Re: BIRD #61

Fred Balistreri wrote:

> I passed some comments to Steven Peters about the general receiver bird.
> Steven thought
> it would be helpful to express those comments on the ibis reflector to
> get feed back. Here is the jest of my comments.
>
> The current bird will require eda vendors to essentially measure slope
> to determine delay. My idea would be to provide device voltage transfer
> information. That is vout as a function of the controlling vin. In this
> way there is no need to specify delay as a function of slope. The delay
> is measured at the output as it attains a high or low. Hystersis
> information can be added as a function of low to high or high to low.
> This may greatly simplify the spec and more importantly make it
> easier for EDA companies to implement.

I think that this actually addresses the subject of BIRD #61 instead,
so I've changed the 'Subject:' to match. #62 just attempts to capture
in IBIS the same specification semantics that already exist in standards
such as SSTL and HSTL so that there is common ground between the SI tools
and device timing specs.

WRT using vout <= f( vin ) semantic, the problem is that this is not
a static function. The whole point is that it's time-sensitive in
some pretty nonlinear ways. We had a go at characterizing input
delays using algebraicly and weren't happy with the results, so we
fell back on the IBIS tabular strategy.

That doesn't mean that there isn't some clever way to do it more
concisely; it just means that the BIRD's authors weren't smart
enough to find it. Maybe one of the other listmembers will fare
better.

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