[ibis-macro] Re: AMI Analog Modeling
- From: "Muranyi, Arpad" <Arpad_Muranyi@xxxxxxxxxx>
- To: IBIS-ATM <ibis-macro@xxxxxxxxxxxxx>
- Date: Wed, 2 Jan 2013 20:37:55 +0000
Walter,
Regarding "AMI simulations assume that there is a zero impedance voltage source
at the Tx end of the analog model and an infinite impedance Probe at the Rx end
of the
analog model.", unfortunately this assumption is not spelled out in
the specification. Considering that "According to the reference flows, to
do a time domain simulation, the waveform that is input to Rx AMI_GetWave is the
waveform generated by Tx AMI_GetWave convolved with the impulse response of the
channel" the implication is that the GetWave flow deals with signal
processing in which there are no voltages and currents or Ohm's
and Kirchhoff's laws, etc..., i.e. there is no circuit simulation,
only signal number crunching. We think of these signals as a voltage
vs. time waveform, but in reality they could be anything, such as the
CO2 content of the atmosphere vs. the number of cars sold.
As long as we don't spell out the assumption you stated, we can
only talk about signal processing in the AMI_GetWave flow which
excludes the alternate way of doing the AMI_GetWave flow as you
described below.
Regarding "This method is not available with the IBIS analog model (either
Legacy IV,
or External Model) because of the interpretation of IBIS models in External
Model that
they have digital inputs", we can't blame the [External Model] for this.
I am preparing a presentation of the next ATM meeting and I will
try to show a few interesting details on this topic.
Thanks,
Arpad
====================================================================
From: ibis-macro-bounce@xxxxxxxxxxxxx [mailto:ibis-macro-bounce@xxxxxxxxxxxxx]
On Behalf Of Walter Katz
Sent: Friday, December 21, 2012 8:38 AM
To: IBIS-ATM
Subject: [ibis-macro] AMI Analog Modeling
All,
AMI modeling assumes there is an analog channel that can be represented by an
impulse response. AMI simulations assume that there is a zero impedance voltage
source at the Tx end of the analog model and a infinite impedance Probe at the
Rx end of the analog model.
The impulse response of the channel can be generated a number of ways. One way
is to do a time domain step response of the channel, the impulse response is
the derivative of the waveform at the Rx. A second way is to cascade into a
single s4p the Tx buffer analog model represented as an s4p, the channel (die
to die) represented as an s4p and the Rx buffer analog model represented as an
s4p. The two impulse responses should be identical (within numerical
precision/accuracy). There can be other methods of generation this impulse
response.
According to the reference flows, to do a time domain simulation, the waveform
that is input to Rx AMI_GetWave is the waveform generated by Tx AMI_GetWave
convolved with the impulse response of the channel. An alternative method of
generating the waveform at the Rx AMI_GetWave is to do a time domain simulation
using the waveform generated by Tx AMI_GetWave (mad differential) as input to
the cascaded s4p defined above, and probing the waveform at the Rx end of the
cascaded s4p. This method is not available with the IBIS analog model (either
Legacy IV, or External Model) because of the interpretation of IBIS models in
External Model that they have digital inputs.
One really needs to understand these statements to understand how AMI analog
modeling is fundamentally different than the existing interpretation that IBIS
models have digital inputs.
Walter
Walter Katz
wkatz@xxxxxxxxxx<mailto:wkatz@xxxxxxxxxx>
Phone 303.449-2308
Mobile 303.335-6156
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