Hi Gord, So I hesitate to make this change only because we would be hardwiring this example with an initial value when we really want the example to more broadly show what can happen at any point in time in the simulation. I'm sure it doesn't make any difference from an implementation perspective, but it just makes thing more understandable from a violation report perspective. This example is saying this violation glitch and recovery can happen at any point in time during simulation. I do agree that the assignment to "one" is superfluous so I will remove that: always_comb begin not_a = !a; end always_comb begin : a1 unique case (1'b1) a : z = b; not_a : z = c; endcase end In this example the unique-case is checking for overlap in the two case-item selects. When a first attains a new value of 1, this unique-case may be executed while a and not_a are both true, so the violation check for uniqueness will fail. But since this violation check is in the active region set the failure is not reported immediately. After the update to not_a, process a1 will be rescheduled, which results in a flush of the original error. After that, the violation check will pass, and no error will be reported. WRT to the clarification to the wording following "this unique-case may be executed" I didn't have any issues following it (remember I didn't initially write this) and kept the "may" assumption in mind as I read the rest of the paragraph. If you have any suggestion on how to clarify this further I welcome your inputs. All that said, I don't have too strong of an opinion about this so if you _really_ want the initializations in there and will vote no otherwise, I'll make your changes:') Thanks, -Tom >-----Original Message----- >From: owner-sv-bc@server.eda.org [mailto:owner-sv-bc@server.eda.org] On >Behalf Of Gordon Vreugdenhil >Sent: Thursday, February 14, 2008 2:38 PM >To: Maidment, Matthew R >Cc: sv-bc@server.eda.org >Subject: Re: [sv-bc] e-mail ballot due Monday, Feb 18, 8AM PST > > > >Maidment, Matthew R wrote: >> I already updated 1340. The other suggestions are fine. >> Here is the updated ballot: >> >> SVDB 1828 _X_Yes ___No >> http://www.eda.org/svdb/view.php?id=1828 > >> SVDB 2008 ___Yes _X_No >> http://www.eda.org/svdb/view.php?id=2008 > >The example in 12.5.3.1 is not very clear. The text >talks about "When a first attains the value 1...". It >would be better to have the example be slightly more >complete with respect to "a" and get rid of the immaterial >assignment to "one". I would have something like: > int a = 0; > int not_a = 1; > .... > always_comb begin : a1 > a = 1'b1; > unique case (one) > a : z = b; > not_a : z = c; > endcase > >This would make the text more directly correspond to a >simple reading of the example. > >12.4.2.1 is similar, but the assignment "one = 1'b1;" in >12.5.3.1 makes that example worse since one might think >that the assignment to "one" would be significant to the >discussion and it is not. > >I'll vote in favor of 2008 if the above change is made >or if some other clarification is made to the combination >of text and example. > > >The description in 12.5.3.1 following the example is Ok >since it says that "... this unique-case MAY be executed >while a and not_a are both true..." (emphasis added). The >text following that assumes that scenario and the wording >could perhaps make the assumption more clear. I won't >vote against based on that but wanted to note the wording >in case anyone else was more troubled by the current wording. > > >> SVDB 2219 _X_Yes ___No >> http://www.eda.org/svdb/view.php?id=2219 >> >> SVDB 2043 _X_Yes ___No >> http://www.eda.org/svdb/view.php?id=2043 >> >> SVDB 1564 _X_Yes ___No >> http://www.eda.org/svdb/view.php?id=1564 > > >Gord. > >-- >-------------------------------------------------------------------- >Gordon Vreugdenhil 503-685-0808 >Model Technology (Mentor Graphics) gordonv@model.com > > >-- >This message has been scanned for viruses and >dangerous content by MailScanner, and is >believed to be clean. -- This message has been scanned for viruses and dangerous content by MailScanner, and is believed to be clean.Received on Fri Feb 15 09:04:10 2008
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