Re: Vmeas

"Kern, Frank" wrote:
>
> While on this topic...
>
> Previous generations of IBIS forced Vinh, Vinl and Vmeas parameters to be
> invariant across corner conditions. I build AGTL+ models where these
> parameters vary with respect to Vtt, therefore across corners [i.e. Vtt +/-
> 10%, Vmeas =(2/3)*Vtt, Vih = Vmeas + 200mv, Vil = Vmeas - 200mv]. To keep
> valid measurement points across the skew, I have to create separate model
> files for fast, slow and typical conditions. Does the new IBIS spec provide
> flexibility to define Vinh, Vinl, and Vmeas for each corner?

[Model Spec] has made things a little bit better, but the real answer is that
we're working on it. In particular, have a look at BIRD 62 and BIRD 63.

> -----Original Message-----
> From: D. C. Sessions [mailto:dc.sessions@vlsi.com]
> Sent: Tuesday, October 05, 1999 10:24 AM
> To: ibis-users@eda.org
> Cc: Amir Shavit (r56010); Udi Barel (r51365)
> Subject: Re: Vmeas
>
> "Amir Shavit (r56010)" wrote:
> >
> > Hi,
> > I'm cuurrently working on an ibis model. I'v encountered some problem
> > with this parameter since it is different for rising and falling time. I
> > don't know what it should be equal to, since there are 2 different
> > values.
> > Thanks for your answers
> > Amir Shavit
> > Motorola Semiconductors Israel
>
> Shalom Amir.
>
> I'm a bit puzzled about the "different rising and falling" cases.
> Are the defined timing points for the device you're working with
> actually specified differently for the two directions? The reason
> I ask is because it's very hard to have a setup time, for instance,
> which is different for rising and falling edges.
>
> Vmeas _should_ be the point at which the characterized ("data sheet")
> timing is defined. This is usually 1.5v for LVCMOS, but is sometimes
> 50% of supply (a better way), 40% of supply (PCI and AGP), or an
> external threshold (SSTL, HSTL, GTL, Rambus, etc.)
>
> --
> D. C. Sessions
> dc.sessions@vlsi.com

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