[ibis-macro] Re: Making IBIS responsive to the modeling needs of the industry ... new keyword [Specification]
- From: "Walter Katz" <wkatz@xxxxxxxxxx>
- To: <Arpad_Muranyi@xxxxxxxxxx>, "'IBIS-ATM'" <ibis-macro@xxxxxxxxxxxxx>
- Date: Tue, 2 Dec 2008 20:00:16 -0500
Arpad,
We passed around Cape Horne yesterday, and visited the Falkland Islands
(Malvenas) today. Seas surprisingly calm.
I understand your point, but right now IBIS is not being responsive to the
needs of the industry. If we could find a way to quickly implement things
like derating, masks, . then this idea would not make sense. But DDR2
derating has been around for 4 years and USB masks have been around for
close to that and IBIS has not been responsive.
For example, SiSoft has implemented all of the DDR2, DDR3 and DDR FB design
rules using |SiSoft IBIS keywords that meet JEDEC DDR rules. For each new
part that has a DDR compliant bus our customers need to include these
|SiSoft records. I expect that Mentor, Cadence, Agilent, Zuken, . have done
something similar. Each of us has implemented these DDR rules in our own
way. By having records such as "[Specification] DDR2_667_CLKIN" SiSoft can
point to our own private "Include" file that has these DDR rules as we have
implemented them. Other EDA companies can point to their own "Include" files
that implement this specification. As new requirements get specified by
Industry Standards Groups such as JEDEC, all IC vendors need to do is have a
standard way of having a Model point to an industry standard, and this is
what I am proposing.
Just look at the confusion we have created by the IBIS implementation of
VinH_AC, which kind-of satisfies the JEDEC measurement rules but in fact
does not because it handles slow and fast corners differently then the JEDEC
spec. (IBIS specifies a typ value and then uses a threshold sensitivity to
adjust for voltage corners, JEDEC specifies values for each of the corners).
I think the IBIS method could make more sense, but customers require that
their designs satisfy the JEDEC spec.
"[Specification]" is one way we can make IBIS responsive to the needs of the
IC/EDA/Customer community.
Does anyone have another approach to solve this problem?
Do we want to solve this problem?
Walter
-----Original Message-----
From: ibis-macro-bounce@xxxxxxxxxxxxx
[mailto:ibis-macro-bounce@xxxxxxxxxxxxx] On Behalf Of Muranyi, Arpad
Sent: Tuesday, December 02, 2008 1:49 PM
To: IBIS-ATM
Subject: [ibis-macro] Re: Making IBIS responsive to the modeling needs of
the industry ... new keyword [Specification]
Walter,
In general, this [Specification] proposal looks very much like
IBIS-AMI, adding one simple keyword to IBIS and do the rest outside.
In the case of AMI, we wrote a whole new specification to describe
what AMI actually is, describing parameters, the format of the
parameter files, etc... I feel we will need to do the same in
this case too. Otherwise how would a tool know how to parse the
content of the file that [Specification] points to.
So while this seems to be an easy fix in the IBIS specification,
I don't see any reduction of work, because somewhere it must be
defined what the file contains and what its syntax is. Or did I
miss something?
Another topic: This proposal is yet another example, where we are
diverting things from the IBIS specification to some other, external
file or specification. If we keep this trend up, there will be
nothing left in IBIS itself, except a bunch of pointers. This
makes me wonder again about the conversation we are doing on the
overhauling of IBIS... Any comments?
Thanks,
Arpad
=====================================================================
_____
From: ibis-macro-bounce@xxxxxxxxxxxxx
[mailto:ibis-macro-bounce@xxxxxxxxxxxxx] On Behalf Of Walter Katz
Sent: Tuesday, December 02, 2008 12:22 PM
To: 'IBIS-ATM'
Subject: [ibis-macro] Making IBIS responsive to the modeling needs of the
industry ... new keyword [Specification]
All,
I do not expect to be able to attend an ATM meeting until Dec 15. I read
last weeks minutes and cam up with an idea that might solve many of the
issues that we have been suffering through:
We are all aware of the difficulty of introducing new features to IBIS (e.g.
C_Comp, Derating, Masks, USB rules, JEDEC rules, On Die S-parameters, LTI
Differential Tx and Rx models, .).
I would like to propose a simple solution that I think will solve this
problem by introducing a single new keyword to IBIS "[Specification]". The
format of a [Specification] record is simply:
[Specification] specification_name
[Specification] records can occur in the [Component] section, or [Model]
section. Each component and each model may have multiple [Specification]
records.
A specification_name can either be registered. It is registered by being
placed in an IBIS maintained registry of registered names along with a
specification_name.txt or specification_name.pdf document describing the
specification. If a specification_name is not registered, then the
specification_name.txt or specification_name.pdf needs to be supplied along
with the IBIS file.
I think the following example will explain the usefulness of this concept.
Consider a 667 MegHz, DDR2 memory part with the following models: CLKIN,
ADDCMD, DQ, DQS. The IBIS file might be:
[Model] CLKIN
[Specification] DDR2_667_CLKIN
[Model] ADDCMD
[Specification] DDR2_667_ ADDCMD
[Model] DQ
[Specification] DDR2_667_DQ
[Model] DQS
[Specification] DDR2_667_DQS_diff
The IBIS registry would contain the following entries for DDR2 667MegHz.
There would be other entries for other speed grades, DDR3, DDR4, .
DDR2_667_CLKIN DDR2_667_CLKIN.txt
DDR2_667_ ADDCMD DDR2_667_ ADDCMD.txt
DDR2_667_DQ DDR2_667_DQ.txt
DDR2_667_DQS_diff DDR2_667_DQS_diff.txt
DDR2_667_CLKIN.txt might contain
JEDEC Standard No. 79-2C
Speed grade 667MegHz
Signal CK
This is sufficient information for an EDA tool to create a design kit for
this model. It will be up to the EDA tool to determine how it implements
this in its environment.
Similarly there can be [Specification] for eye masks, on die s-parameters,
"ladder C_comp", . EDA tool vendors can implement solutions to each of these
problems in an appropriate way based on their target market and their tool
capabilities. The key point is that [Specification] allows IC vendors to
document in their IBIS [Model]s the measurement/simulation requirements of
their models without waiting for IBIS to come up with new
keywords/parameters, and allows EDA vendors to address industry standard
measurement rules in a timely manor.
USB, JEDEC, and other industry standard specifications fit naturally into
this scheme. Fancy C_Comp solutions can be more problematic, since the
[Specification] might be ties to a specific simulation methodology or EDA
tool, but it would at least document the solution used by the IC vendor for
their analysis. I would expect that IC vendors will learn to write these
[Specifications] in a way that would be supported by the EDA tools that
their customers use.
Walter Katz
Chief Scientist
Signal Integrity Software, Inc.
wkatz@xxxxxxxxxx
303.449-2308
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