actually my thinking is somewhat at varience. 1. I believe that the most attractive language is one which should include powerful but minimal set of syntax. From my limited knowledge of ams I tend to view it as unduly complex for the task. I am concerned that it will actually stand in the way of compact modeling and slow down real advnaces. I fear of "natural" tendency to bloat the models with all kinds of unnecessary overheads as in the inclusion of logic preprocessing circuits. 2. Spice is actually a very powerful language precisely because of its limited constructs. It provides connectivity information in the most basic, abstract but elegant manner. That is why it is not a huge task to go from a circuit schematic to a spice description 3. The following fundamental additons will make it unbeatable. a. arbitrary locally defined parameters and parameter passing - many commercial simulators already have this b. generalized equation element of the form f(v,i, .....parametrs) = 0; where v and i are voltage and current vectors. all the spice elements including EFGH are a variation of this general variety. 4. as we go into an era with even more serious analog models (read network equation with node conservation which spice is all about), I will be loathe to take on another curve ball, which pretends to be high level but not really but at the same time too complex for network description. Such a development can only obscure and deflect from real advances. --- "Muranyi, Arpad" <arpad.muranyi@xxxxxxxxx> wrote: > Todd, and all, > > Excellent summary! In fact this is the best > description I > have seen so far for the fundamental problem we have > in IBIS. > > "Both the building blocks AND > the structure are pre-defined." > > The good news is that we did recognize this problem > and > acted on it. That's why we have IBIS4.1 now. With > the > new keywords [External Circuit], [Circuit Call] and > [Node > Declarations] we can basically instantiate and > define > building blocks and build structures as needed. > > The problem I see now is that being so new it will > take > some time before these capabilities will be widely > used > and supported by tool vendors. And Chris' thread > and > Don's proposal makes us painfully aware of the need, > RIGHT NOW. So what should we do? > > Don's macromodeling proposal is an attempt to bridge > over > this time gap for the immediate future. I can't > help, but > I have some concerns. Readers, please feel free to > comment, > or contradict on any of these points, because I am > also > looking for answers as I am writing this. > > 1) The faster the macromodeling proposal is > attempted to be > realized, the fewer features it will define. > (Remember, the > EFGH elements have a very wide variety of syntax > features, at > least in HSPICE). How useful is it going to be with > a limited > set of capabilities? We already had a similar > experience > when we worked on the IBIS-X (Al Davis SPICE) > proposal. > > 2) On the other hand, if more features are > implemented, it > may take too long to finish the specification for it > to be > useful in the time frame it was intended to help. > > 3) If (and that is a big IF) we succeed in this > step towards > basically standardizing some SPICE features, no > matter how small > this first step is, I am pretty sure that there will > be a flood > of requests towards standardizing the rest of SPICE. > This in > itself may not be a bad idea if it were not for the > same > limitations I mentioned in the thread Chris started. > (SPICE > has the same problem as IBIS when it comes to adding > new models > and equations to its primitives, they are all > pre-defined, using > Todd's words). Of course, I have yet to see how the > various SPICE > vendors would react to the idea of standardizing > SPICE. > > 4) I am a fan of the AMS languages because it > solves the problems > of IBIS as well as SPICE. Also, it can be used as > if it was SPICE, > BUT IT CAN DO A LOT MORE. Because of that, I feel > that ultimately > AMS will be the choice of modeling language in the > long run. > However, I feel that Don's macromodeling proposal, > if it succeeds, > will slow down and delay the acceptance of the AMS > languages. Why > should we delay the inevitable? Why wouldn't we > want to help > it by promoting it? > > 5) I agree, there are immediate needs TODAY for > which AMS > solutions may not be available yet. However, as Don > pointed > out, Cadence has done this macromodeling for years > around their > IBIS2.1 primitive. It can also be done the same way > in HSPICE > around their B-element. I am pretty sure Mentor and > other > companies may have similar capabilities. Since > workarounds > are available, the real question in my mind is: how > much are > we benefiting by standardizing the workarounds? Is > it worth > spending the time and energy to make this an > official > specification while we could promote the acceptance > of AMS > using the same energy? > > 6) I have another idea! Based on Todd's definition > of what the > problem is with IBIS (pre-defined building blocks > and structure), > and the fact that we have a solution for that in the > new keywords > [External Circuit], [Circuit Call] and [Node > Declarations], why > don't we write a few AMS primitives, such as the > EFGH elements > and the B-element so that they could be macromodeled > together > any whichever way, using the above keywords? This > would provide > the same capability Don's proposal is suggesting > without having > to change the IBIS specification at all! I have > already posted > a B-element equivalent in VHDL-AMS on the IBIS web > site a long > time ago, a Verilog-AMS equivalent of it is also > available > (courtesy of Ron Vogelsong, Cadence) and I don't > think it would > take too much effort to write up the EFGH element > equivalents > in *-AMS either. (Any takers?) > > Arpad > =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= > =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= > =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D > > > -----Original Message----- > From: si-list-bounce@xxxxxxxxxxxxx > [mailto:si-list-bounce@xxxxxxxxxxxxx] = > On Behalf Of Todd Westerhoff (twesterh) > Sent: Thursday, March 24, 2005 8:48 AM > To: si-list@xxxxxxxxxxxxx > Subject: [SI-LIST] Macromodeling > > I'm weighing in a bit late here, but I'm hoping I'll > be able to = > underscore > the point Donald was trying to make with the > original use of the term > "macromodeling". > > Macromodeling to me, is nothing more than a syntax > that allows me to = > combine > pre-existing elements (which are behavioral in their > implementation) > arbitrarily. I can make whatever I want, as long as > I use the building > blocks I already have. > > The issue with IBIS is that we can't do that. Both > the building blocks = > AND > the structure are pre-defined. You have a few > opportunities to change > things, I grant you [Series Pin Map and such] ... > but the structures = > are, by > and large, pre-defined. > > Donald was making the case for adding some "building > blocks" (controlled > sources and such) to IBIS, and then allowing a > syntax that would allow = > those > building blocks to be combined freely by the model > maker. He offered up > that Cadence had implemented the B-element in the > SPECCTRAQuest = > simulation > engine years ago, and then handled each extension to > IBIS since then = > using > this macromodeling technique. > > Whether others agree or not - this makes good sense > to === message truncated === __________________________________ Do you Yahoo!? Yahoo! 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