[ibis-macro] Re: Unanswered question from last week.
- From: Walter Katz <wkatz@xxxxxxxxxx>
- To: "David Banas" <DBanas@xxxxxxxxxx>, <ibis-macro@xxxxxxxxxxxxx>
- Date: Wed, 16 Apr 2014 07:33:54 -0400 (EDT)
David,
Suppose a user sets up a simulation with Tx tap coefficients -.15,.85,0.
for taps -1, 0 and 1 respectively.
And then suppose the Tx AMI_Init function changed the tap settings to
-.2,.75,-.05. There is no requirement in the spec that the Tap parameter
be an InOut, so if it was an In, how does the user know that the tap
coefficients have changed? And if they have changed, what have they
changed to? How does the user know how to program his BIOS to optimize the
operation of the channel?
Even if the Tap was InOut, and it reported to the user what the change was
the user is going to get a performance result using -.2,.75,-.05. which
will give him a more open eye at the input to the Rx but a worse eye at
the output of the Rx.
Your response, very importantly, included the following "and if the user
has opted to NOT use the Tx model 'co-opt' mode, but rather to use some
'auto' feature of the Tx model". So you are saying that the Tx model NEEDS
a 'auto feature that can be turned on and off. This is exactly what I said
when I said for Redriver Tx and for Tx involved in co-optimization. I
suggested a reserved parameter to turn the Tx self-optimization on and
off. So we either force the user to read the Tx Model users guide to
figure this out, or use a reserved parameter. In any case I believe the
user should control this, and not leave it solely up to the Tx model to
make this decision as you suggested in your question.
Walter
From: David Banas [mailto:DBanas@xxxxxxxxxx]
Sent: Tuesday, April 15, 2014 5:17 PM
To: Walter Katz; ibis-macro@xxxxxxxxxxxxx
Subject: RE: [ibis-macro] Unanswered question from last week.
I think my original question is more true to my intended inquiry, than
either alternative you propose.
And, understand that the case I'm envisioning is one in which the user
doesn't want EDA tool driven co-optimization to occur. (Otherwise, he'd do
that.)
In such an instance, and if the user has opted to NOT use the Tx model
'co-opt' mode, but rather to use some 'auto' feature of the Tx model, in
which that model chooses the optimum FIR coefficients based solely upon
the channel impulse response and not expecting to take part in any Tx/Rx
co-optimization, why must the Tx AMI_Init() function alert the EDA tool
that it has done so?
(Mike M., that is what you were suggesting; right?)
Thanks,
-db
From: Walter Katz [mailto:wkatz@xxxxxxxxxx]
Sent: Tuesday, April 15, 2014 1:29 PM
To: David Banas; ibis-macro@xxxxxxxxxxxxx
Subject: RE: [ibis-macro] Unanswered question from last week.
David,
Your statement is not quite correct. I think the statement should be:
Why must the Tx .ami file tell the EDA tool, if it assisted the user in
choosing "optimum" tap weights?
or
Why must the Tx .ami file tell allow the EDA tool to tell the Tx
AMI_Init() to assist the user in choosing "optimum" tap weights?
The reason for letting the EDA tool know what the Tx AMI_Init() function
is doing (or controlling what the Tx AMI_Init() function is doing is
important in co-optimization, particularly in the statistical flow. The Rx
AMI_Init needs to know the Tx equalization used to generate the input to
the Rx AMI_Init, and when the Rx AMI_Init returns an optimized Tx tap
coefficients, the Tx AMI_Init function needs to be called with these
coefficients, and the Tx AMI_Init must use the equalization for these tap
coefficients.
Does this answer your question?
Walter
From: ibis-macro-bounce@xxxxxxxxxxxxx
[mailto:ibis-macro-bounce@xxxxxxxxxxxxx] On Behalf Of David Banas
Sent: Tuesday, April 15, 2014 2:30 PM
To: ibis-macro@xxxxxxxxxxxxx
Subject: [ibis-macro] Unanswered question from last week.
Hi all,
I asked a question, at the end of Walter's presentation last week, which I
don't think was ever answered. So, I'd like to ask it, again:
Why must the Tx AMI_Init() function tell the EDA tool, if it assisted the
user in choosing "optimum" tap weights?
(How, for instance, is this use case different than the user relying on,
say, MATLAB to help him find optimum tap weights and setting those
MATLAB-prescribed values in the AMI model, by hand?)
Thanks,
-db
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