Re: [IBIS-Users] s2ibis2 problem with 3-stateable OD drivers

Subject: Re: [IBIS-Users] s2ibis2 problem with 3-stateable OD drivers
From: Fred Balistreri (fred@apsimtech.com)
Date: Wed Nov 27 2002 - 08:18:29 PST

Hello Henrik, the correct pin type to use is I/O_open_sink or drain
which ever you prefer. If you use Open_sink or Open_drain then it
is assumed that the part is a driver only. The I/O is what tells the
simulators that there is an enable/disable pin that puts the output
stage in tri-state or receiving mode. The mechanism also tells S2ibis
how to test the part. If it is just an open sink without the tri-state
or input then the gnd/pwr clamps are not needed because they are
contained in the pullup or pulldown data. Sorry I misread open_sink
as open_source.

Best Regards,

"Henrik G. Madsen" wrote:
>
> Fred,
>
> Thanks for the input.
>
> As far as I can read the IBIS standard, 'Open_sink' and 'Open_drain' are the same, where the first one is the preffered type. Correct me if I'm wrong.
>
> It actually works to use the I/O_open_sink :-)
>
> I will use the I/O_open_sink model type in the .s2i file to get the correct VI curves, but change the modeltype back to 'Open_sink' in the final IBIS file to get the correct model type.
>
> /Henrik
>
> -----Original Message-----
> From: Fred Balistreri [mailto:fred@apsimtech.com]
> Sent: 26. november 2002 19:15
> To: Henrik G. Madsen
> Cc: ibis-users@eda.org
> Subject: Re: [IBIS-Users] s2ibis2 problem with 3-stateable OD drivers
>
> Hello Henrik, your information below says Open_sink not Open_drain.
> No matter, you may want to try I/O_open_drain (or sink) as the proper
> pin type.
>
> Best Regards,
>
> "Henrik G. Madsen" wrote:
> >
> > To me it seems that s2ibis2 do not support generation of open-drain models with tri-state outputs properly.
> > I'm using the Windows version, but I believe that the issue is of general nature.
> >
> > ********** From .s2i file
> > [Pin]
> > pad pad pad osoc2_od
> > -> D EN
> > D D D input
> > EN EN EN enable
> > VDD VDD VDD POWER
> > VSS VSS VSS GND
> >
> > [Model] osoc2_od
> > [Model type] Open_sink
> > [Polarity] Non-Inverting
> > [Enable] Active-low
> > *************
> >
> > The above will not generate the correct VI tables.
> >
> > By using the above info, s2ibis2 will generate spice simulations for
> > 1) 'Pulldown curve'
> > 2) 'Pulldown curve with output disabled'
> > but no 'Ground clamp' simulation.
> > I assume it then creates the IBIS PULLDOWN curve by subtraction the second curve from the first one (only for negative voltages).
> > The resulting IBIS model only has one VI curve, the modified PULLDOWN where the clamping has been subtracted. But it does not add the missing current by adding a 'Ground Clamp' curve.
> >
> > It seems that a correct result only can be obtained by removing the enable signal and run s2ibis2 with that, Or create the missing 'Ground Clamp' curve manually.
> >
> > Can it be true that s2ibis2 do not support OD-drivers with enable signal?
> >
> > _____________________________________
> > Henrik G Madsen
> > Sr. HW Engineer
> > Vitesse Semiconductor Corporation A/S
> > Ethernet Products Division
> > Hoerkaer 16, DK-2730 Herlev, DENMARK
> > Direct: +45 4485 5920
> > Phone: +45 4485 5900, Fax: +45 4485 5901
> > mail: hgm@vitesse.com
> > web: http://www.vitesse.com
> > _____________________________________
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> --
> Fred Balistreri
> fred@apsimtech.com
>
> http://www.apsimtech.com
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-- 
Fred Balistreri
fred@apsimtech.com

http://www.apsimtech.com
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