Re[2]: V/I table checking (from Kellee Crisafulli)

Don, et al,

This has been referred to as an emergency BIRD, which has to be ratified. The
BIRD hasn't been generated yet, and the change to the parser will have to be
benign (i.e., warning, not error). The issue is that this is a common pitfall,
and several feel we need to do something about it quickly.

Will

Howdy,

I'm glad you guys are working this issue. Please remember that it takes an
accepted BIRD to change the parser. I thought I read about someone editing the
parser on Monday (!?). That's not going to happen, right?

Donald Telian
___________________________________________________________

To: Jon Powel, Arpad, IBIS commitee
From: Kellee Crisafulli
Re: method to determine if V/I table is valid

Good point Jon and Arpad.

I had negelected to considered noise from systems where the data is being
sampled with a data acquisition system. (oops)

Several things make it difficult to test for the wrong sign:
  - The data can change direction and be valid.
  - Only 2 points are required to have a valid table.
  - No particular voltage points are required.
    (there may or may not be data points at VCC or ground).

I have a new simplified method based on Jon's suggestion that should also
-work
with Arpad's data:

For each V/I table:
  1) Find the minimum and maximum voltage points (Vmin, Vmax) in the table.

  2) IF:The TYPICAL current corresponding to Vmax is less than the TYPICAL
        current corresponding to Vmin than the table is assumed to have
        decreasing current.
     ELSE: The table is assumed to have increasing current.

  3) Verify that:
        - Pullup V/I table has decreasing current
        - POWER_clamp V/I table has decreasing current
        - Pulldown V/I table has increasing current
        - GND_clamp V/I table has increasing current

  4) If any table moves in the wrong direction flag as an error

  5) Another test we could consider is if the currents at Vmin and Vmax
-are equal
     then assume the data is a single point and thus invalid. (This may
-already be tested
     I don't recall).

I would still like to get agreement on this by Friday if possible.

Here's hoping this IBIS_CHK egg is not broken,scrambled, or stolen by
-the big bad wolf.
Have a great day... Kellee
Received on Wed Mar 16 16:27:13 1994