RE: [sv-ac] $past - number_of_ticks proposal

 I think that number_of_ticks should be a (compile time) constant
expression. Is it necessary to introduce another Mantis item for that?

Regards,
ed


> -----Original Message-----
> From: owner-sv-ac@eda.org [mailto:owner-sv-ac@eda.org] On 
> Behalf Of Korchemny, Dmitry
> Sent: Sunday, March 18, 2007 10:50 AM
> To: Bresticker, Shalom; Clifford E. Cummings; sv-ac@eda.org
> Subject: RE: [sv-ac] $past - number_of_ticks proposal
> 
> Hi Shalom,
> 
> The second argument of $past may definitely be a constant expression.
> 
> Dmitry
> 
> -----Original Message-----
> From: owner-sv-ac@server.eda.org 
> [mailto:owner-sv-ac@server.eda.org] On
> Behalf Of Bresticker, Shalom
> Sent: Friday, March 09, 2007 9:42 AM
> To: Clifford E. Cummings; sv-ac@server.eda.org
> Subject: RE: [sv-ac] $past - number_of_ticks proposal
> 
> Why could it not be at least a constant_expression?
> 
> Shalom
> 
> > -----Original Message-----
> > From: owner-sv-ac@server.eda.org [mailto:owner-sv-ac@server.eda.org]
> > On Behalf Of Clifford E. Cummings
> > Sent: Friday, March 09, 2007 9:34 AM
> > To: sv-ac@server.eda.org
> > Subject: [sv-ac] $past - number_of_ticks proposal
> > 
> > Hi, All -
> > 
> > A clarification question came up in one of my SystemVerilog classes
> > regarding the $past number_of_ticks argument. A student questioned
> > whether the argument could be an expression and I believe the answer
> > is no, but LRM does not definitively make a precise 
> definition. There
> > is no BNF to describe the $past arguments.
> > 
> > I did a SVDB search on number_of_ticks and only found Mantis item
> > 1591, which did not cover the topic.
> > 
> > Proposal (if my assumption is correct):
> > 
> > 17.7.3 Sampled value functions
> > Bottom of page 247
> > 
> > WAS:
> > number_of_ticks must be 1 or greater. If number_of_ticks is not
> > specified, then it defaults to 1. $past returns the sampled value of
> > the expression that was present number_of_ticks prior to the time of
> > evaluation of $past. A clock tick is based on clocking_event. If the
> > specified clock tick in the past is before the start of simulation,
> > the returned value from the $past function is a value of X.
> > 
> > PROPOSED:
> > number_of_ticks must be an integer constant of 1 or greater. If
> > number_of_ticks is not specified, then it defaults to 1. $past
> > returns the sampled value of the expression that was present
> > number_of_ticks prior to the time of evaluation of $past. A clock
> > tick is based on clocking_event. If the specified clock tick in the
> > past is before the start of simulation, the returned value from the
> > $past function is a value of X.
> > 
> > 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
> > 
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