[ibis-macro] Re: How to make tap coefficients Reserved Parameters with Table

  • From: "Muranyi, Arpad" <Arpad_Muranyi@xxxxxxxxxx>
  • To: "ibis-macro@xxxxxxxxxxxxx" <ibis-macro@xxxxxxxxxxxxx>
  • Date: Mon, 12 Dec 2011 20:21:05 +0000


These emails might have been flying around too fast, but I
think I have stated it clearly what problem I am trying to
solve.  I will attempt to summarize it again:

We have an unfinished discussion topic on Model_Specific
parameters and InOut/Out.  This was tabled, but it will
soon flare up again (if it hasn't yet with this email
thread).  This topic deals with the issue whether InOut
and Out should ever be allowed in the spec for Model_Specific
parameters, because Model_Specific parameters can't be
adequately described by the spec, and consequently the EDA
tool would not have enough information to know how to deal
with them.  One of the main reasons this notion is being
questioned is the tap parameters, because if the model has
optimization, than it would be desirable to return the
optimized values to the tool so it can display it to the
user.  Up to now we (I) thought that tap parameters can only
be described as Model_Specific parameters, and concluded that
for that reason we must not eliminate Model_Specific
parameters of InOut and Out from the spec.

The idea of making the tap parameters Reserved parameters
was sparked in my mind by the BIRD 123 thread, in which the
question of making them Out or not was brought up.  It occurred
to me that there might be a way to make the tap parameters
Reserved parameters too with the Table syntax.

I do not have any examples for the "added benefit" on what
else the EDA tool could do with them if they were Reserved
parameters, but that is not the main point of this discussion.
The main point is to eliminate the reason for needing InOut
and Out Model_Specific parameters.

Let me know if this doesn't answer your question about my



From: ibis-macro-bounce@xxxxxxxxxxxxx [mailto:ibis-macro-bounce@xxxxxxxxxxxxx] 
On Behalf Of Mike Steinberger
Sent: Monday, December 12, 2011 1:54 PM
To: ibis-macro@xxxxxxxxxxxxx
Subject: [ibis-macro] Re: How to make tap coefficients Reserved Parameters with 


It's not at all clear what problem you're trying to solve.

If you want models to be able to report their tap values to the EDA tool so 
that they can be displayed to the user then, as Walter says, we've already had 
that since IBIS 5.0. For this purpose, what we have in IBIS 5.0 is actually 
better than what you propose because the model can choose to report its state 
using exactly the parameter definitions which most directly apply to the model.

The point is that what Reserved parameters are really useful for is 
communicating directly with the EDA tool and not directly with the user. In 
that context, what would you have the EDA tool do other than report the tap 
values to the user?

Mike S.

On 12/12/2011 01:43 PM, Muranyi, Arpad wrote:

I wasn't talking about added functionality.  The reason
I got into this brain storming is to find a way to make
tap parameters Reserved parameters.  This is motivated
by the discussion of whether InOut and Out should be
allowed with Model_Specific parameters.  Your reason for
wanting that was the tap coefficient example.  Your
argument is that these can be only Model_Specific, and
these need to have the Out capability so that the model
can return its optimized tap coefficients to the EDA tool.
The idea I am proposing is an attempt to make tap parameters
Reserved and thereby being able to make them Out and InOut
without sacrificing the integrity of the specification.

If I understand it correctly, currently we are making
the tap parameters Model_Specific because the number of
taps and their names might be specific to each model which
is hard to make Reserved.

Regarding the "removed functionality", I do not intend to
do that.  This is in the brain storming stage at this
point.  However, the second example indicates that there
might be ways to come up with syntax that includes Range,
Increment, List, and the like.  I don't see a limitation
there, we would just have to define each of these
representations in the spec.



From: Walter Katz [mailto:wkatz@xxxxxxxxxx]
Sent: Monday, December 12, 2011 1:32 PM
To: Muranyi, Arpad; ibis-macro@xxxxxxxxxxxxx<mailto:ibis-macro@xxxxxxxxxxxxx>
Subject: RE: [ibis-macro] How to make tap coefficients Reserved Parameters with 


What you are proposing does not give any additional functionality to what is in 
BIRD 5.0, and in fact removes functionality.

The existing structure allows List, Increment, ... for each Tap. This is 
important because taps does have constrained values. Also taps be InOut or Out. 
Although Table now support "Out", they return the full table, not just the tap 

What in your proposal adds functionality to what already is in IBIS 5.0?


From: ibis-macro-bounce@xxxxxxxxxxxxx<mailto:ibis-macro-bounce@xxxxxxxxxxxxx> 
 On Behalf Of Muranyi, Arpad
Sent: Monday, December 12, 2011 2:24 PM
To: ibis-macro@xxxxxxxxxxxxx<mailto:ibis-macro@xxxxxxxxxxxxx>
Subject: [ibis-macro] How to make tap coefficients Reserved Parameters with 


I just couldn't leave this idea alone, and looked at
BIRD 132 to see how Tables could be used for taps.
Here is an example that I can imagine:

(DFE_taps (Usage InOut) (Type String Float)
    (Labels "Tap name" "Tap value")
    ("tp-1"  -0.1)
    ("tp0"    0.8)
    ("tp1"    0.1)
  (Description "Initial DFE tap coefficients.")

I don't see why this couldn't be under the Reserved parameters
section.  Note that it doesn't have to be a required parameter
because not all models may have a DFE.  The specification can
provide a detailed description on when/how/why this parameter
is used by the EDA tool and model, etc...

A more elaborate version of the above example is an equivalent of
the example on pg. 150 of the v5.0 spec (including Range and Default):

(DFE_taps (Usage InOut) (Type String Float Float Float Float)
    (Labels "Tap name" "Typ value" "Min value" "Max value" "Default value")
    ("-2"   0.1  -0.1  0.2  0.1)
    ("-1"   0.2  -0.4  0.4  0.2)
    ("0"    1    -1    2    1)
    ("1"    0.2  -0.4  0.4  0.2)
    ("2"    0.1  -0.1  0.2  0.1)
  (Description "DFE tap coefficients.")

Comments?  Questions?



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