Subject: RE: [vhdl-200x], vital issues
From: Lance Thompson (lancet@us.ibm.com)
Date: Fri Mar 07 2003 - 06:22:31 PST
I think the point is that we are looking to standardize the VHDL/Verilog
interaction at this level. I'm glad to see that we are moving from saying
"read verilog netlists." I think the whole point of the requirement was to
be able to instantiate design units that may be implemented in vhdl or
verilog. One scenario that this allows is for a foundary to provide a
technology library in a verilog representation while the chip design is
done VHDL. True, current simulators allow this happen, but it not a
standard behavior.
Lance
"Jayaram
Bhasker" To: "Jim Lewis" <Jim@synthworks.com>, <vhdl-200x@eda.org>
<JBhasker@eSilico cc:
n.com> Subject: RE: [vhdl-200x], vital issues
Sent by:
owner-vhdl-200x@e
da.org
03/07/2003 07:58
AM
Jim:
>> What I want is the library elements in the VHDL netlist be
>> able to use Verilog library components and primitives.
I already do that today in verifying my designs. My simulator allows this
today, as
I am sure other mixed language simulators also do.
Maybe what you are looking for is this feature to be explicitly stated in
the standard?
With two of the simulators that I use, as long as the verilog models are
compiled into work,
I have no problem linking them in. So the question is, can I compile
verilog models into a
vhdl library called VLIB and use "use VLIB.all;" to link the models during
elaboration? Jim, I guess
this is what you are looking for, right?
- bhasker
------
J. Bhasker, eSilicon Corp
1605 N. Cedar Crest Blvd, Ste 615, Allentown, PA 18104
jbhasker@esilicon.com, 610.439.6831, 610.770.9634(fax)
-----Original Message-----
From: Jim Lewis [mailto:Jim@synthworks.com]
Sent: Thursday, March 06, 2003 10:54 PM
To: vhdl-200x@server.eda.org
Cc: Jim Lewis
Subject: Re: [vhdl-200x], vital issues
I think I sent that too quick. What I want is speed
that is at least the same as Verilog.
What I was thinking of when I said netlist was library.
I am ok with having a VHDL netlist of gate library elements.
What I want is the library elements in the VHDL netlist be
able to use Verilog library components and primitives.
Again one library format common to both languages would
have great benefits for all.
Cheers,
Jim
Jim Lewis wrote:
> If we were to develop a new library solution, someone
> would have to spend money to develop sign-off quality
> vendor libraries. In the current economy, do they have
> money to support two different netlist formats for
> sign-off quality libraries?
>
> The current VHDL gate level libraries are slow.
> According to a presentation at DVCon, Verilog
> gate-level libraries are 4X faster than VHDL libraries.
>
> If we can read and execute Verilog gate-level libraries, I
> get the speed I want, without having to pay for two licenses
> to run one simulation. Vendors (EDA and silicon) get the
> advantage of only having to support one library format.
>
> I suppose if you could give me a library format that would
> simulate faster than Verilog gates, I might be interested.
>
> Cheers,
> Jim
>
>
>> Actually the VHDL netlist is not as much as a problem as the
>> VHDL gate models. It would be nice to have precompiled libraries,
>> whether they came from Verilog or whatever is not of "vital"
>> importance. I'd be glad to see less of vital models, they do
>> not show VHDL in a good light.
>>
>> The netlist itself does not lead to inefficiencies, it contains
>> no models, just connectivity. I don't see savings to be gained
>> by reading in a Verilog netlist over a VHDL netlist.
>>
>> There are still of course problems reading netlists, mostly
>> environmental, library related since the netlist is multi-use.
>> Not clear things are better in Verilog.
>>
>> The SDF is the same regardless, excepting of course that VHDL
>> "out" ports cannot be read so one has to artificially inflate
>> the design before the VHDL and Verilog netlist signals can have the
>> same names. (this issue is on our list) This would be a real
>> headache if you tried to read a Verilog netlist into VHDL.
>>
>> It is worth noting the trend is away from having setup-hold, skew,
>> etc. checked in the models. These things are checked in the STA,
>> where there is more information than the SDF has. For simulation,
>> there is more interest in fast models. So we could have simpler
>> VHDL gate models for simulation, if there was any incentive for
>> the simulation people to supply them (did you ever see software
>> get smaller?)
>>
>> --Rob
>>
>> Jim Lewis wrote:
>>
>>> Francoise,
>>> I see there being two aspects to this.
>>>
>>> 1) Read Verilog Gate-level Netlists
>>> Vital is not enjoying the wide support we wished for.
>>> Vital is also slow compared to Verilog gate-level netlists.
>>> If Vital died, silicon vendors would only need to support
>>> one gate-level library format. EDA vendors would no longer
>>> need to support Vital. Hence, this would be good for both.
>>>
>>> However, the current situation is not good for VHDL designers,
>>> because to use a VHDL testbench with a Verilog gate-level
>>> netlist will cost me two licenses, one for VHDL and one
>>> for Verilog. Note for a Verilog designer it would only
>>> cost one license.
>>>
>>> To benefit both users and vendors, it would be best if
>>> Verilog gate-level netlists were included as part of the
>>> langauge.
>>>
>>> 2) Standardized Verilog Interface
>>> Standardize how to connect a Verilog design to VHDL.
>>> This would take us away from a Vendor specific
>>> implementation (which at the current time may or may not
>>> be identical, but it would be nice if it were documented
>>> somewhere in the standard).
>>>
>>> This of course should and will likely cost two licenses.
>>>
>>> Cheers,
>>> Jim
>>>
>>> Francoise Martinolle wrote:
>>>
>>>> I noticed in the priority spreadsheet that a few people (Jim Lewis,
>>>> Williams and Bishop)
>>>> have voted for read and simulate Verilog netlists.
>>>> I was wondering of one of them could provide a short description of
>>>> this request.
>>>>
>>>> thanks
>>>> Francoise
>>>
>
>
-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Jim Lewis Director of Training mailto:Jim@SynthWorks.com SynthWorks Design Inc. http://www.SynthWorks.com 1-503-590-4787Expert VHDL Training for Hardware Design and Verification ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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