Subject: V/I table rules not crystal clear

From: Matthew Flora <[email-masked]>
Date: Tue, 03 Nov 1998 09:07:37 -0100

All,

I noticed that the Golden IBIS Parser will issue an error if, in any V/I
table, the MIN column contain values, but the first or last entry of the
column is NA.  (The same is true of the MAX column.)

I hadn't remembered such a requirement, so I looked it up in the IBIS 3.1
specification.   The specifications seems to be poorly worded on this subject.

Here is the relevant excerpt from the IBIS 3.1 description of the [Pulldown],
[Pullup], [GND Clamp], [POWER Clamp] keywords does not 

     All four columns are required under these keywords.  However,
     data is only required in the typical column.  If minimum
     and/or maximum current values are not available, the reserved
     word "NA" must be used.  "NA" can be used for currents in the
     typical column, but numeric values MUST be specified for the
     first and last voltage points on any V/I table.  Each V/I
     table must have at least 2, but not more than 100, voltage
     points.

Note that in the following sentence, the subject is the typical column:

     "NA" can be used for currents in the typical column, but numeric
     values MUST be specified for the first and last voltage points
     on any V/I table.

So, my questions to the forum are:

1) What was the specification's intent here?
2) Does that intent match everyone's understanding of the rules?
3) Shall I draft a BIRD to change the wording so that this question won't
   arise again in the future?

Regards,
Matthew Flora
IBIS Open Forum Secretary
(425) 869-2320 PH
(425) 881-1008 FAX
[email-masked]
HyperLynx, 17641 NE 67th Court, Redmond, WA 98052 USA

---

From: "Muranyi, Arpad" <[email-masked]>
Date: Tue, 3 Nov 1998 10:18:00 -0800

Matthew,

The intent was this:

1)  If you make an IBIS model you must have at least typical data in the I-V

curve who's keyword is defined.  This was established so that when you are 
making a model from measurements and don't have skewed chips you should
still be
able to make a valid model.  In this case the min and max columns will be NA
all
the way through (including the last points), but the typ column will most
likely
have no NAs at all (even though it is not illegal).

2)  For practical reasons we also wanted to make sure that the endpoints of
the 
tables do not have NAs.  This is where things get confusing.  My
understanding 
is that if you have a min or max column with no data at all, those columns
are 
allowed to have NAs even on the end points.  It is only data tables with
data 
which are not to have NAs in the end points.

I went through the same problem years ago, and if I remeber correctly we
even 
discussed this in the Open Forum meetings, but nothing was done about it.
Maybe
you will have better luck rewording the spec...

Arpad
============================================================================
===

All,

I hadn't remembered such a requirement, so I looked it up in the IBIS 3.1 
specification.   The specifications seems to be poorly worded on this
subject.

Here is the relevant excerpt from the IBIS 3.1 description of the
[Pulldown], 
[Pullup], [GND Clamp], [POWER Clamp] keywords does not

Regards,
Matthew Flora