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

  • From: "Walter Katz" <wkatz@xxxxxxxxxx>
  • To: <Arpad_Muranyi@xxxxxxxxxx>, <ibis-macro@xxxxxxxxxxxxx>
  • Date: Mon, 12 Dec 2011 15:31:24 -0500 (EST)

Arpad,

 

I think it is EXTREMELEY undesirable to prevent Model Specific parameters
from being InOut or Out. There are many cases where IC Vendors want to
report the values of Model Specific parameters to the user. The EDA tool
should not modify the simulation flow based on Out Model Specific
parameters unless they have been formally submitted as BIRDs to the Open
Forum.

 

Walter

 

From: ibis-macro-bounce@xxxxxxxxxxxxx
[mailto:ibis-macro-bounce@xxxxxxxxxxxxx] On Behalf Of Muranyi, Arpad
Sent: Monday, December 12, 2011 3:21 PM
To: ibis-macro@xxxxxxxxxxxxx
Subject: [ibis-macro] Re: How to make tap coefficients Reserved Parameters
with Table

 

Mike,

 

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

intent.

 

Thanks,

 

Arpad

==================================================================

 

 

 

 

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 Table

 

Arpad-

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?

Thanks.
Mike S.

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

Walter,

 

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.

 

Thanks,

 

Arpad

========================================================

 

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

 

Arpad,

 

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 value.

 

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

 

Walter

 

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

 

All,

 

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)

  (Table

    (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)

  (Table

    (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?

 

Thanks,

 

Arpad

================================================================

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