[ibis-macro] Re: A rephrasing of my previous question, re: your GetWave() approach.
- From: David Banas <DBanas@xxxxxxxxxx>
- To: "'msteinb@xxxxxxxxxx'" <msteinb@xxxxxxxxxx>, "'ibis-macro@xxxxxxxxxxxxx'" <ibis-macro@xxxxxxxxxxxxx>
- Date: Thu, 10 Jan 2013 14:25:42 -0800
Hi Mike,
Happy New Year! Thanks for the response. Please, see below.
Thanks,
-db
From: ibis-macro-bounce@xxxxxxxxxxxxx [mailto:ibis-macro-bounce@xxxxxxxxxxxxx]
On Behalf Of Mike Steinberger
Sent: Thursday, January 10, 2013 11:50 AM
To: ibis-macro@xxxxxxxxxxxxx
Subject: [ibis-macro] Re: A rephrasing of my previous question, re: your
GetWave() approach.
Dave-
At the very considerable risk of jumping into the middle of a conversation I
haven't been a part of, I suggest that for a given simulation, the presumed
physical location of the output needs to be the same for Init() and GetWave().
[David Banas] But your colleague, Walter, just made us all aware, last week, of
the error in this assumption, by referring us to Sec. 10 of IBIS v5.1 and
encouraging us to carefully re-read it, which we did. (Before that, I would've
agreed with what you're saying, here.)
1. If the presumed physical location of the output is the input to the Rx Eq,
then however the EDA tool does its business, the net result should be the input
to the Rx Eq. for both statistical analysis and time domain simulation.
[David Banas] I agree, and like the consistency you're suggesting.
This choice is only valid if the Tx model is linear, in which case there are
several options open to the EDA tool developer, all of which are mathematically
equivalent.
[David Banas] Do you mean the entire Tx model must be linear, or just the
analog portion? If I suggested that:
1. In the Init() case, the entire model must be linear, but
2. In the GetWave() case, only the analog portion need be linear,
How would you reply?
2. If the presumed physical location of the output is the input to the analog
channel, then however the EDA tool does its business the net result should be
the input to the analog channel for both statistical analysis and time domain
simulation. This choice is valid for both linear or nonlinear Tx models. <This
is the cue for the usual discussion about interactions between a nonlinear
driver and a linear channel. Could we forgo that conversation just this once?>
The choices open to the EDA tool developer are a bit more limited in this case,
but there are definitely valid options available.
[David Banas] Do any of them support the use of an IBIS [Model] in its legacy
interpretation (i.e. - binary control input)? If so, are you at liberty to
provide such an example to this group?
The EDA tool should be consistent about which of these two options it chooses
for a given simulation.
[David Banas] Whoa! I wouldn't have ever suspected that the EDA tool had the
latitude to choose; could you explain this, please?
Most Tx models will support either choice, in which case the EDA tool is free
to choose.
[David Banas] The choice being dictated by the EDA tool, via what it chooses to
send into GetWave() as input, or am I lost?
There are, however, some models out there, both Tx and Rx, which are only valid
for one or the other of these two options. Therefore, the EDA tool has to make
a choice which is consistent with the models it's running.
[David Banas] Confining the discussion to just the Tx for now, is this simply a
matter of whether or not a particular model supplies a GetWave() function, or
is there more to it than that? That is, can GetWave() be written in a such a
way as to preclude this choice. If so, how?
This is admittedly a very academic approach to your question because I don't
want to go into specifics any more than anyone else does.
[David Banas] I completely understand, and I appreciate your response.
Hope this helps.
Mike Steinberger
On 01/10/2013 01:23 PM, David Banas wrote:
Hi all,
At the end of yesterday's meeting, I asked the EDA vendors in the group if
they'd describe their GetWave() flows, for Tx modeling, to the group.
This request drew quite a bit of reluctance, understandably. I would like to
rephrase my question:
In the case of Tx modeling only, what processing flexibility do you gain by not
being required to accept the channel impulse response as input to the GetWave()
function?
My hope is that the above question is safer to answer and, yet, might still
further our common understanding of the reasons for the different assumptions,
regarding input signal and output location, made for Init() and GetWave(). If
you'll recall, after our recent re-read of Sec. 10 of IBIS v5.1 (and if we
agree to take Sec. 10 as a normative part of the standard, as opposed to just
one example interpretation of it), those assumptions are:
Flow Type
Input Signal
Presumed Physical Location of Output
Init()
Channel Impulse Response
Input to Rx Eq.
GetWave()
Binary Data Stream
Input to analog channel
If I am merely the last person to understand the motivation for the different
assumptions, above, I apologize for my obtuseness and thank you, in advance,
for your indulgence.
Best regards,
David Banas
Sr. Member Technical Staff
Altera<http://www.altera.com/>
+1-408-544-7667 - desk
Did you know Altera offers over 150 free online technical training
courses<http://www.altera.com/servlets/searchcourse?coursetype=Online&WT.mc_id=t9_ot_mi_mi_tx_a_311>?
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