RE: [vhdl-200x], vital issues

Subject: RE: [vhdl-200x], vital issues
From: John Shields (
Date: Wed Mar 12 2003 - 15:22:33 PST

I think it is defining language interoperability
that is desirable so that mixed language designs have standard
semantics. Verilog can and should keep the gate-level modeling
domain. It is a speed issue and an economic issue to maintain
duplicate gate level libraries.

The # of licenses issue is a business issue, but the interoperability
problem has been explored and mostly solved (albeit with proprietary
solutions). Perhaps one of the vendors can propose a standard
for interoperability to Accellera? This is not really
just a 200x or 1364 issue, which is what will make it difficult to

Regards, John

-----Original Message-----
From: []On Behalf
Of Rob Anderson
Sent: Friday, March 07, 2003 1:57 AM
Subject: Re: [vhdl-200x], vital issues

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?)


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
>> '

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