Re: BIRD #61 -- Characterization of Receivers

D. C.,

> > > | An example table showing how receiver delay varies vs. overdrive.
> > > | Note the use of the reserved word INF.
> > > |
> > > [Receiver Delay]
> > > Start_point = 0.8v
> > > Slope = 1v/1ns
> > > End_point TABLE
> > > |variable typ min max
> > > 1.4 INF 7.0ns INF
> > > 1.5 INF 5.0ns INF
> > > 1.51 INF 3.0ns 10.0ns
> > > 1.53 7.0ns 0.0ns 7.0ns
> > > 1.55 2.0ns 0.0ns 1.0ns
> > > 1.6 0.0ns 0.0ns 0.0ns
> > > 1.7 0.0ns 0.0ns 0.0ns
> > > 2.0 0.0ns 0.0ns 0.0ns
> > > 2.1 0.1ns 0.1ns 0.1ns
> > > 2.5 -0.2ns -0.1ns -0.5ns
> >
> > Often, interpolation/extrapolation is used when trying to look up values
in
> > tables. When INF appears in the table, doesn't it present a discontinuity
in
> > the data? One of the examples given showed a delay delta of 7.0ns at
1.53V
> > and INF at 1.51V. What would the delta delay be at 1.52V? Where is the
elbow
> > in the curve? Is this simply a case of the table not having enough data
> > points?
>
> I don't see how you could use the data from the tables directly, thus
> interpolation is irrelevant.

I thought we are supposed to use the delay deltas in the table to adjust the
receiver's propagation delay. So using the example above (from the text of
the BIRD), if the rising edge at the buffer's input rises to a final voltage
of 1.55v, then Tco must be adjusted by 2.0ns. Correct?

However, if the rising edge at the buffer's input rises to a final voltage
of 1.54v, then Tco must be adjusted by a value interpolated between 7.0ns at
1.53v and 2.0ns at 1.55v. Correct?

Great. Now suppose the rising edge at the buffer's input rises to a final
voltage of 1.52v. Will the output switch? If so, what adjustment must be
made to Tco?

I believe the BIRD needs to spell this out.

Cheers,
Matthew Flora
IBIS Open Forum Postmaster
(425) 869-2320 PH
(425) 881-1008 FAX
mbflora@hyperlynx.com
HyperLynx, 14715 NE 95th Street, Redmond, WA 98052 USA
Received on Thu Aug 19 11:48:10 1999