RE: [sv-ec] final block scheduling

I think the statement in the LRM "Unlike an initial block, the final
block does not execute as a separate process; instead, it executes in
zero time, the same as a function call" is misleading; especially the
part the separate process. I think the intent was to say that all the
final blocks execute as a single process that begins after $finish
removes all the other active or inactive events. That essentially means
there is an implicit function call the calls all of the final blocks as
if they were functions. We should probably state that simulation is over
once that implicit function call returns, even if are additional active
events.


Dave


> -----Original Message-----
> From: owner-sv-ec@eda.org [mailto:owner-sv-ec@eda.org] On Behalf Of
Gordon
> Vreugdenhil
> Sent: Friday, August 26, 2005 8:40 PM
> To: Arturo.Salz@synopsys.com
> Cc: 'Clifford E. Cummings'; sv-ec@eda.org
> Subject: Re: [sv-ec] final block scheduling
> 
> 
> Just to clarify here -- I don't think that I claimed to Cliff
> that final blocks are reactive (I certainly couldn't find such
> a claim in the email history).  This is a good thing because
> they don't execute in the reactive region or really in any
> region.  In Cliff's specific example, the process containing
> the $finish is reactive so the NBA in the module is guaranteed
> to mature prior to the $finish being encountered in the
> reactive process.
> 
> Certainly once a $finish is encountered no further activity
> occurs in the sequential block nor can any activities be
> scheduled.  It could be open for discussion whether pending
> scheduled activities should be permitted to mature, historically
> that hasn't been permitted and I suspect that this would be
> more confusing than helpful in general.
> 
> I believe that Arturo's opinion is in line with mine -- once
> $finish occurs, the current thread terminates immediately, no
> futher actions are scheduled or permitted to mature, and the final
> blocks are run.  Clearly there is enough room in the interpretation
> of the spec that activities such as continuous assign updates
> that would be activated from the sequential block prior to the
> $finish may or may not mature.  In fact, any pending same-region
> activity may or may not mature since that is up to the simulator's
> decisions about thread interleaving.  However, what I think is
> pretty definite is that once a $finish is evaluated, no futher
> action in that thread is permitted and no further region changes
> occur.  The only possible activity would be activity that the
> simulator *could have* scheduled prior to the $finish being
> executed.
> 
> Gord.
> 
> 
> 
> Arturo Salz wrote:
> > Cliff,
> >
> > I'm not sure whether a final block should execute in the Reactive
> region, or
> > execute as a function that is called from within $finish. However, I
do
> > believe that if the final block creates additional events then those
> events
> > should not be allowed to mature (i.e. execute). I suspect this what
you
> are
> > observing when you execute your example: the $strobe calls are
> essentially
> > posting events into the Postponed region, which are never executed.
> >
> > 	Arturo
> >
> > -----Original Message-----
> > From: owner-sv-ec@eda.org [mailto:owner-sv-ec@eda.org] On Behalf Of
> Clifford
> > E. Cummings
> > Sent: Friday, August 26, 2005 5:08 PM
> > To: sv-ec@eda.org
> > Subject: [sv-ec] final block scheduling
> >
> > Hi, All -
> >
> > I have attached a final block example that I have run on ModelSim. I
> don't
> > think it is working yet on VCS (forgive me if this is a mis-
> representation).
> >
> > The example did not work as I expected.
> >
> > 10.7 Final blocks
> > The final block is like an initial block, defining a procedural
block of
> > statements, except that it occurs at the
> > end of simulation time and executes without delays. A final block is
> > typically used to display statistical information
> > about the simulation.
> >
> >
> > Based on this definition, I thought I could put $strobe commands
into a
> > final block and have the strobes execute before simulation finished.
> >
> > Gord and I have exchanged email messages on this and he believes the
> final
> > block should execute in the Reactive region(s), and complete the
$finish
> > before the $strobes can execute in the postponed region. I wanted to
see
> > the $strobed results too since I frequently $strobe final simulation
> > results (then do a #1 $finish; - I have always hated the #1 in front
of
> the
> > $finish and I thought the final block could get me away from this
ugly
> > extra delay).
> >
> > Opinions? The final block can have any command currently legal in a
> > function, but if $strobe is never executed in a final block, then it
> should
> > be an error to avoid final-block-usage confusion.
> >
> > Regards - Cliff
> >
> > ----------------------------------------------------
> > Cliff Cummings - Sunburst Design, Inc.
> > 14314 SW Allen Blvd., PMB 501, Beaverton, OR 97005
> > Phone: 503-641-8446 / FAX: 503-641-8486
> > cliffc@sunburst-design.com / www.sunburst-design.com
> > Expert Verilog, SystemVerilog, Synthesis and Verification Training
> >
> >
> 
> --
> --------------------------------------------------------------------
> Gordon Vreugdenhil                                503-685-0808
> Model Technology (Mentor Graphics)                gordonv@model.com