Re: BIRD 42.3

C. Kumar wrote:
> Bob Ross wrote [attribution restored -- dcs]:
> > D. C. Sessions wrote [attribution restored -- dcs]

> I have not also had time to respond to bird 42.3. Your one specific example of zero current does not detract away the utility of the original contention for current waveforms in bird 42.3.

Speaking as an I/O designer, we work *very* hard to avoid crowbar
current.
This is not just a matter of a specific example; it's the majority case.
IMNSHO, an extension to the standard which *only* addresses cases with
major crowbar current is best described as "one specific example."

Parsimony dictates that we *not* extend the standard willy-nilly;
if there are two possible extensions, one of which is only marginally
applicable to a rare condition and another which addresses both that
*and* the majority case, the latter is always to be preferred.

> IBIS metholody is a general black box methodology and should not be confined to the vagaries of specific technologies.

True enough, but its relevance escapes me..

> Adding the current waveforms is relatively minor matter since during the spice runs the data is easily available. Redundacy in some cases does just not justify keeping out the data.

I could name a thousand "minor matters" which might be nice to have in
one-of-a-kind
situations. We're not adding them because their net impact on the
usefulness of the
standard is *negative*. Repeating what I wrote in the first place:

> > IMNSHO, this effect is far more important than the
> > (extremely rare) case of major crowbar current,
> > and any solution to this will necessarily also take
> > care of those few instances where crowbar current
> > is actually significant.

Real-world, IMMEDIATE applications such as SSTL can't be properly
modeled right now without addressing the case I presented. (look
back at the time-domain behavior and see what it implies when
applied to a line terminated to Vddq/2) This isn't something we
can blow off by pretending it's a rare case. We *need* to
address the issue. When we have, we'll also have a solution to
the (rare) crowbar-current problem as a freebie.

So what are we going to do?

-- 
D. C. Sessions
dc.sessions@tempe.vlsi.com