Subject: Bird 6, Differential signal spec, From Kellee Crisafulli

From: Kellee Crisafulli <[email-masked]>
Date: 21 Jan 94 03:35:28 EST

From: Kellee Crisafulli

To: Bob Ross and fellow IBIS members

Re: BIRD 6 (differential pin spec proposal)

Bob it is really nice to see all the activity from you.  This is another
great start on an IBIS improvment.

I have read your BIRD and have the following concerns:

1) The use of the vpp term to indicate the threshold voltage seems like a
   good idea, however the vpp label is used alot for programmable devices
   to indicate a programming supply pin and I am concerned about confusion
   factor at semi-conductor houses.  How about "vdiff" or something
   similar?

2) Real output buffers will have pin to pin skew between the non-inverting
   and inverting pins.  It seems like this could be significant factor for
   proper modeling at higher speeds.  I say could because I have little
   experience with differential mode systems.  Do you think we need to
   consider a delay term with min, typ, max ?  Would any of the Semiconductor
   vendors care to comment on this (National, TI etc)?

3) Should we consider using the POLARITY specification that already exists
   instead of the negative voltage to indicate polarity?  e.g. we could require
   that both pins have either inverting or both pins have non_inverting polarity
   and only except positive diffential threshold voltages.

Great start Bob!

Kellee ..