Subject: Re: [sv-ec] Re: [sv-bc] SystemVerilog 3.1 Scheduling Semantics
From: Arturo Salz (Arturo.Salz@synopsys.com)
Date: Wed Feb 26 2003 - 13:06:04 PST
Francoise is absolutely right. There are several ambiguously defined PLI calls, and at this point we cannot and should not attempt to define those calls. Only for the purpose of illustrating, we may want to show the various points at which implementations are calling tf_synchronize and cbRWsynch. But, those calls will continue to be ambiguous and different among implementations. However, as we move forward, we should very clearly define where the new callbacks occur so that users don't find themselves in the same quandary.
Arturo
----- Original Message -----
From: Francoise Martinolle
To: David W. Smith ; sv-ec@eda.org ; sv-ac@eda.org ; sv-cc@eda.org ; sv-bc@eda.org
Sent: Tuesday, February 25, 2003 1:17 PM
Subject: [sv-ec] Re: [sv-bc] SystemVerilog 3.1 Scheduling Semantics
David,
I don't know what is the reflector for the scheduling semantics committee so I am sending my
comments to this reflector. Please forward to whom it should be sent to.
I read the proposal and I noticed some errors in the PLI callback mappings.
In the figure 5.1, the posponed region should be an oval to specify that only PLI callbacks
are supposed to occur in that time slot, unless we are providing a new Verilog construct which creates postponed process (like VHDL) and which would execute just before the simulator moves to its next time queue.
It is worth while to note that the time slots in which the tf_synchronize and cbRWsynch callbacks occur are not clearly defined in 1364, and is not implemented the same way between VXL, NC, VCS and modelsim simulators. This was the object of the paper at the last DVCON: "The facts and fallacies of Verilog event scheduling: is the IEEE 1364 Standard Right or Wrong?"
This behaviour of these callbacks has been left as is and will not be modified so that
applications will not break because of a change of behaviour. However two new callbacks
were created for which the time slot occurrence is unambiguously defined:
cbNBASynch
is guaranteed to occur pre NBA and before any cbRWSynch callback
(whenever they happen)
cbAtEndOfSimTime
is guaranteed to occur post NBA and after cbRWSynch (whenever they happen)
I think we should leave tf_synchronize and cbRWSynch out of the mapping table since
they can be mapped to different PLI regions, or mark the various interpretations of these
callbacks.
cbRoSynch and tf_rosynchronize should be mapped to the posponed PLI region.
Are there any new callbacks defined for the post-observed region?
For completion, you need to add the tf_(i)setdelay, tf_(i)setlongdelay and tf_(i)setrealdelay,
vcl callbacks, tf_asynchon, etc...
Francoise
'
At 04:55 PM 2/24/2003 -0800, David W. Smith wrote:
The attached document was created and reviewed by the Scheduling Semantics Working Group. This group was formed from each of the SV committees to review the scheduling semantics required in SystemVerilog to support the enhancements being made by each of the committees. The members of the group are:
Bassam Tabbara (Novas) (SV-AC)
Dennis Brophy (Model Tech/Mentor) (SV-BC)
Faisal Haque (Cisco) (SV-AC)
Jay Lawrence (Cadence) (SV-EC)
Joao Geada (SV-CC)
Matt Maidment (Intel) (SV-BC)
Michael Rohleder (Motorola) (SV-CC)
Neil Korpusik (Sun) (SV-EC)
and Phil Moorby, Arturo Salz, and Peter Flake from Synopsys representing the original definition. There were 9 votes in total (one for each committee representative and 1 for the trio representing the original definition).
Cliff Cummings (Sunburst-Design), Tej Singh (Model Tech/Mentor), and Mehdi Mohtashemi (Synopsys) also attended some of the meetings and participated in the discussions.
The result of this working group was the unanimous (one member abstained due to time conflicts with work limiting his ability to evaluate the work).
In addition to the attached document there will be a presentation on Friday (being crafted by Arturo Salz and Jay Lawrence) that covers the technical content and rationale for the document.
Regards
David
David W. Smith
Synopsys Scientist
Synopsys, Inc.
Synopsys Technology Park
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Hillsboro, OR 97124
Voice: 503.547.6467
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FAX: 503.547.6906
Email: david.smith@synopsys.com
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