Re[2]: Questions of Polarity and Enable

Text item:

Syed,

Again, these sub-parameters are not required in IBIS. They may be used in the
s2ibis conversion tool, but IBIS doesn't require them, so people don't have to
use them if it doesn't make sense for them.

Arpad
==============================================================================

Hi,

If you are creating an IBIS model based on s2ibis utility, Polarity
and Enable are key in making the conversion work.

For Model_type Input, Polarity=1 sets the input for inverting while
Polarity=0 for non-inverting.

For Model_type I/O or 3-state, both Polarity and Enable fields are
expected. Enable specifies the pin number that enables the associated
output.

Regards,
Syed
National Semiconductor Corp.

>
>
> On Thu, 5 Dec 96 16:59:01 PST Zheng Shi of Symmetry wrote:
>
> >Hi, Ibis folks:
> >
> >Can anyone tell me what the sub-param Polarity and Enable of
> >keyword [Model] really means? Is Polarity used only on diff
> >pins? Is Enable used only on tri-state pins? How can I decide
> >the Polarity and Enable of an input or output pin?
> >
> >I can't find such detail information from IBIS2.1 Specification,
> >can anyone give me some advices, or tell me where i can find
> >the answer?
> >
> >Thanks a lot,
> >
> >-Zheng Shi
> > zheng@symmetry.com
> > Los Altos, CA.
>
> I belive the original intent was to support SSI logic components
> (74OO series TTL and the like) by allowing the user to include
> information on the outputs' logic operation. For example, the model provider
> could specify if the the path from input to output was inverting or
> non-inverting or if the enable on a tri-state output pin was high or
> low. However, for a lot of components (microprocessors, PALS/FPGAS, RAMS,
> etc.) these parameters don't seem to make much sense (to me, anyway). Unless
> you were modeling an SSI component where this made since, I would
> just default them to positive polarity and Active_high.
>
> Ibis old-timmers, any other comments?
>
> Best Regards,
> Stephen Peters
> Intel Corp.
>
>

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Subject: Re: Questions of Polarity and Enable
To: ibis@vhdl.org, ibis-users@vhdl.org, sjpeters@ichips.intel.com
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From: huq@rockie.nsc.com (Syed Huq)
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