[ibis-macro] Re: Truth table taken to the next level

  • From: "Todd Westerhoff" <twesterh@xxxxxxxxxx>
  • To: <ibis-macro@xxxxxxxxxxxxx>
  • Date: Wed, 28 Apr 2010 14:06:55 -0400 (EDT)



I couldn't disagree with you more, but then you already knew that.


This effort isn't EDA-centric at all, and never was, in my opinion.  The
focus has always been squarely on allowing the systems designer to use
IBIS-AMI models and simulation tools to make critical design decisions.
Statistical simulation lets users run many simulations quickly to identify
which cases have the best chance of success.  Time-domain simulation
provides the detailed modeling of adaptive equalization and clock recovery
needed to sign-off a design into manufacturing.  That's been the vision
since late 2006.


IBIS-AMI has always supported both simulation modes.  The first reference
model and toolkit SiSoft released in August 2007 demonstrated how Init and
Getwave can perform the equalization needed to support both Statistical
and Time-Domain simulation.


Multiple semiconductor vendors have already released IBIS-AMI models that
support both Statistical and Time-Domain simulation (Init_Returns_Impulse
= True, Getwave_Exists = True, Use_Init_Output = False) and the systems
companies we're working with are asking their semiconductor suppliers to
release more.  Those same systems companies are asking semiconductor
companies whose IBIS-AMI models don't support both simulation modes to
upgrade their models.  The system designers clearly see the benefit.


Commercial models and EDA tools that support both simulation modes have
been in the marketplace for over 2 years.  This discussion is about
properly documenting the capabilities and flows that already exist, not
going back to a "simpler flow".  Customers simply aren't going to abandon
capabilities they find useful and productive.


Scott was absolutely right; model makers want flexibility in creating a
model and documenting how it should be used, and the simulator control
parameters we've been discussing give them exactly that capability.


The questions you've listed below amount to a model maker asking for
guidance as to how they should best represent their IP's equalization and
clock recovery behavior.  There's no doubt that we can provide clear
guidance to that model maker for the flows we've been discussing.





Todd Westerhoff
VP, Software Products
6 Clock Tower Place, Suite 250
Maynard, MA 01754
(978) 461-0449 x24


From: ibis-macro-bounce@xxxxxxxxxxxxx
[mailto:ibis-macro-bounce@xxxxxxxxxxxxx] On Behalf Of Ken Willis
Sent: Wednesday, April 28, 2010 11:09 AM
To: ibis-macro@xxxxxxxxxxxxx
Subject: [ibis-macro] Re: Truth table taken to the next level


Hi Arpad,


My apologies for missing the meeting yesterday, I just returned from
vacation and was digging out.


I am concerned that we are going in entirely the wrong direction with
this, in that it is becoming far too EDA-centric and not IP
supplier-centric enough. And I think the latter is what we need to focus
on if we are ever to have a robust pool of Serdes models available for the
SI engineering community to use.


I have spoken with a lot of Serdes IP suppliers, and have never heard any
mention of supporting statistical or LTI TD or non-LTI TD or partial
statistical or full non-LTI TD or any other specific kind of analysis.
What I hear is things much more like this:


- What IBIS-AMI API do I need to use for my Serdes Tx / Rx? I want to use
the most straightforward approach to model my filter.

- Does the filtering in my Serdes IO do a one-time adaptation to my
channel? If it does I will use the modified impulse response approach,
since that is simplest.

- Does my filtering do real-time dynamic kind of adaptation? If it does, I
will need to use the GetWave approach and process waveforms directly.


This is admittedly a little over-simplified, but I think is basically on
target. I think we would do much better to think more along these lines
rather than add all the complexity I see in these tables below. To be
successful, I think we need to keep this as simple as possible, and enable
models to be developed. I would even go as far as to say that the most
practical approach for a given Serdes IO would be to use either the
impulse response or GetWave API, but not both together.


I would be interested to hear opinions on these ideas from the people on
this list.




Ken Willis

Sigrity, Inc.





From: ibis-macro-bounce@xxxxxxxxxxxxx
[mailto:ibis-macro-bounce@xxxxxxxxxxxxx] On Behalf Of Muranyi, Arpad
Sent: Wednesday, April 28, 2010 1:57 AM
To: ibis-macro@xxxxxxxxxxxxx
Subject: [ibis-macro] Truth table taken to the next level


Dear AMI experts, 
I cleaned up the spreadsheet with the truth table that we discussed 
in our ATM meeting today.  It looks like this now: 

Picture (Device Independent Bitmap)

I hope I got it right this time. 

The next thing I would like to do is to extend this table 
and spell out how these conditions can be applied to Tx 
and Rx independently.  In other words, I don't believe 
that our intent was to require these Booleans to be the 
same for both Tx and Rx.  But how many combinations are 

We have four (4) combinations per buffer, and we have two 
buffers, which could theoretically allow 4^2 = 16 total 
possibilities.  Are they all valid? 

Picture (Device Independent Bitmap)



JPEG image

JPEG image

Other related posts: