Subject: IBIS FAQ for the homepage

From: [email-masked] (Syed Huq)
Date: Wed, 26 Jul 95 11:20:15 PDT

IBISgurus,

As discussed earlier, we are in the process of putting together a
listing of IBIS FAQ's for the EIA IBIS homepage. I am attaching the 
initial listing of Q's and A's and I will need feedback, comments
and approval.

We can change the order or the contents of each FAQ and we may also
add more to this list.

Please post your comments, changes to the reflector so it can be 
approved.

I would like to receive all feedbacks/comments/changes BEFORE the
Aug11th IBIS teleconference so we can vote on this.

Best Regards,
Syed
National Semiconductor.

-------------------------------------------------------------------
 A compilation of IBIS related FAQ(Frequently Asked Questions). Issues 
 related to Modeling, Simulations, Support, Features and others are 
 addressed here.

1.0 What is this IBIS stuff anyhow ?
IBIS(Input Output Buffer Information Specification) is a method of providing
the Input/Output device characteristics through V/I data without disclosing 
any circuit/process information. It can be thought of as an Analog Behavioral 
Modeling Specification that can be used to model almost 99% of any 
semiconductor in the Industry today. IBIS is mostly used for transmission line 
analysis as well as Signal Integrity analysis. 

2.0 What is the "Golden Parser" ?

The "Golden Parser" is a shareware used to parse the model file to check if the 
file conforms to the IBIS specification. All model files need to pass the parser
before a model can be released on the Internet.  

3.0 Where can I find the IBIS Golden Parser ?

You may download a copy of the executable directly from vhdl.org(anonymous ftp 
site) under /pub/ibis/ibis_chk. To obtain a copy of the source code, 
send E-mail to: ??

4.0 Where can I find available IBIS models ?

All IBIS models released today resides in an anonymous ftp site at vhdl.org.
You may ftp to this site and change directory to /pub/ibis/models to find all
models. There are multiple ways of downloading these models from the Internet:

Using Mosaic:
URL: http://www/vhdl.org/pub/ibis

click on  'models'

Using FTP:
ftp to vhdl.org or ftp to 198.31.14.3
and login as anonymous
password can be your E-mail id
change dir using cd to

/pub/ibis/models

use ftp command 'get' to copy files.

Using Dial-up Modem:
Use any communication software on your PC
(Ex. QuikLink, Procomm, LapLink. Terminal(Windows) etc)

Dial: (415)335-0110

Login as guest
Password: just hit return

You will see the Welcome message from VHDL and it will
prompt for password again. Enter your E-mail id this time

Typical Modem setup:

Baudrate=upto 14.4
Databit=8
Stop=1
Parity=None
Flow=Xon/Xoff

You can download files using "kermit","zmodem" or "sz" etc

5.0 Can IBIS model best case, worst case models ?

Yes, by using the min, max current with the proper min, max ramp rates, the
Best, Typical and Worst case can be modeled.

6.0 Can IBIS model SSO(Simultaneous Switching Output) ?  

IBIS as a model, has all the parameters required to model an SSO event. These
are mainly the package inductance parameters and other associated parasitics.
Modeling an SSO event is more of a simulator issue than IBIS.

7.0 Why do we need to sweep to 2Vcc ?

IBIS models are meant to work on any simulator platform, SPICE or non-SPICE.
But on a SPICE platform, the simulation might not converge if the end points
are not specified. Most non-SPICE based simulators will do their own
extrapolation to get to the end point. So, to make the IBIS model function on
all platforms, that data needs to sweep to the full IBIS range, for example
2Vcc.

8.0 Can IBIS model GTO(Gradual Turn On) or Slew rate controlled outputs ?

IBISv2.1 can model RTC(Rise Time Controlled), GTO(Gradual Turn on) or Slew rate
controlled outputs. These are defined under [Rising Waveform] and [Falling
Waveform] keywords. See IBISv2.1 specification for more details.

9.0 Can IBIS model ground bounce ?

Yes, IBIS contains the the package parasitic information necessary to simulate
ground bounce. Even though the data is available within the model file, not all
simulators may be able to use it to simulate ground bounce. Refer to your
respective simulator for support. 

10.0 Can IBIS provide timing information ? ex.propdelays, skew etc

No, the present IBISv2.1 does not provide timing information.

11.0 Can IBIS model be used to measure propagation delays ?

IBISv2.1 does not support measurement of propagation delays. IBIS is mainly
used to simulate transmission lines and analyze signal integrity issues.

12.0 What type of Input/output structures are supported by IBIS ?

Following is a list of the output model types supported by IBISv2.1:

Input, Input_ECL, Output_ECL, I/O_ECL, I/O, I/O_open_drain, I/O_open_sink, 
I/O_open_source,Input_ECL, I/O_ECL, Terminator, Output, 3-state, Open_sink, 
Open_drain, Open_source

Refer to IBISv2.1 for a full explanation of the Input/Output structures.

13.0 How do I release an IBIS model to the Internet ?

North Carolina State University handles all IBIS model releases to the
Internet. Follow the procedure described below to release a model:
		
		PROCEDURE FOR SUBMITTING A MODEL TO
                        THE IBIS MODEL LIBRARY

                               January 6, 1994

                                Michael Steer
                            IBIS Model Librarian
             Department of Electrical and Computer Engineering
                    North Carolina State University
                    Raleigh, NC 27695-7911
                    phone: +1-919-515-5191
                    fax:   +1-919-515-3027
                    email: [email-masked]   (preferred means of communication)

Vendors and others are encouraged to submit IBIS models to the IBIS model
library.  The IBIS librarian maintains the IBIS models stored on vhdl.org
in the directory /pub/ibis/models .

  1.  Before submission models must be readable by the Golden
      Parser with out errors or warning messages being generated.

  2.  A submission should consist of the following:

      a.  A readme file ( named README.TXT ) including the following
 
          Name of Person Submitting:   XXXXXXXXXXXX
          Address:     XXXXXXXXXXXXXXXXXXXXXXXXXXXX
          Affiliation: XXXXXXXXXXXXXXXXXXXXXXXXXXXX
          E-Mail:      XXXXXXXXXXXXXXX
          Telephone Number: XXXXXXXXXXXXXXXXXXXXXXX
          Fax Number:       XXXXXXXXXXXXXXXXXXXXXXX
          Suggested Directory Structure XXXXXXXXXXX
            Structure for models

      b.  A Model Transfer Agreement Use the sample below) must be signed
          and mailed to the IBIS librarian < [email-masked] >.  The model
          transfer agreement must be MAILED to 
                    Dr. Michael Steer
                    Attn: IBIS
                    Department of Electrical and Computer Engineering
                    North Carolina State University
                    Raleigh, NC 27696-7911
          The above address is good for the post-office, Federal Express,
          Airborne, UPS etc. even though there is no street address.

          The model check-in procedure will not be finalized until
          this agreement has been received by the IBIS librarian.

      c.  All files should be in a single file before emailing to the IBIS
          librarian. Use one of the following four methods:
	
	  1. [ gnu tar AND ( uuencode OR mmencode ) ]
          2. [ tar AND compressed AND ( uuencode OR mmencode ) ]
          3. [ zip AND ( uuencoded OR mmencode'd ) ]
          4. [ zip ] 
             Note that zip'ing alone may result in problems due to non-ascii 
             characters.  You can obtain suitable programs for DOS as follows:

          ftp oak.oakland.edu
 login as anonymous
          binary                              // to put in binary transfer mode
          cd /pub/msdos/zip
          get pkz204g.exe                     // the zip archive create/extract 
                                                 program.  Run this program to
                                                 generate the required utilities
          cd /pub/msdos/compress
	  get comp430d.zip                    // Unix-compatible 16bit 
                                                 compress/uncompress utility
          cd /pub/msdos/decode
	  get qux01_91.zip                    // UUencode/UUdecode
   
          quit                                // finish up
 
      Expect an acknowledgement within two days.

  3.  When models are received:
         a. The following will be added to each IBIS file if not already
            present:

         [Disclaimer] IBIS Open Forum disclaims all warranties. See
         DISCLAIM.TXT in vhdl.org:/pub/IBIS/models for the full disclaimer.

         b. The IBIS models will be checked with the Golden Parser and if
            they parse successfully they will be accepted.

  4.   The IBIS models will be treated as confidential until they are
       publically released.  When new models are added an announcement will
       be made.

==============================================================================
   
                 IBIS Model Transfer Agreement

The under-signed submitter has submitted the following models to
the IBIS library (list model filenames)

------------------------------------------------------------------------------

------------------------------------------------------------------------------

------------------------------------------------------------------------------

The submitter authorizes inclusion of the submitted models in the model
library.

The model files will be provided as is except for the addition of the
following statement to each file:

        [Disclaimer] IBIS Open Forum disclaims all warranties. See
        DISCLAIM.TXT in vhdl.org:/pub/IBIS/models for the full disclaimer.

If the models were written as a work made for hire in the course of
employment, the Work is owned by the company/employer which must sign this
agreement in the space provided below.

Submitter's Signature and Date  _______________________________

Typed or Printed Name and Title _______________________________

Institution or Company          _____________________________________________

Authorization (if required)     _______________________________

Typed or Printed Name and Title _______________________________

Please Check
___________

                         ___
  Submitter's Own Work   |  |
                         |__|
                         ___
  Work done for Hire     |  |
                         |__|

14.0 It is rightly pointed out that the pulldown and pullup
characteristic for tristate outputs may be non-monotonic. The standard
says that this can happen in at most one place. The i-v characteristic
may then locally have a negative resistance. Will this not pose a
problem to simulators ?

The IBIS standard specifies that the pullup and pulldown curves
contain pullup and pulldown data ONLY, i.e. in the region where
the clamp diodes are active the current due to the clamp diodes must
be subtracted from the pullup/pulldown current.  This is where the
non-monotonic curves come from -- at the extremes of the I/V curves
where you are subtracting a large diode current from the combined
diode/on-state-IV curve.  In practice, a simulator sums the two
currents together (power clamp and pullup or gnd clamp and pulldown)
thereby making the result monotonic.

15.0 Is there a provision for specifying a pad or die resistance i.e
R_comp in addition to C_comp?

No.  The effects of a pad or die resistance are accounted for in the 
I/V curves.

16.0 The standard does not explicity specify the nature of the input
ramp in obtaining ramp rates. What should be the input rise time as
well as the high and low values of the input pulse?

IBIS does not provide an Input pulse specification for
deriving Ramp rates (and Waveform Tables).  A reasonable guideline is to
mimic actual conditions for which the device would be used.  Therefore 
it is probably better not to mandate a specific condition.  The voltage 
swing should be appropriate for the technology, e.g., 0 to 5V for CMOS 
and about 0 to 3V for TTL.  A signal faster than the expected Ramp rates 
is my preference, although a case could be made to provide a response 
that mimics the data book input ramps specified for timing tests.Possibly 
a 50 Ohm series resistance approximating the pulser source impedance and 
trace environment to the device input should be included.  However, since 
the actual thresholds are narrow (several 100 mV), the Ramp rates and 
Waveform tables should not differ significantly for any reasonable, 
appropriate Input.

					END

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From: [email-masked] ( Bob Ross)
Date: Thu, 27 Jul 95 18:33 PDT

Syed:

Great start on the Home page.  Regarding Question 2, I think "shareware"
is the wrong word and may even imply some privately developed code for
which a voluntary contribution is requested.  Rather, it is free, publically 
available executable code developed by contractors for the IBIS Open Forum.

Bob Ross,
Interconnectix, Inc.

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