[IBIS] RE: IBIS model of differential driver with programmable multi-tap preemphasis

From: Muranyi, Arpad <Arpad_Muranyi_at_.....>
Date: Thu Jul 23 2009 - 09:51:40 PDT
Nitin,

I do not know of any way to cascading models inside
an IBIS file the way you describe (output to the
input of the next buffer, etc...).  That wouldn't be
possible even if you added dummy pins to an IBIS model
and connecting one pin to the next pin externally
because the main thing in IBIS is that the core side
of the buffer (stimulus or output of the receiver) is
theoretically hidden from the user.

The only thing I can think of is the usage of External
Buffer or Circuit one way or another, but I didn't
think it through yet how exactly it could/should be
done if your case.  That would also depend on how you
would model your buffer with these keywords...  Have
you considered Verilog-A and these keywords yet as
an option?

Arpad
======================================================

-----Original Message-----
From: Nitin Kumar CHHABRA [mailto:nitin.chhabra@st.com] 
Sent: Thursday, July 23, 2009 12:28 AM
To: 'Lance Wang'; twesterh@sisoft.com; Muranyi, Arpad
Cc: ibis@server.eda.org; si-list@freelists.org; 'Nitin GUPTA'; 'Vishrant
GOYAL'
Subject: RE: IBIS model of differential driver with programmable
multi-tap preemphasis

Hi Arpad,
Thanks for your valuable input. 
You are right that I need the pure analog environment for simulation and
so
IBIS-AMI/IBIS-AMS were not taken in account.
Since Input pattern is also unknown I could not use driver-scheduling.
The example approach you gave is exactly what we had followed, only
difference being I used ELDO-2009 for stimulus generation in place of
HSPICE.
But still the relationship of those signals was outside IBIS world and
is
simulator dependent. We wanted to make IBIS model which could be used by
any
common simulator for analysis.

Inside the IBIS file only, is there any method to cascade different
models
i.e. output of one model becomes input to other and so on.

Hi Tod,
This is HDMI transmitter with multilevel tap-pre-emphasis , so IBIS-AMI
is
not good solution.


Hi lance,
I am still not sure how to use Driver scheduling in this case. The input
pattern could change and depending on that pattern the required
pre-emphasis
level could be activated. Depending on history of previous bits, the
particular level of tap is activated and pre-emphasis strength changes.
Could you please elaborate how to use driver scheduling in that case.
Spice macro-modeling is one of the best approaches for the same and
almost
same as what Arpad had explained in his example. 
 

Thanks and regards,
Nitin


-----Original Message-----
From: si-list-bounce@freelists.org [mailto:si-list-bounce@freelists.org]
On
Behalf Of Lance Wang
Sent: Wednesday, July 22, 2009 8:49 PM
To: ibis@server.eda.org; si-list@freelists.org
Subject: [SI-LIST] Re: [ibis-macro] IBIS model of drifferential driver
with
programmable multi-tap preemphasis

Nitin,
Additional to Arpad's comments:
There is a possibility to use Driver Schedule for multi-tap pre-emphasis
buffer modeling. I did a presentation in 2005 and showed it works for 4
tap
in the presentation below: (page 41)
http://www.vhdl.org/pub/ibis/summits/mar05j/wang.pdf

Also, you could do Spice-macromodeling with IBIS buffer models for
pre-emphasis. The benefits for it are faster and can be used in the most
of
Spice simulators. Users will not be requested to cost more for new
tools.

http://iometh.com/Product/SIMDE/Macromodeling.pdf
http://www.vhdl.org/pub/ibis/summits/oct06b/wang.pdf

Hope this helps,

Lance Wang
IO Methodology Inc.

SIMDET V1.0 - Signal Integrity Model Development Environment
The complete IBIS / Spice Macromodel generation and validation tool
www.iometh.com/Product/SIMDE



-----Original Message-----
From: si-list-bounce@freelists.org [mailto:si-list-bounce@freelists.org]
On
Behalf Of Muranyi, Arpad
Sent: Wednesday, July 22, 2009 10:54 AM
To: ibis@server.eda.org; si-list@freelists.org
Subject: [SI-LIST] Re: [ibis-macro] IBIS model of drifferential driver
with
programmable multi-tap preemphasis

Nitin,

If you have access to the stimulus, you could pull this off
with the Driver Schedule or even without it, but that would
be a semi official IBIS solution because it may not work in
all tools.  For example, if you do it with the HSPICE B-element,
you could make a B-element for each stage of your buffer,
and then make a special stimulus generator which reproduces 
the bit pattern dependent waveforms for the input to each
B-element (buffer stage).  This way the stages of your buffer
would still be IBIS models, but the relationship between them
would be outside the IBIS world.

Another way to do it would be to use the *-AMS extensions of
IBIS.  This way you could make a completely official model
for the entire buffer.  However, not all IBIS tools have
implemented the *-AMS extensions of IBIS, although there are
several tools with Verilog-A support which may be sufficient
for what you want to do.

I hope this helps.

Arpad
===============================================================

-----Original Message-----
From: ibis-macro-bounce@freelists.org
[mailto:ibis-macro-bounce@freelists.org] On Behalf Of Nitin Kumar
CHHABRA
Sent: Wednesday, July 22, 2009 7:14 AM
To: ibis@server.eda.org; si-list@freelists.org
Cc: vishrant.goyal@st.com; nitin.chhabra@st.com; nitin.gupta@st.com
Subject: [ibis-macro] IBIS model of drifferential driver with
programmable multi-tap preemphasis

Hi experts,

We want to develop  the IBIS model for a differential driver with pre 
emphasis .
The driver has three tap with programmable pre emphasis options.

Does anyone came across such IBIS or could provide some IDEA how to 
proceed for the same.
Using Driver Scheduling, we are able to make model for first tap pre 
emphasis  buffer.
But we cannot accommodate the second  and third tap  options as they 
require previous bit histories.

with regards,
Nitin
 



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Received on Thu Jul 23 09:53:35 2009

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