[ibis-macro] Backchannel and the crosstalk simulation flow
- From: "Muranyi, Arpad" <Arpad_Muranyi@xxxxxxxxxx>
- To: "ibis-macro@xxxxxxxxxxxxx" <ibis-macro@xxxxxxxxxxxxx>
- Date: Tue, 23 Aug 2011 16:29:38 +0000
Hello everyone,
I took an AR last week to start this thread with a few questions
on how the backchannel communication proposal would affect the
existing AMI crosstalk flow.
Summary of the crosstalk flow:
===============================
1) The Tx tap settings of all aggressors and the victim channel
are determined from normal through channel simulations.
2) The AMI_Init functions of the aggressor Tx models will be
used to modify the crosstalk impulse response on the victim
channel.
3) The AMI_Init function of the victim Tx model will be
used to modify the through impulse response on the victim
channel.
4) The Rx model will further process the modified impulse
responses in its AMI_Init and AMI_GetWave functions.
Note that in case the Tx models do not modify the impulse
response in their AMI_Init function, or their AMI_GetWave
function have a glorified version of the algorithm in their
AMI_Init function, the EDA tool will have to use the GetWave
functions of the Tx models on the time domain waveform to
get the correct crosstalk response.
Summary of the Backchannel flow:
================================
The communication between the Tx and Rx GetWave functions
establish the settings of the various coefficients for the
Tx model. Note that this is done in the GetWave functions,
and the AMI_Init function will not be executed after the
backchannel communication finished.
Questions:
==========
1) Backchannel simulations render the AMI Init function
unusable for modifying the impulse response(s) of the channel.
Should we have a rule that in this case the model shall not
return a modified impulse response in the AMI_Init function?
2) The crosstalk flow relies on the AMI_Init function's
modification of the crosstalk (and through) impulse responses.
The outcome of the backchannel communication is not known at
this time. How are we going to incorporate the results of
the training in the crosstalk simulations? Again, should we
have a rule that in this case the model shall not return a
modified impulse response in the AMI_Init function?
3) In case the aggressor's AMI_Init function does not modify
the crosstalk impulse responses, the EDA tool needs to use
the time domain waveforms and use the time domain flow to
figure out the crosstalk effects.
Our spec and BIRDs do not describe the time domain flow for
crosstalk simulations. BIRD 130 (Crosstalk BIRD) was written
to clarify the rule about the Tx model modifying the crosstalk
impulse responses. We did not write anything on how crosstalk
is done in the time domain. Adding the backchannel communication
to the flow, I wonder if we should address these in a more detailed
time domain flow. Is our current time domain flow description
adequate for any EDA vendor and model maker to know how to
implement these features in the tools and models?
There may be more questions, but these might get some discussions
going...
Thanks,
Arpad
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