[ibis-macro] Re: AMI-init should pass modified IR to getwave....
- From: James Zhou <james.zhou@xxxxxxxxxx>
- To: "kukal@xxxxxxxxxxx" <kukal@xxxxxxxxxxx>, "'twesterh@xxxxxxxxxx'" <twesterh@xxxxxxxxxx>, "'ibis-macro@xxxxxxxxxxxxx'" <ibis-macro@xxxxxxxxxxxxx>
- Date: Thu, 14 Jun 2012 10:48:51 -0700
Taranjit,
One of the main reasons for BIRD120 to "take away the flexibility by isolating
init and getwave" is because passing the IR to Tx_Getwave does not work for
non-linear drivers. This practice had been deprecated in BIRD120.
The differences between the two reference flows (IBIS 5.0 vs. BIRD120) have
been analyzed in the IBIS Quality presentations dated 17-AUG-2011 and
06-SEP-2011, archived at http://www.eda.org/ibis/quality_wip/archive-date.html
The diagram in your original email does not comply with either IBIS 5.0 or
IBIS120. "IR" should not be convolved with TX_Getwave output.
In order to achieve what you need to do, the chip-RDL-routing IR should be
incorporated into the analog channel IR (aka hAC(t)) and, the rest of the
reference flow as specified in BIRDF120 should work fine without problem.
The existing specification (BIRD120 to be adopted by IBIS5.1) has already
achieved what you asked for in the last two paragraphs of your original email,
which had been explained in detail in above presentations.
James Zhou
From: ibis-macro-bounce@xxxxxxxxxxxxx [mailto:ibis-macro-bounce@xxxxxxxxxxxxx]
On Behalf Of Taranjit Kukal
Sent: Thursday, June 14, 2012 8:56 AM
To: 'twesterh@xxxxxxxxxx'; 'ibis-macro@xxxxxxxxxxxxx'
Subject: [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.
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<mailto: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]<mailto:[mailto:twesterh@xxxxxxxxxx]>
Sent: Thursday, June 14, 2012 07:09 PM
To: 'IBIS-ATM' <ibis-macro@xxxxxxxxxxxxx<mailto: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.
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<mailto:twesterh@xxxxxxxxxx>
“I want to live like that ”
-Sidewalk Prophets
From: ibis-macro-bounce@xxxxxxxxxxxxx<mailto:ibis-macro-bounce@xxxxxxxxxxxxx>
[mailto:ibis-macro-bounce@xxxxxxxxxxxxx]<mailto:[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:image002.png@01CD4A17.64816FC0]
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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