Re: [sv-ac] RE: New version of 3213 uploaded

Dmitry,
Thinking this problem out, consider your example in a checker:
// Assume that we have this outside the checker
sequence req_seq;
  @ (posedge clk) request;
endsequence

// We then pass to a checker the argument *req_seq*
// In the checker:
let req = req_seq.triggered;
assert property(@ (posedge clk) $stable( req ) |-> go;

// Questions: In which region is $stable(req) (or *$stable*(*
req_seq.triggered*) ) evaluated in the assertion?
// req_seq.triggered and the assertion are evaluated in the
Observed region.

[3213] *A value change function detects a change (or, in the case of
$stable, lack of change) in the sampled value of an expression. The change
(or lack of change) is determined by comparing the sampled value of the
expression with the sampled value of the expression from the Postponed
region of the most recent strictly prior time step in which the clocking
event occurred.*
*
*
*[Ben] So when is the sampled value of req_seq.triggered? All in the
Observed region? Also, would $stable(request) be the same as
$stable(req_seq.triggered)?*
*request is sampled @ (posedge clk). *
*req_seq.triggered sampled at ? *
*what about **$stable(req_seq.triggered, posedge clk ). *
*If in a checker with an event, wouldn't *
* $stable(req_seq.triggered) be same as *
* $stable(req_seq.triggered, event)? // or the default clocking? *
*
*
*Ben *

On Mon, May 23, 2011 at 1:10 AM, Korchemny, Dmitry <
dmitry.korchemny@intel.com> wrote:

> Hi Ben,
>
>
>
> I don’t think that $stable(s.triggered) is useful per se, but it is useful
> when you pass it as an argument to a checker, especially when you write a
> library checker. Consider an example when a checker gets a request and a
> grant as its arguments and does some checking. E.g., it may check that the
> request should remain stable during several cycles. The corresponding actual
> argument may be a Boolean or a sequence. Therefore inside a checker we will
> have something similar to:
>
>
>
> let req = req_seq.triggered;
>
>
>
> and later
>
>
>
> assert property (…$stable(req)…);
>
>
>
> Regards,
>
> Dmitry
>
>
>
> *From:* ben cohen [mailto:hdlcohen@gmail.com]
> *Sent:* Friday, May 20, 2011 06:47
> *To:* Eduard Cerny
> *Cc:* Korchemny, Dmitry; sv-ac@eda-stds.org
> *Subject:* Re: [sv-ac] RE: New version of 3213 uploaded
>
>
>
> ..16.9.3: $stable(s.triggered) will change value depending whether it is
> called in the active or observed region. Is it not a race between the
> update of s.triggered and the use of it? Should there be a sentence that
> says something about ordering the evaluations?
>
>
>
> Ed,
>
> Good point. What's you're saying can be shown in this example (for
> discussion purposes)
>
> always begin : testcase1
>
> wait (s1.triggerred);
>
> *// Now in Observed region *
>
> x=$stable(s.triggered);
>
> end
>
>
>
> always begin : testcase2
>
> @ (posedge clk)
>
> *// Now in active region *
>
> x=$stable(s.triggered);
>
> end
>
>
>
> LRM changes:
>
> The situation is different when the argument of $stable is s.triggered,
> where s is a named sequence. The sampled value of s.triggered is its current
> value, and $stable(s.triggered) compares the current value of
> $stable(s.triggered)with its value from the Postponed region of the previous
> clock tick.
>
> In testcase, current value ==1
>
> In testcase2, current value==0
>
> Question: Is $stable(s.triggered) useful?
>
> Ben
>
>
>
> *From:* owner-sv-ac@eda.org [mailto:owner-sv-ac@eda.org] *On Behalf Of *Korchemny,
> Dmitry
> *Sent:* Thursday, May 19, 2011 10:41 AM
> *To:* 'sv-ac@eda-stds.org'
> *Subject:* [sv-ac] New version of 3213 uploaded
>
>
>
> Hi all,
>
>
>
> I uploaded the new version of 3213
> http://www.eda-stds.org/mantis/file_download.php?file_id=5053&type=bugfollowing Scott’s and Anupam’s comments.
>
>
>
> Thanks,
>
> Dmitry
>
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