RE: [sv-ac] reminder to vote on mantis 1550

Hi John,

I have been looking at Clause 9 of the LRM and could not find anything
specific with regards to  the value of expressions in the preponed
region at time 0. Perhaps I am looking at the wrong place.

Also, it is not just sampled value at time 0, but also $past (and the
other sampled value functions) that depend on values at clock ticks in
the past (<0). This is why I think that there should be something said
about these values, along the lines I mentioned earlier - the default
and values at declarations are assumed to exist from time -oo. Perhaps
we should add that expressions dependent on these <0 values are also
evaluated to get their values ate time <0.  I agree with your thought
process.

Best regards,
edd

 

> -----Original Message-----
> From: John Havlicek [mailto:john.havlicek@freescale.com] 
> Sent: Thursday, January 25, 2007 8:14 PM
> To: Eduard.Cerny@synopsys.COM
> Cc: john.havlicek@freescale.com; Eduard.Cerny@synopsys.COM; 
> sv-ac@eda-stds.org
> Subject: Re: [sv-ac] reminder to vote on mantis 1550
> 
> Hi Ed:
> 
> I don't think we are complicating anything.
> 
> I think that the preponed value of an expression in the time 0 slot 
> is already defined by the scheduling algorithm.
> 
> So you should be able to delete this text entirely and just say
> that for _every_ time slot, a call to $sampled in that time slot
> returns the preponed value of its argument in that time slot.
> 
> If you say that in the time 0 slot $sampled follows a different rule,
> then that is complicating things.
> 
> Try this thought experiment.  Suppose that there is an expression e 
> that combines some static variables with declaration assignments.  
> Suppose that no assignment in the time 0 slot changes these
> variables.  Should a call to $sampled(e) in the time 0 slot yield
> a different result than a call to $sampled(e) in the time 1 slot?
> 
> My opinion is "no".
> 
> J.H.
> 
> > X-MimeOLE: Produced By Microsoft Exchange V6.5
> > Content-class: urn:content-classes:message
> > Date: Thu, 25 Jan 2007 13:43:00 -0800
> > Thread-Topic: [sv-ac] reminder to vote on mantis 1550
> > Thread-Index: AcdAxdG186prUgy2SBOcNKMORR/kCAAA4F8A
> > From: "Eduard Cerny" <Eduard.Cerny@synopsys.com>
> > Cc: <sv-ac@eda-stds.org>
> > X-OriginalArrivalTime: 25 Jan 2007 21:43:01.0498 (UTC) 
> FILETIME=[C967DDA0:01C740C9]
> > 
> > Hi John,
> > 
> > This is exactly what I wanted to avoid, having to evaluate the
> > expression based on the initial assigned and default 
> values. I.e., in
> > the case of an expression, just use the default value of 
> its type. But
> > if the majority thinks that it is more appropriate to do wht you
> > suggest, fine. But we are here dealing with a corner case, 
> because in
> > most applications, a disable iff  or $assertoff takes care 
> of time 0. Is
> > it worth complicating it?
> > 
> > ed
> > 
> 

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