[ibis-macro] Re: input to Tx analog model
- From: <fangyi_rao@xxxxxxxxxxx>
- To: <Arpad_Muranyi@xxxxxxxxxx>, <ibis-macro@xxxxxxxxxxxxx>
- Date: Thu, 20 Jan 2011 15:33:04 -0700
Arpad;
Yes, we are asking the same questions. While yours are more focusing on AMI
simulation, mine are focusing on general SPICE transient simulation. A subtitle
difference is that in AMI it's the EDA tool that internally create the input to
Tx analog models but in transient user has to create the input explicitly on
the schematic. So these questions are more prominent in transient simulations.
Regards,
Fangyi
From: ibis-macro-bounce@xxxxxxxxxxxxx [mailto:ibis-macro-bounce@xxxxxxxxxxxxx]
On Behalf Of Muranyi, Arpad
Sent: Thursday, January 20, 2011 2:16 PM
To: ibis-macro@xxxxxxxxxxxxx
Subject: [ibis-macro] Re: input to Tx analog model
Fangyi,
You are basically asking the same question to which I was
trying to find the answer in the last few ATM meetings and
email discussions on the topic of the AMI analog models.
The difference you describe is exactly why I am now asking
the questions "what is ***the*** analog model" or AMI? Is
the stimulus PWL source included or not? Do we need two
different types of models? Do we need to describe the
different usages and/or flows... I still do not see the end
of the tunnel in this discussion.
I thought when Walter posted his HSPICE netlist
http://www.vhdl.org/pub/ibis/macromodel_wip/archive/20101214/walterkatz/BIRD%20122%20Sample%20SPICE%20Deck/generic_tstonefile_spice.pdf
that we had the answer. But when Walter brought up the
possibility of using the output of Tx GetWave as the input
to the Tx analog model, I lost that feeling. I am still
looking for answers and suggestions on how to write the
specification in an unambiguous way to describe the analog
models.
I am open to any suggestions...
Thanks,
Arpad
============================================================
From: ibis-macro-bounce@xxxxxxxxxxxxx [mailto:ibis-macro-bounce@xxxxxxxxxxxxx]
On Behalf Of fangyi_rao@xxxxxxxxxxx
Sent: Wednesday, January 19, 2011 9:11 PM
To: ibis-macro@xxxxxxxxxxxxx
Subject: [ibis-macro] input to Tx analog model
Hi, Experts,
In light of IBIS analog model enhancement discussed at recent ATM meetings, I
want to raise a question: in SPICE level transient simulations (w/o AMI), what
is the input signal to the Tx analog model?
In IBIS 5.0 the answer is simple. The input is digital signal whose threshold
crossing events trigger rise and fall edges being formed and transmitted. The
swing and waveform of the edges are part of the analog model. They are
independent of the input signal and user doesn't need to know about them.
If we are to make Tx analog model able to accept AMI_GetWave output waveform as
input, we need to abandon this notion of event trigger and make the input
signal a continuous analog waveform (e.g. PWL). The output waveform of Tx
analog model will be directly shaped by the input waveform. As a result, to run
a SPICE level transient simulation (w/o AMI) user has to look up the swing and
slope parameters (Voh, Vol, trise, etc) from model files in order to create the
input signal with proper amplitude and shape.
Is this an acceptable use model for transient? If user replace his old model
with a new one, then the result is most likely wrong because his old digital
input signal doesn't have the correct amplitude and slope.
Regards,
Fangyi
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