RE: [sv-ac] Re: Clock flow

I agree with you on both ended and matched.
ed
 

> -----Original Message-----
> From: owner-sv-ac@eda.org [mailto:owner-sv-ac@eda.org] On 
> Behalf Of John Havlicek
> Sent: Wednesday, August 31, 2005 7:27 PM
> To: Manisha_Kulshrestha@mentor.com
> Cc: john.havlicek@freescale.com; sv-ac@eda.org
> Subject: [sv-ac] Re: Clock flow
> 
> Hi Manisha:
> 
> > Is there any specific reason that the instance of a sequence with
> > methods ended/matched are getting excluded in the above case ?=20
> 
> First, I believe that these restrictions can be relaxed without 
> introducing backward compatibility problems.  This is because saying 
> that the clock does not flow through ended/matched means the 
> sequences 
> instances to which these methods are applied must already 
> have initial 
> clocking events defined.  Thus, if the contextual clock flows in, it
> will immediately be overridden by the internal clocks of the 
> sequences.
> 
> As I recall, the intuition for these restrictions was basically that 
> a clock flowing into a sequence instance starts affecting the 
> beginning of that sequence, while ended/matched are references
> to the endpoints of sequences.  Thus, there is something 
> counterintuitive about have the clock flow "backwards" to get to the 
> start of the sequence instance to which ended/matched is applied.
> 
> Also, "matched" involves synchronization between clocks, so I 
> think the
> committee preferred to avoid the clock flow in this case.
> 
> On the other hand, especially with "ended", I think the case can be
> made that it is a nuisance to forbid the clock to flow in.  
> 
> For example, if I want to code my sequences as unclocked and only 
> attach my clock at the top level of a property, then I want 
> that clock 
> to be able to flow to all parts of the property.  If I need 
> to use "ended",
> then I am stuck--I have to declare an explicit clock for each sequence
> to which I want to apply ended, and I have to make sure it 
> matches the clock 
> in the context where ended appears.  This makes those sequences less
> re-usable, or it forces me to a different coding style in which the 
> clock gets passed in as an argument.
> 
> My current opinion is that it would be a good thing to relax this
> restriction for "ended", at least if "ended" is applied to an 
> instance of
> an unclocked sequence.
> 
> In the case of matched, it is less clear to me that it is a good idea
> to relax the restriction.
> 
> I am curious to hear other opinions on this topic.
> 
> Best regards,
> 
> John H.
> 
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> > From: "Kulshrestha, Manisha" <Manisha_Kulshrestha@mentor.com>
> > Cc: <sv-ac@eda.org>
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> > Hi John/All,
> > 
> > In section 17.12.3 (Clock Flow), P1800 draft, it says that:
> > 
> > The scope of a clocking event flows into an instance of a named
> > property. The scope of a clocking event flows into an instance of a
> > named sequence provided neither method ended nor method matched is
> > applied to the instance of the sequence.
> > 
> > Is there any specific reason that the instance of a sequence with
> > methods ended/matched are getting excluded in the above case ?=20
> > 
> > Thanks.
> > Manisha
> > 
>