Subject: About WARNING of ibischk2

From: Akihiro Takegama <[email-masked]>
Date: Tue, 31 Mar 1998 22:08:55 +0900 (JST)

To: IBIS-users,

  Hello, I'm making the IBIS model. But I am confused at ibischk.
 Could you support me ?

  I have one question.

  1 ) I made the IBIS model within "Rising Waveform" and "Falling
     Waveform" and I ran the ibischk2. But many warning appeares
     it's IBIS model, which like as below.
      Could you please tell me how to calculate the value [3]. ?
      
- ----------------------------------------------------------------------------
WARNING - Model 'inout': MIN AC Rising Endpoints ( 0.74V,  3.00V) not within
                                                   -------------
                                                        [1]

          0.045V (2%) of ( 0.95V,  3.00V) on VI curves for 50 Ohms to 3V
          -----------    ----------------
             [2]               [3]
- -----------------------------------------------------------------------------

 - Regards,
    A.Takegama

    ************************************
    *   Name   : Akihiro Takegama      *
    *   E-mail : [email-masked]  *
    *   Corp.  : Texas Instruments     *
    ************************************
------- End of forwarded message -------

---

From: Chris Rokusek <[email-masked]>
Date: Tue, 31 Mar 1998 10:01:46 -0800

Akihiro,

The ibishk2 program is checking the first and last point of your Rising
and Falling AC Waveforms against the DC VI curves and given test load
(50 Ohms).

For your case the message indicates that the first point given in the
Rising Waveform table is .74V.  

If you were to plot the intersection of a 50 Ohm to 3V load line (slope
= 50 V/I) and the given DC VI curve you would see that they interesect
at .95V (this is fist value in [3] below).

So since 

     abs(.95 - .74) > 2% * (3 - .74)
               .21  > .045

The checker will print a warning.

The reason for the check is that the first and last points of the AC
waveforms are supposed to be the stable DC value when driving the given
load.

Chris Rokusek
Viewlogic