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

  • From: Mike Steinberger <msteinb@xxxxxxxxxx>
  • To: ibis-macro@xxxxxxxxxxxxx
  • Date: Mon, 12 Dec 2011 13:53:51 -0600

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> [mailto:ibis-macro-bounce@xxxxxxxxxxxxx] <mailto:[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 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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