RE: [IBIS-Users] [Submodel] and [Add Submodel] keywords

Timmy,
 
1)  The submodel keywords were not "invented" for the purpose
of reducing file size.  Their purpose was to model specific
behaviors of specific circuit types.  The dynamic clamp, for 
example, is a special circuit in the buffer which moves the
origin of the I-V curve in to clamp stronger when there is a
transition in the waveform to "catch" overshooting and clamp
them better.  The bus hold is a similar special circuitry to
implement some sort of a dynamic termination while reducing
DC current consumption during long series of ones or zeroes
on the line.
 
While there may be other legitimate uses, be careful about
all of the details to "get it right".  Also beware that not
all EDA vendors may support all variants of these keywords...
 
2)  I am not sure how to answer this question at this point,
and I don't have the time to research it, so I will let someone
else answer it...
 
Arpad
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________________________________

From: owner-ibis-users@server.eda.org [mailto:owner-ibis-users@server.eda.org] On Behalf Of Ibis Model
Sent: Wednesday, October 03, 2007 2:19 AM
To: Server EDA
Subject: [IBIS-Users] [Submodel] and [Add Submodel] keywords


Hi forum posters,
 
I tried to find the previous threads on [Submodel] and [Add Submodel] keywords to no avail, so here I'm posting yet another question. I understand that I have been posting questions a lot lately, so bear with me if anyone is getting bored with me spamming the forum. I have another two questions: 
 
1. I find the [Submodel] and [Add Submodel] keywords very useful in shrinking the IBIS models file size. Assuming an IBIS models file containing 100 models and all sharing the same [Ground Clamp] and [Power Clamp] data. In this case, I can reduce the file size by using the keyword [Add Submodel] to refer to a [Submodel] that contains these [GND Clamp] and [POWER Clamp] data, thus avoiding to repeat the [GND Clamp] and [Power Clamp] data for each model for 100 times. 
 
While I manage to reduce the file size of the IBIS models by ~20%, is this technically the correct usage of the keywords? What does it exactly mean by a "Dynamic_clamp Submodel"?
 
2.  I understand from the IBIS spec that the keyword [Test Load] was used to derive the golden waveform. Will there be a problem if  define the [Test Load] keyword with the respective electrical parameters such as Rs_near, Vterm, Rp1_near on my driver without defining the [Test Data] keyword as well as not having a golden waveform for that IBIS model. 
 
This doesn't prompt me any warning when I perform the syntax check but I'm worried that this could be technically wrong as well. Please advice.  
 
Regards,
Timmy



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