[ibis-macro] Re: AMI-init should pass modified IR to getwave....
- From: "Todd Westerhoff" <twesterh@xxxxxxxxxx>
- To: <ibis-macro@xxxxxxxxxxxxx>
- Date: Thu, 14 Jun 2012 12:52:29 -0400 (EDT)
Taranjit,
Convolving the RDL IR with the channel IR will still not give you the
effects of reflections and ISI. You need to model the RDL properly and
include it the circuit analysis that derives the impulse response in the
first place. If you don’t, you’ve violated the fundamental premise that AMI
is based on.
I don’t see the point in discussing modeling approaches that don’t
accurately represent actual circuit physics.
Todd.
Description: cid:EAFF2D52-4B63-4A05-9D24-B96BE375B7E0@eau.wi.charter.com
Todd Westerhoff
VP, Software Products
Signal Integrity Software Inc. • <http://www.sisoft.com/> www.sisoft.com
6 Clock Tower Place • Suite 250 • Maynard, MA 01754
(978) 461-0449 x24 • <mailto:twesterh@xxxxxxxxxx> twesterh@xxxxxxxxxx
“I want to live like that ”
-Sidewalk Prophets
From: Taranjit Kukal [mailto:kukal@xxxxxxxxxxx]
Sent: Thursday, June 14, 2012 11:56 AM
To: 'twesterh@xxxxxxxxxx'; 'ibis-macro@xxxxxxxxxxxxx'
Subject: Re: [ibis-macro] Re: AMI-init should pass modified IR to
getwave....
Hi Todd,
That is why RDL IR is to be convoluted with channel to get overall IR. And I
would have loved to pass this to EDA tool that provides me resultant wave in
getwave for further processing (as against doing my own sampling and
convolution in getwave)
Somehow, it is not very convincing that we take away the flexibility by
isolating init and getwave.
The only reason I see for deprecating “Use_Init_Output” was to allow
statistical flow to work independently ...was there any other reason that I
am missing?
If not, then we should have had two IR outputs to EDA tool from Init - one
for statistical and one for further getwave processing (at the same time
allowing IBIS5 compatibity)
Rgds
From: Todd Westerhoff [mailto:twesterh@xxxxxxxxxx]
Sent: Thursday, June 14, 2012 08:13 PM
To: Taranjit Kukal; ibis-macro@xxxxxxxxxxxxx <ibis-macro@xxxxxxxxxxxxx>
Subject: RE: [ibis-macro] Re: AMI-init should pass modified IR to
getwave....
Tananjit,
This therefore violates the basic assumption of AMI … that the channel is
fully described in the impulse response passed to TX_Init.
Attempting to model the RDL after the fact in the algorithmic model will
eliminate any of the reflections / ISI caused by the interaction of the RDL
with the channel.
The RDL needs to be part of the channel model used to generate the impulse
response.
Todd.
Description: cid:EAFF2D52-4B63-4A05-9D24-B96BE375B7E0@eau.wi.charter.com
Todd Westerhoff
VP, Software Products
Signal Integrity Software Inc. • www.sisoft.com <http://www.sisoft.com/>
6 Clock Tower Place • Suite 250 • Maynard, MA 01754
(978) 461-0449 x24 • twesterh@xxxxxxxxxx
“I want to live like that ”
-Sidewalk Prophets
From: Taranjit Kukal [mailto:kukal@xxxxxxxxxxx]
Sent: Thursday, June 14, 2012 10:37 AM
To: 'twesterh@xxxxxxxxxx'; 'ibis-macro@xxxxxxxxxxxxx'
Subject: Re: [ibis-macro] Re: AMI-init should pass modified IR to
getwave....
Hi Todd,
Your description of RDL is correct.
Rx is at the buffer i/p so RDL essentially becomes additional channel.
Rgds
From: Todd Westerhoff [mailto:twesterh@xxxxxxxxxx]
Sent: Thursday, June 14, 2012 07:09 PM
To: 'IBIS-ATM' <ibis-macro@xxxxxxxxxxxxx>
Subject: [ibis-macro] Re: AMI-init should pass modified IR to getwave....
Taranjit,
When you say “On chip RDL”, are you specifically talking about the
interconnect between the die pad and the buffer itself? Where is the
receiver termination physically taking place?
Todd.
Description: cid:EAFF2D52-4B63-4A05-9D24-B96BE375B7E0@eau.wi.charter.com
Todd Westerhoff
VP, Software Products
Signal Integrity Software Inc. • www.sisoft.com <http://www.sisoft.com/>
6 Clock Tower Place • Suite 250 • Maynard, MA 01754
(978) 461-0449 x24 • twesterh@xxxxxxxxxx
“I want to live like that ”
-Sidewalk Prophets
From: ibis-macro-bounce@xxxxxxxxxxxxx
[mailto:ibis-macro-bounce@xxxxxxxxxxxxx] On Behalf Of Taranjit Kukal
Sent: Thursday, June 14, 2012 2:04 AM
To: 'IBIS-ATM'
Subject: [ibis-macro] AMI-init should pass modified IR to getwave....
Hi All,
When I was implementing AMI model, I found a situation where it was
important that Rx ami_init needed to pass modified-IR to getwave function.
Reason was that Chip-RDL-routing was available as Impulse-Responses.
Removal for “Use_Init_Output” to make Statistical-flow independent of
Transient-flow, is going to break the original intent where init and
getwave were supposed to work in conjunction with each other handling linear
and non-linear filtering portions respectively (as shown below)
cid:image001.png@01CD49C5.F040DCA0
I would go back to Arpad’s suggestion (year 2010) for having two
Impulse-responses coming out of ami_init
- One that goes to EDA tool for statistical flow
- One that gets passed to getwave to allow splitting of
modeling-effort across init and getwave and make things easy for linear
filters.
BIRD120 was brought up that deprecates use of “use_init_output” with a view
to keep statistical and time-domain simulations independent. But as I think
more, we need to allow both capabilities. It absolutely does not make sense
to implement simple linear filters within getwave when we can convolute the
filter-IR with channel-IR. We should take all steps to make modeling easy
and ensure enough flexibility.
This way, we cover both the scenarios – those who want to leverage init as
complement to getwave and those who want to keep statistical-flow purely
independent. Since this does not bring any disadvantage, I strongly feel
that we all re-consider outputting two modified-IRs out of init function –
one for statistical-flow and another one to complement getwave filtering.
Rgds
..kukal
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