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

Hi Ben,

Please, see below.

Thanks,
Dmitry

From: ben cohen [mailto:hdlcohen@gmail.com]
Sent: Monday, May 23, 2011 12:27
To: Korchemny, Dmitry
Cc: Eduard Cerny; sv-ac@eda-stds.org
Subject: 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?
[Korchemny, Dmitry] Its sampled value is its current value. It depends where you call it.

All in the Observed region? Also, would $stable(request) be the same as $stable(req_seq.triggered)?
[Korchemny, Dmitry] What is request?

request is sampled @ (posedge clk).
req_seq.triggered sampled at ?
[Korchemny, Dmitry] at the time it is called.
what about $stable(req_seq.triggered, posedge clk ).
[Korchemny, Dmitry] ?
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?
[Korchemny, Dmitry] What is a checker with an event?
Ben

On Mon, May 23, 2011 at 1:10 AM, Korchemny, Dmitry <dmitry.korchemny@intel.com<mailto: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<mailto:hdlcohen@gmail.com>]
Sent: Friday, May 20, 2011 06:47
To: Eduard Cerny
Cc: Korchemny, Dmitry; sv-ac@eda-stds.org<mailto: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> [mailto: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<mailto: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=bug following Scott's and Anupam's comments.

Thanks,
Dmitry
---------------------------------------------------------------------
Intel Israel (74) Limited

This e-mail and any attachments may contain confidential material for
the sole use of the intended recipient(s). Any review or distribution
by others is strictly prohibited. If you are not the intended
recipient, please contact the sender and delete all copies.

--
This message has been scanned for viruses and
dangerous content by MailScanner<http://www.mailscanner.info/>, and is
believed to be clean.
--
This message has been scanned for viruses and
dangerous content by MailScanner<http://www.mailscanner.info/>, and is
believed to be clean.
---------------------------------------------------------------------
Intel Israel (74) Limited
This e-mail and any attachments may contain confidential material for
the sole use of the intended recipient(s). Any review or distribution
by others is strictly prohibited. If you are not the intended
recipient, please contact the sender and delete all copies.
---------------------------------------------------------------------
Intel Israel (74) Limited
This e-mail and any attachments may contain confidential material for
the sole use of the intended recipient(s). Any review or distribution
by others is strictly prohibited. If you are not the intended
recipient, please contact the sender and delete all copies.
-- 
This message has been scanned for viruses and
dangerous content by MailScanner, and is
believed to be clean.