[SI-LIST] Re: different flavor of AMI models ?
- From: "Todd Westerhoff" <twesterh@xxxxxxxxxx>
- To: "'si-list'" <si-list@xxxxxxxxxxxxx>
- Date: Tue, 07 Feb 2012 13:33:45 -0500 (EST)
Perry,
Good question, and a topic of confusion for many.
In your case, I suspect what's going on is that the vendor needs model
features that go beyond the published IBIS 5.0 spec to represent the
device accurately. There are lots of different reasons why, but most of
them boil down to one of two major categories:
1. Modeling jitter
While the IBIS 5.0 spec has provisions for modeling TX/RX jitter, there
are a number of things it can't do. For example, if you want to have a
different random jitter budget based on process corner, the published spec
has no provision for that. The good news here is that the IBIS-ATM
workgroup has agreed on proposed extensions to IBIS-AMI
(http://www.eda.org/pub/ibis/birds/bird123.2.txt) to support this. For
these extensions to become official, the proposal needs to be approved by
the IBIS Open Forum, at which time the extensions become slated for
inclusion in the next revision of the specification. Most EDA vendors
will start implementing support for extensions when a proposal is approved
by the Open Forum, although that's something you should confirm with your
vendor.
2. Improved analog modeling
One limitation of the current spec is that it doesn't really allow an
analog model to have output or input characteristics that vary with
frequency. At SerDes speeds, this can become a problem and some vendors
have adopted the practice of using S-parameter data in place of the analog
model. These models are commonly referred to as "on-die S-parameters".
On-die S-parameters and other extensions to analog modeling are discussed
in proposed BIRD 122 (http://www.eda.org/ibis/birds/bird122/bird122.pdf).
There are a much larger set of issues associated with analog modeling that
I won't get into here, because you don't need them to solve your problem.
Here's the deal:
Given that we (and by we, I mean SiSoft) occasionally have to work "beyond
the standard" to ensure accuracy in AMI models, we document the extensions
we use so that others know what to do with them. In your case, I expect
that the SiSoft .ami files will have Tstonefile, Voh and Vol parameters in
them, which you'll find documented in proposed IBIS BIRD 122
(http://www.eda.org/ibis/birds/bird122/bird122.pdf). I don't know what
the equivalent constructs are for the tool you use, but I expect that your
vendor will have a mechanism for dealing with them that can get you up and
running.
Improvements to analog modeling are still in the discussion stage, and I
expect that we'll see something different from proposed BIRD 122 in IBIS
5.2 ... but that doesn't change what you need to do today to get this
model running in your tool.
I hope that helps!
Todd.
--
Todd Westerhoff
VP, Software Products
SiSoft
6 Clock Tower Place, Suite 250
Maynard, MA 01754
(978) 461-0449 x24
twesterh@xxxxxxxxxx
www.sisoft.com
"It doesn't matter what you've heard
Impossible is not a word
It's just a reason
For someone not to try"
-Kutless
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]
On Behalf Of Qu, Pingyu (Perry)
Sent: Tuesday, February 07, 2012 12:21 PM
To: si-list
Subject: [SI-LIST] different flavor of AMI models ?
Hi,
I'm currently working with a vendor on an IBIS AMI model and they provided
two models, a Sisoft flavor and an ADS flavor. We have neither tool but we
have Hyperlynx, not sure which one I should try. Would like to understand
what makes the AMI model different for different tools ? I had an
impression that IBIS AMI is supposed to be a standard that works across
vendors ?
Regards
Perry
=======================================
Perry Qu
IPD Design & Qualification, Alcatel-Lucent Canada Inc.
600 March Road, Ottawa ON, K2K 2E6, Canada
Phone: 613-7846720 Fax: 613-5993642
Email: perry.qu@xxxxxxxxxxxxxxxxxx
=======================================
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