Steven Sharp [mailto:sharp@cadence.com]
> Sent: Friday, April 08, 2005 11:53 AM
> To: Arturo.Salz@synopsys.com; sharp@cadence.com; sv-bc@eda.org;
> cliffc@sunburst-design.com; Rich, Dave
> Subject: RE: [sv-bc] Re: Fwd: Re: Priority / Unique Errors
> 
> 
> >From: "Rich, Dave" <Dave_Rich@mentorg.com>
> >
> >[DR>] That is why I tried to propose that the default branch of a
> >priority/unique case statement not be part of the check, and only get
> >executed if there is a violation. Having a default branch in a p/u
case
> >statement is currently useless.
> 
> It is useless in a priority case, since the check will never fail when
> there is a default.  Conversely, if the action on a failure in a
priority
> case is to execute the default, as you propose, it is pretty pointless
to
> declare it as` a priority case.  An ordinary case already executes the
> default when no other case item matches, so declaring it priority
wouldn't
> change anything.
[DR>] I said the default branch would not be a part of the priority
check. That means the check will *only* fail if it executes the default.
> 
> I am not convinced that a default is useless in a unique case.  You
might
> have a default to handle a set of values that are too complex to
specify
> explicitly, but still want a failure if multiple explicit case items
> matched.
[DR>] 
True, but I don't think a hardware designer thinks of having parallel
encoded logic as having a branch that's complex to explicitly specify.
> 
> Perhaps you are assuming that a default is treated as an "always
match",
> which would automatically result in a failure if an explicit case item
> matched also.  That is not how I interpret it.  I already assume that
the
> default is not part of the multiple match portion of the unique check.
> The default is only considered if none of the other items match, so it
> can never match at the same time as another item.
> 
> 
> >I would rather we take some functionality out than let poorly
understood
> >functionality go in. Spend the proper amount of time to get it right.
> 
> Are you suggesting that priority and unique be removed from the P1800
LRM?
> 
> Steven Sharp
> sharp@cadence.com