[ibis-macro] Re: Samples per bit for AMI

  • From: ckumar <ckumar@xxxxxxxxxxx>
  • To: <wkatz@xxxxxxxxxx>
  • Date: Thu, 29 Sep 2011 07:14:38 -0700

That is like going backwards. The samples per bit is a model's
responsibility and internal to the model (for example adc and its own
internal simple or complex 'torque converter' ). I do not see a reason to
encourage and perpetuate a wrong practice

should not be suppored by a future reserved parameter. 
On Thu, 29 Sep 2011 10:08:20 -0400 (EDT), "Walter Katz" <wkatz@xxxxxxxxxx>
wrote:
> Greg,
> 
>  
> 
> If an AMI model does have a Sample_Per_Bit requirement, then the EDA
tool
> must do one of the following:
> 
> 1.       Choose a samples per bit that satisfies all of the Tx and Rx
> samples per bit requirements - not always possible when different models
> have different samples per bit requirements.
> 
> 2.       Choose a samples per bit for a simulation, and then run the
> impulse response and waveforms through a Torque Converter (Gearbox) that
> converts these waveforms to the model's required Samples_Per_Bit before
> calling the model, and then run the output of the model back to the
Torque
> Converter backwards.
> 
>  
> 
> In the ideal world, if the internals of the model do have a
> Samples_Per_Bit limitation, the model should be doing the Torque
> Conversions described above.
> 
>  
> 
> According to IBIS 5.0 (and the proposed 5.1), a model which does have a
> Samples Per Bit limitation is non-compliant. If we add a reserved
> parameter Samples_Per_Bit in IBIS 5.2, then these models can be made
> compliant to 5.2 if they specify Samples_Per_Bit in the .ami file.
> 
>  
> 
> Ken Willis made in a separate e-mail branch:
> 
>  
> 
> Good discussion. I agree it is good practice to document the model
usage.
> If the issue is really one of documentation, then I don't know if it is
> something we have to put into the standard. Most of the IBIS-AMI model
> kits have some readme or pdf documentation with them. This is not really
> different than regular Spice or IBIS models that have been distributed
for
> many years. With AMI, you can even put comments into the .ami files
> themselves. So there are ways to properly document the models, without
> adding more keywords to the spec.
> 
>  
> 
> Unfortunately, model makers often do not document the Samples Per Bit
> limitation, and in some cases do not realize they have a Samples Per Bit
> limitation because they only test them at one Samples Per Bit. Also, it
is
> difficult for software to programmatically read these .pdf files and
> extract Samples Per Bit limitations.
> 
>  
> 
> We certainly can add a compliance test to IBIS-AMI that would use the
AMI
> test benches to verify that a model works at any number of Samples Per
> Bit.
> 
>  
> 
> Walter
> 
>  
> 
>  
> 
> From: ibis-macro-bounce@xxxxxxxxxxxxx
> [mailto:ibis-macro-bounce@xxxxxxxxxxxxx] On Behalf Of Gregory R Edlund
> Sent: Thursday, September 29, 2011 9:32 AM
> To: Arpad_Muranyi@xxxxxxxxxx
> Cc: IBIS-ATM; ibis-macro-bounce@xxxxxxxxxxxxx
> Subject: [ibis-macro] Re: Samples per bit for AMI
> 
>  
> 
> Arpad,
> 
> Do you envision the new samples per bit parameter being used by the EDA
> tool?  Or is it for documentation purposes?
> 
> There is another way to handle this scenario:  we could integrate
samples
> per bit into the quality check list, i.e. the model maker uses the
quality
> check list as a means of communication with the user.
> 
> Greg Edlund
> Senior Engineer
> Signal Integrity and System Timing
> IBM Systems & Technology Group
> 3605 Hwy. 52 N  Bldg 050-3
> Rochester, MN 55901
> 
> 
> 
> Inactive hide details for "Muranyi, Arpad" ---09/28/2011 06:44:32
> PM---Hello everyone, I ran across yet another model today whi"Muranyi,
> Arpad" ---09/28/2011 06:44:32 PM---Hello everyone, I ran across yet
> another model today which was misbehaving
> 
> From: "Muranyi, Arpad" <Arpad_Muranyi@xxxxxxxxxx>
> To: IBIS-ATM <ibis-macro@xxxxxxxxxxxxx>
> Date: 09/28/2011 06:44 PM
> Subject: [ibis-macro] Samples per bit for AMI
> Sent by: ibis-macro-bounce@xxxxxxxxxxxxx
> 
>   _____  
> 
> 
> 
> 
> Hello everyone,
> 
> I ran across yet another model today which was misbehaving
> in our tool because it turned out that it would only work
> with 64 samples per bit and the user unaware of this used a
> different value.
> 
> When I wrote about this topic some time ago, I was wrestling
> with another AMI model that would only work with 32 samples
> per bit.  Neither of these models came with any documentation
> on what samples per bit settings they will work with.  The
> problem is that when such models are misbehaving, all kinds
> of "fun stuff" is starting to happen, anywhere from crashes
> to explosions  :-).
> 
> I believe that the most robust solution would be to add a
> reserved parameter for samples per bit to the IBIS-AMI
> specification so that the model makers would be forced to
> document in the .ami parameter file sampling rate(s) the
> model will work with.  Making blanket statements in the spec
> is not going to guarantee  that the model maker will actually
> do anything about it, they may not even read that part of
> the specification at all...
> 
> Please look over the attached BIRD draft in which I attempt
> to solve this problem by adding a reserved parameter to the
> specification.
> 
> Questions, comments are welcome.
> 
> Thanks,
> 
> Arpad
> ==============================================================
> 
> 
> 
> [attachment "SamplingRateBIRD_01.pdf" deleted by Gregory R
> Edlund/Rochester/IBM]
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