Re: Proposed Golden IBIS Parser checks

Hello Matthew, D.C.:

   Comments below

        Regards,
        Stephen
> D. C.,
>
> >> Proposed enhancements:
> >
> >> 2) Generate at least a warning if the Pullup or Pulldown V/I table
> >> indicates that current is always flowing in one direction. In other
> >> words, the V/I table does not have an entry with zero current or, by
> >> interpolation, the current is never zero in the range of the voltages
> >> listed.
> >>
> >> I think a warning should be generated even if the current would be zero
> >> when extrapolated to a voltage beyond those listed in the table because
> >> I believe that V/I tables should be complete and should not force a
> >> simulator to guess values and, to me, extrapolation beyond the voltages
> > listed in the table is a guess.
> >
> >If I understand you correctly, you would insist that the tables
> >go at least to the zero-current intercept point. Thus, for an
> >1.5v device with a weak pullup to 5.0v you'd have the tables go
> >at least to 5v so as to catch the intercept?
>
> In a word, yes. If you have a 1.5v buffer which is active all the way up to
> 5v, then it's behavior needs to be described. I thought V/I tables are
> supposed to show the behavior of the device in its active region, and perhaps
> a bit beyond its active region. I thought that is why the spec suggests
> generally spanning the voltages between -Vcc and 2Vcc.

Actually, the -Vcc to 2Vcc requirement comes from the fact that this is the
maximum signal swing on an unterminated transmission line. If the output
swings 0 - 1.5v then the maximum voltage on the output would be -1.5v to 3.0v.
However, if the part is intended to live in a 5V signaling environment then
the V/I curves ought to to go from -5v to 10v.

   You know... this is really a defect in the spec. V/I table endpoints
should be determined not by VCC, but by output swing, as described above.
I feel a bird comming on....

>
> >> 4) Related to a topic recently discussed on the reflector, I suggest that
> >> an error be generated if a differential pin (a pin referenced in the
> >> [Diff pin] section) is connected to one of the reserved models (POWER,
> >> GND, or NC).
> >
> >This would barf on RS-423
>
> I am not familiar with RS-423. Does it have one or more pins whose voltage is
> to be taken differentially to POWER or GND?
>
> Cheers,
> Matt
Received on Wed Nov 4 15:29:17 1998