[SI-LIST] Re: IBIS-AMI Vendor Support Help
- From: Scott McMorrow <scott@xxxxxxxxxxxxx>
- To: Walter Katz <wkatz@xxxxxxxxxx>
- Date: Tue, 09 Feb 2010 11:19:02 -0500
See below:
Walter Katz wrote:
> All,
>
> On die S-Parameter is just one part of the problem. Models requiring on die
> S-Parameter are incompatible with the rest of IBIS IV and VT data, including
> things liked Vdiff, Cdiff.
>
I really hate statements without proof. Certainly "standard" IBIS
models with IV and VT tables could benefit from a frequency dependent
parasitic model.
> The problem with [External Circuit] it that it is explicitly outside of a
> model definition and therefore not model based. So if a chip had 300
> instances of the same SerDes differential model, then using [External
> Circuit] would require 300 instances of the same [External Circuit], this
> combined with IBIS inability to properly handle true differentials makes
> putting this capability in IBIS problematic.
>
There are several issues with this statement. Certainly an External
Circuit is model based. It is just not encapsulated in the same model
you are discussing. The use of 300 instances of the same External
Circuit is a red herring. This is just a matter of simulation model
management. By the same definition, 300 instances of the same SerDes
model are required. Finally, IBIS-AMI does not handle true
differential. All AMI algorithmic modeling has been decomposed to
differential mode only. This excludes any technique that might operate
on the two paths independently.
> As soon as the current revision of the AMI specification is completed,
> SiSoft will be introducing new AMI parameters that satisfy the Analog
> modeling requirements to support the AMI algorithmic modeling. One
> additional compelling reason to put this into the .ami file is that we have
> found that configuring the ami algorithmic model also configures the analog
> parasitics.
>
Why not introduce the new parameters into the discussion at this time?
> Walter
>
> Walter Katz
> 303.449-2308
> Mobile 720.333-1107
> wkatz@xxxxxxxxxx
> www.sisoft.com
>
> -----Original Message-----
> From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]On
> Behalf Of Muranyi, Arpad
> Sent: Tuesday, February 09, 2010 10:33 AM
> To: si-list@xxxxxxxxxxxxx
> Subject: [SI-LIST] Re: IBIS-AMI Vendor Support Help
>
> Ken,
>
> [External Model] may not work because it is specifically designed to
> replace the [Model] with a better modeling language content while
> preserving the same connectivity of the [Model] keyword. This means
> that the all of the nodes of [Model] or [External Model] are supposed
> to be connected the same exact way, which would prevent us to put die
> parasitics between the buffer model and the pads.
>
> However, [External Circuit] does not have this restriction, so we
> could potentially make use of that keyword for this purpose, perhaps
> referencing the new (proposed) IBIS-ISS capabilities which allow
> us to use S-parameters. If we went with this route, the question
> is, can we have a [Model] behind the [External Circuit], which is
> something I don't remember for sure now. I need to research the
> spec on that a little more...
>
> Arpad
> ========================================================================
>
> -----Original Message-----
> From: Ken Willis [mailto:kwillis@xxxxxxxxxxx]
> Sent: Tuesday, February 09, 2010 9:19 AM
> To: 'Todd Westerhoff'; Muranyi, Arpad
> Cc: si-list@xxxxxxxxxxxxx
> Subject: RE: [SI-LIST] Re: IBIS-AMI Vendor Support Help
>
> Hi Todd,
>
> On #1, it makes sense to incorporate S-parameters into IO models,
> especially
> since some major IP suppliers have this data today. I think the item
> that
> brings some uncertainty is why this would be pushed into the algorithmic
> (AMI) portion of the model, especially if new syntax/API has to be
> invented
> and supported. The intent of AMI was to capture the adaptive filtering
> behavior of these advanced Serdes devices, which you couldn't really
> model
> well in a circuit model. If the S-parameters are largely parasitic data,
> it
> seems more straightforward to include them in the analog circuit part of
> the
> model.
>
> I understand that there is no standard "IBIS" syntax for S-params right
> now,
> but I would agree with Arpad that Touchstone is widely supported. Maybe
> we
> should be looking at [External Model] > Touchstone or something like
> that.
> But we can continue the discussion in the IBIS forum.
>
> Thanks,
>
> Ken Willis
> Sigrity, Inc.
> 860-871-7070
> kwillis@xxxxxxxxxxx
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