Re: BIRD58 discussion continued

Greg:

You raise several good points. My response is in upper case
in your text. Thank you for your input.

Bob Ross
Mentor Graphics

Subject: BIRD58 discussion continued
Date: Fri, 26 Mar 1999 17:10:50 -0600
From: gedlund@us.ibm.com
To: ibis@vhdl.org

IBIS Folks,

A thought occurred to me during today's BIRD58 discussion during the
Open
Forum call. What happens when a user gets an IBIS datasheet for a
multi-stage driver but isn't aware that the simulator does not use the
related keywords?

THE SIMULATOR WILL PROBABLY REPORT AN ERROR. SO THE USER MUST CHANGE
THE MODEL. THE USER THEN SHOULD BE AWARE THAT THE RESPONSE IS JUST
AN APPROXIMATION.

The user may get bogus simulation results and not know
it until he or she has failing hardware on the test floor. Now, you can
say that the user should be better educated, and that's true. Education
is
an across-the-board problem for users and modeling engineers. However,
we
might be allowing an opening for IBIS to get a black eye by allowing for
top-level data to exist under the model statement for a multi-stage
driver
. If the data is there, it may be used.

I think I understand the simulator argument; simulator vendors that
don't
support multi-staged drivers don't want to hurt their sales, right? But
unless you pop up a window that tells the user, "You're about to use an
IBIS datasheet for a multi-stage driver and we don't support this," the
user may unwittingly be taking on a very big risk. It just seems to me
that the most responsible thing to do is to make IBIS itself idiot-proof
in
this respect by not allowing IV curves in the top-level model. VT
tables
are great; they can be used for correlation.

YOU MAY BE CORRECT. HOWEVER, WE MAY NEED THE IV TABLES TO PRODUCE THE
CORRELATION RESPONSE INTO THE GIVEN TEST LOAD.

I'm sure this issue was discussed prior to my involvement, so I
apologize
if I'm trying to resurrect something that was already settled. I'm not
sure I totally understand the ramifications of what I'm saying here, but
I
suspect it might mean holding up IBIS 3.2 and the parser if we actually
did
what I'm suggesting? In that case, I'm sure this won't be a very
popular
posting :-(

WHAT YOU ARE STATING WOULD CHANGE VERSION 3.2 AND ALSO THE PARSER. IT
WOULD ALSO IMPACT SOME EXISTING IBIS MODELS.

Greg Edlund
Advisory Engineer, Critical Net Analysis
IBM
3650 Hwy. 52 N, Dept. HDC
Rochester, MN 55901
gedlund@us.ibm.com
Received on Mon Mar 29 18:19:57 1999