[ibis-macro] Re: Samples_per_bit question

  • From: ckumar <ckumar@xxxxxxxxxxx>
  • To: <Arpad_Muranyi@xxxxxxxxxx>
  • Date: Wed, 20 Jul 2011 15:32:29 -0700

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That is a bad practice which should not be encouraged. 
I emphasize again the models have to treat the incoming wave form as
continuous waveform like a real device.
The samples per bit is only an issue internal to  the model and such
nuances should not be elevated to a reserved parameter level

On Wed, 20 Jul 2011 22:23:50 +0000, "Muranyi, Arpad"
<Arpad_Muranyi@xxxxxxxxxx> wrote:
> Kumar,
> 
> While this may be poor practice, how would you enforce any
> better practice without such a parameter in the spec?  Please
> remember, that the goal of using such a parameter is not to
> encourage the model maker to write models which work with a
> single option for samples per bit.  This parameter could define
> a discrete or continuous range of such values.  The point in
> having such a required parameter is to force the model makers
> to think about this issue.   I feel that the reason we currently
> see models which work only at certain samples per bit values
> is because (inexperienced) model makers don't even think about
> the possibility and consequences of different samples per bit
> values...
> 
> Arpad
> ==================================================================
> 
> 
> -----Original Message-----
> From: ibis-macro-bounce@xxxxxxxxxxxxx
> [mailto:ibis-macro-bounce@xxxxxxxxxxxxx] On Behalf Of ckumar
> Sent: Wednesday, July 20, 2011 5:08 PM
> To: Muranyi, Arpad
> Cc: ibis-macro@xxxxxxxxxxxxx
> Subject: [ibis-macro] Re: Samples_per_bit question
> 
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> 
> making it required reserved parametr is perpetuating an extremely poor
> practice
> 
> On Wed, 20 Jul 2011 22:04:59 +0000, "Muranyi, Arpad"
> <Arpad_Muranyi@xxxxxxxxxx> wrote:
>> Kumar,
>> 
>> The EDA tool can resample the waveform(s) between
>> the Tx and Rx calls according to their own needs...
>> 
>> Arpad
>> ====================================================
>> 
>> -----Original Message-----
>> From: ckumar [mailto:ckumar@xxxxxxxxxxx] 
>> Sent: Wednesday, July 20, 2011 5:00 PM
>> To: Muranyi, Arpad
>> Cc: ibis-macro@xxxxxxxxxxxxx
>> Subject: Re: [ibis-macro] Re: Samples_per_bit question
>> 
>> I do not agree with that. 
>> What happens if the tx and rx requires different samples per bit?
Things
>> can get convoluted very fast.
>> 
>> That is why the emphasis should be on that the models are always seeing
>> continuous signals. Any way that is what devices do in real life too.
> They
>> sample a continuous signal coming into them. Software should be no
>> different.
>> 
>> On Wed, 20 Jul 2011 21:47:23 +0000, "Muranyi, Arpad"
>> <Arpad_Muranyi@xxxxxxxxxx> wrote:
>>> Mike, Scott, Kumar,
>>> 
>>> First, the models I ran into recently were brand new models,
>>> probably not even released yet.  I don't know the reason, but
>>> it appears that the problem might be learning curve related
>>> on the author's part.
>>> 
>>> This is why I tend to not agree with requiring the models to
>>> do the re-sampling for themselves.  This is extra burden on
>>> the model makers which we should try to avoid.  EDA vendors
>>> are probably better at writing such algorithms, and if the
>>> EDA vendor knows what sampling rate the model works with
>>> (using the proposed required and reserved parameter for that),
>>> they can do the re-sampling for the model if necessary before
>>> executing it.
>>> 
>>> I would prefer to put this Sample_per_bit parameter in the
>>> AMI spec, and make it required, reserved.
>>> 
>>> 
>>> Ambrish,
>>> 
>>> I agree that "to require a certain samples_per_bit for the model to
> work
>>> is not good"
>>> but it does happen unfortunately.  But I am not sure what you mean
>>> by "We can deal with this at a tool level and not put anything in the
>>> spec".  How would
>>> the tool know how to deal with a certain model if it doesn't know
>>> what sample rate(s) the model works with?  I think the only way
>>> a tool can deal with this if every model would be required to
>>> tell the tool with a reserved parameter what its sampling rate
>>> needs/capabilities are.
>>> 
>>> Thanks,
>>> 
>>> Arpad
>>> =====================================================================
>>> 
>>> 
>>> From: ibis-macro-bounce@xxxxxxxxxxxxx
>>> [mailto:ibis-macro-bounce@xxxxxxxxxxxxx] On Behalf Of Mike Steinberger
>>> Sent: Wednesday, July 20, 2011 4:17 PM
>>> To: ibis-macro@xxxxxxxxxxxxx
>>> Subject: [ibis-macro] Re: Samples_per_bit question
>>> 
>>> Scott-
>>> 
>>> Moving forward, we could conceivably take the approach you suggest.
> That
>>> approach still doesn't address the models that are already out there,
>>> however. I, for one, don't want to be in the position of telling users
>> they
>>> can no longer run models that they've been running for years.
> (Actually,
>> I
>>> know for a fact that I personally won't be in that position, so it's
>> really
>>> a choice for others to make.)
>>> 
>>> Mike S.
>>> 
>>> On 07/20/2011 03:53 PM, Scott McMorrow wrote:
>>> Ambrish
>>> 
>>> Why not go the other direction, which would be to explicitly require
>> that
>>> the model perform sample rate conversion to any sample rate.
>>> 
>>> Scott
>>> 
>>> 
>>> 
>>> 
>>> Scott McMorrow
>>> 
>>> Teraspeed Consulting Group LLC
>>> 
>>> 121 North River Drive
>>> 
>>> Narragansett, RI 02882
>>> 
>>> (401) 284-1827 Business
>>> 
>>> (401) 284-1840 Fax
>>> 
>>> 
>>> 
>>> http://www.teraspeed.com
>>> 
>>> 
>>> 
>>> Teraspeed(r) is the registered service mark of
>>> 
>>> Teraspeed Consulting Group LLC
>>> 
>>> On 7/20/2011 4:49 PM, Ambrish Varma wrote:
>>> I think we all agree that to require a certain samples_per_bit for the
>>> model to work is not good. We can deal with this at a tool level and
> not
>>> put anything in the spec as this will most definitely give it more
>>> prominence. In other words, model makers will feel compelled to 'do
>>> something' with this parameter.
>>> My 2 cents.
>>> 
>>> -Ambrish.
>>> 
>>> 
>>> 
>>> 
>>> [cid:image002.gif@01CC46FB.CCC6FBB0]
>>> 
>>> 
>>> 
>>> Ambrish Varma   |  Member of Consulting Staff
>>> 
>>> P: 978.262.6431   www.cadence.com<http://www.cadence.com>
>>> 
>>> 
>>> 
>>> 
>>> 
>>> 
>>> 
>>> 
>>> 
>>> 
>>> ________________________________
>>> From:
>>>
ibis-macro-bounce@xxxxxxxxxxxxx<mailto:ibis-macro-bounce@xxxxxxxxxxxxx>
>>> [mailto:ibis-macro-bounce@xxxxxxxxxxxxx] On Behalf Of Dmitriev-Zdorov,
>>> Vladimir
>>> Sent: Wednesday, July 20, 2011 4:25 PM
>>> To: msteinb@xxxxxxxxxx<mailto:msteinb@xxxxxxxxxx>;
>>> ibis-macro@xxxxxxxxxxxxx<mailto:ibis-macro@xxxxxxxxxxxxx>
>>> Subject: [ibis-macro] Re: Samples_per_bit question
>>> 
>>> 
>>> Agree,
>>> 
>>> 
>>> 
>>> We also encountered with such models. The problem is when something
> does
>>> not work it is difficult to guess what's the problem and even after
> that
>> it
>>> takes several tries to find an appropriate parameter.
>>> 
>>> 
>>> 
>>> Vladimir
>>> 
>>> 
>>> From:
>>>
ibis-macro-bounce@xxxxxxxxxxxxx<mailto:ibis-macro-bounce@xxxxxxxxxxxxx>
>>> [mailto:ibis-macro-bounce@xxxxxxxxxxxxx] On Behalf Of Mike Steinberger
>>> Sent: Wednesday, July 20, 2011 2:18 PM
>>> To: ibis-macro@xxxxxxxxxxxxx<mailto:ibis-macro@xxxxxxxxxxxxx>
>>> Subject: [ibis-macro] Re: Samples_per_bit question
>>> 
>>> Kumar-
>>> 
>>> We agree with you in principle, and on the two occasions (years ago
> now)
>>> when we encountered a model that required a specific number of samples
>> per
>>> bit, we did ask the model developers to make their models more
general.
>>> Unfortunately, neither the IBIS spec nor any customer required them to
>>> support an arbitrary number of samples per bit, so the model
developers
>> did
>>> not accept our suggestion.
>>> 
>>> These models have now been in widespread use for several years. Given
>>> that, how should we handle the problem? To date, the solution we've
>>> proposed is the Samples_per_bit reserved parameter.
>>> 
>>> Thanks.
>>> Mike S.
>>> 
>>> On 07/20/2011 03:07 PM, ckumar wrote:
>>> 
>>> the ami model should treat the waveforms as continuous. They should
>>> 
>>> resample it inside the model for their requirements.
>>> 
>>> Requiring specific sample size is an unnecessary constraint.
>>> 
>>> On Wed, 20 Jul 2011 19:44:03 +0000, "Muranyi, Arpad"
>>> 
>>> <Arpad_Muranyi@xxxxxxxxxx><mailto:Arpad_Muranyi@xxxxxxxxxx> wrote:
>>> 
>>> Hello everyone,
>>> 
>>> 
>>> 
>>> I recall that we asked Walter to remove the proposed Samples_per_bit
>>> 
>>> Reserved AMI parameter from BIRD 121, which he did in BIRD 121.1.
>>> 
>>> What I don't remember is whether we made this request because we
>>> 
>>> decided that we didn't want/need this reserved parameter in the AMI
>>> 
>>> specification at all, or whether we just didn't want to propose this
>>> 
>>> in BIRD 121, since it seemed unrelated to the rest of the BIRD 121
>>> 
>>> content.  Could someone please refresh my memory on that?
>>> 
>>> 
>>> 
>>> The reason I am asking is because just recently I ran across a couple
>>> 
>>> of AMI models which only work at certain samples per bit settings
>>> 
>>> but there was no documentation that I am aware of that came with the
>>> 
>>> model that stated that.
>>> 
>>> 
>>> 
>>> I am not sure if this was done intentionally by the model's authors,
>>> 
>>> but it seems that a required reserved parameter would at least serve
>>> 
>>> as a reminder to the model makers to document the value at which
>>> 
>>> their model works, if not remind them to write models that work at
>>> 
>>> any reasonable samples per bit values.
>>> 
>>> 
>>> 
>>> Based on this experience I tend to feel that a required, and reserved
>>> 
>>> parameter for Samples_per_bit would be very useful in the AMI spec...
>>> 
>>> 
>>> 
>>> Comments, suggestions are welcome.
>>> 
>>> 
>>> 
>>> Thanks,
>>> 
>>> 
>>> 
>>> Arpad
>>> 
>>> ======================================================================
>>> 
>>> ---------------------------------------------------------------------
>>> 
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