[ibis-macro] Re: Analog Buffer model - the User's viewpoint
- From: Feras Al-Hawari <feras@xxxxxxxxxxx>
- To: "wkatz@xxxxxxxxxx" <wkatz@xxxxxxxxxx>, Ambrish Varma <ambrishv@xxxxxxxxxxx>, "'IBIS-ATM'" <ibis-macro@xxxxxxxxxxxxx>
- Date: Sat, 21 Jan 2012 01:38:17 -0800
Todd and Walter,
We all seem to agree that S-parameters is the way to go to model proprietary
and more generic circuits. Therefore, we proposed BIRD 144 (that COMPLEMENTS
BIRD 116) to:
- Make referencing Tstone files much easier (i.e., without the need
for circuit wrapping). So why wrap it if it standard and it can be used
directly. As Ambrish said if you need to wrap your model, then you can use BIRD
116.
- Allow using Tstone with/without the AMI block as we allow
referencing it from either an External Model (if it represents an LTI Tx or
Rx) and/or External Circuit (if it represents RDL, ODT, package, etc)
- Allow referencing many Tstone files that correspond to many user
defined corners. This will allow the user to control the output swing and EQ
settings, for example, as suggested below
We are aware that user defined corners apply to other IBIS blocks, so our plan
was to introduce it in a simple way with respect to Tstone files. And then if
the IBIS committee likes the idea, our plan is to extend it to cover all the
applicable IBIS blocks in a separate BIRD.
Feras Al-Hawari
Cadence Design Systems
From: ibis-macro-bounce@xxxxxxxxxxxxx [mailto:ibis-macro-bounce@xxxxxxxxxxxxx]
On Behalf Of Walter Katz
Sent: Friday, January 20, 2012 5:58 PM
To: Ambrish Varma; 'IBIS-ATM'
Subject: [ibis-macro] Re: Analog Buffer model - the User's viewpoint
Ambrish,
BIRD 116 fully support Tstonefile as well, just limited to three corners.
Walter
From: ibis-macro-bounce@xxxxxxxxxxxxx [mailto:ibis-macro-bounce@xxxxxxxxxxxxx]
On Behalf Of Ambrish Varma
Sent: Friday, January 20, 2012 4:56 PM
To: 'IBIS-ATM'
Subject: [ibis-macro] Re: Analog Buffer model - the User's viewpoint
Todd,
We have discussed and compared BIRD 144 and Walter's approach multiple times
already. By your own opinion that you expressed in an earlier email (produced
below)
"For what it's worth, my personal opinion is that we'll end up with a standard
subcircuit that instantiates S-parameters in the long term. I suspect that
most device vendors won't be willing to describe their termination networks
with a clear text netlist, as it could expose details of their ESD and
compensation circuits they don't want to reveal. S-parameter blocks hide the
internal details, and I expect we'll see a standard template instantiating
TX/RX s-parameter data before too long."
you seem to understand the advantage of S-parameters. So in short, the
advantages of BIRD 144 (besides user defined corners) are that it supports non
IBIS-AMI simulations and easily allow S-Parameters to be instantiated (without
wrapping them in subcircuits). If there is a need for a subcircuit - then BIRD
116 should satisfy that.
Thanks,
Ambrish.
[cid:image002.gif@01CCD7F3.E8A25800]
Ambrish Varma | Member of Consulting Staff
P: 978.262.6431 www.cadence.com<http://www.cadence.com>
________________________________
From: ibis-macro-bounce@xxxxxxxxxxxxx<mailto:ibis-macro-bounce@xxxxxxxxxxxxx>
[mailto:ibis-macro-bounce@xxxxxxxxxxxxx]<mailto:[mailto:ibis-macro-bounce@xxxxxxxxxxxxx]>
On Behalf Of Todd Westerhoff
Sent: Friday, January 20, 2012 4:24 PM
To: 'IBIS-ATM'
Subject: [ibis-macro] Re: Analog Buffer model - the User's viewpoint
That doesn't make sense to me.
If we want to bypass the need to have a subcircuit (i.e. have a pre-defined
template) *AND* we want to have the ability to define the subcircuit where
needed, then we should just pursue BIRD 116 and pre-define a few templates.
That's exactly what Walter was suggesting. The only new thing I see in BIRD
144 is User Defined Corners, which are limited to Touchstone files only.
What's the added value here?
Todd.
--
Todd Westerhoff
VP, Software Products
SiSoft
6 Clock Tower Place, Suite 250
Maynard, MA 01754
(978) 461-0449 x24
twesterh@xxxxxxxxxx<mailto:twesterh@xxxxxxxxxx>
www.sisoft.com<http://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
From: ibis-macro-bounce@xxxxxxxxxxxxx<mailto:ibis-macro-bounce@xxxxxxxxxxxxx>
[mailto:ibis-macro-bounce@xxxxxxxxxxxxx]<mailto:[mailto:ibis-macro-bounce@xxxxxxxxxxxxx]>
On Behalf Of Ambrish Varma
Sent: Friday, January 20, 2012 4:17 PM
To: IBIS-ATM
Subject: [ibis-macro] Re: Analog Buffer model - the User's viewpoint
Todd,
We are not suggesting that BIRD 144 will replace BIRD 116. So if BIRD 116 &
dependency tables can fulfill your requirement, then great. Look at BIRD 144 as
a quick way of bypassing the requirement of having a subcct for the case when
the user wants to refer to a tstone file.
Hope I read your issue correctly.
Regards,
Ambrish.
[cid:image002.gif@01CCD7F3.E8A25800]
Ambrish Varma | Member of Consulting Staff
P: 978.262.6431 www.cadence.com<http://www.cadence.com>
________________________________
From: ibis-macro-bounce@xxxxxxxxxxxxx<mailto:ibis-macro-bounce@xxxxxxxxxxxxx>
[mailto:ibis-macro-bounce@xxxxxxxxxxxxx]<mailto:%5bmailto:ibis-macro-bounce@xxxxxxxxxxxxx%5d>
On Behalf Of Todd Westerhoff
Sent: Friday, January 20, 2012 4:03 PM
To: IBIS-ATM
Subject: [ibis-macro] Analog Buffer model - the User's viewpoint
All,
One of my colleagues here brought up a good point today - how the end-user
interacts with the model.
How do we expect that the user wants to interact with an IBIS-AMI model?
Specifically, how would they want to set up and run simulations? The answer,
in SiSoft's opinion, is to specify values for control parameters that
correspond as closely to the actual hardware as possible. Obviously a deep and
broad subject, of which I want to comment only on one small slice: how it
relates to analog modeling.
Let's assume we have a model where the output impedance (static impedance, as
Scott defined it) varies considerably depending on the TX output swing setting.
We expect that the user wants controls that lets them set the output swing and
EQ settings in a way where the mapping to hardware settings is obvious, with
the model/simulator figuring out to configure the details of the model.
Chances are, the analog model to be used will change as a function of the
output swing and EQ settings selected. If we're using subcircuit (as proposed
by BIRD 116) or Touchstone (as proposed by BIRD 144) methods, either the
equivalent circuit parameters (BIRD 116), or the Touchstone file selection
(BIRD 144) will have to change, depending on how the user sets the input
controls. I believe BIRD 116 & dependency tables can fulfill this requirement,
but I'm not sure that BIRD 144 (as currently proposed) can do this.
Todd.
--
Todd Westerhoff
VP, Software Products
SiSoft
6 Clock Tower Place, Suite 250
Maynard, MA 01754
(978) 461-0449 x24
twesterh@xxxxxxxxxx<mailto:twesterh@xxxxxxxxxx>
www.sisoft.com<http://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
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