Subject: Re: IBIS FAQ for the homepage

From: Will Hobbs <[email-masked]>
Date: Tue, 08 Aug 95 12:08:00 PDT

Text item: 

Syed,

Thanks a lot for putting this together. I have a couple of changes to suggest. 
My comments appear below. I've deleted those things for which I didn't have 
comments. I also added a question about monotonic data and one about becoming an
active IBIS participant.

Will

2.0 What is the "Golden Parser" ?

* The "Golden Parser" is a program called ibis_chk that parses the model file to
verify that the file conforms to the IBIS specification.  All model files must 
pass the parser before a model can be released on the Internet.

3.0 Where can I find the IBIS Golden Parser ?

The parser is freely available in object code format for many platforms, and can
be downloaded via anonymous ftp from the vhdl.org BBS (198.31.14.3).  It resides
under the /pub/ibis/ibis_chk directory.

The Golden Parser source code is also available from the EIA IBIS committee for 
a fee.  In addition to checking syntax, it creates data structures from model 
data that simulators can use.

There are three options for licensing the IBIS Golden Parser source code,
V2.1, depending on your membership status in the IBIS committee of EIA:

1) If you are a current member of the IBIS committee, you can license the
parser source for an additional $250.00
2) If you are not a member, but would like to be, you can join the committee
and license the parser source for a total of $750
3) If you are not a member, and do not wish to become a member, you can
license the source for $500.

In any case, submit a request to:

     EIA
     2500 Wilson Blvd.
     Arlington, VA 22201
     (703) 907-7545 (phone)
     (703) 907-7501 (fax)
     
Enclose a check in the appropriate amount made out to EIA.  EIA will take
care of distributing the source.

7.0 Why do we need to sweep to 2Vcc ?

 >>> In addition to comments already submitted on this item, I would add:

Simulation accuracy is greatly enhanced by the "beyond-the-rail" data.  
Overshoot and undershoot generally fall within this range, and the range 
encompasses the forward-biased regions of protection diodes often used on 
buffers.

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.

Add:  The waveform tables can also serve as "golden waveforms" to check 
simulator accuracy, since the load conditions that produced the tables are 
specified. That is, the simulator should produce these waveforms when the model 
is connected to the specified loads.

10.0 Can IBIS provide timing information? E.g., propagation delays, skew, 
etc.?

11.0 Can IBIS model be used to measure propagation delays through IC's?

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

>> A space is needed before Possibly in the middle of the second paragraph 
below.

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.

17.0  Can IBIS handle devices whose output is non-monotonic?

IBIS can handle non-monotonic data.  The parser will detect such data and issue 
a warning in the possibility the data is in error, but will correctly parse the 
data.  Whether a given simulator will treat the data correctly is a question 
left to simulator vendors to answer.

For problems in modeling I/O buffers that IBIS doesn't adequately handle, the 
IBIS Open Forum (a.k.a. the EIA IBIS Committee) is always trying to extend IBIS 
to be more useful and has developed an excellent track record and set of 
processes to move the standard forward without harming backward compatibility. 

18.0 How do I become an active participant in IBIS activities?

To participate in IBIS discussions, send your email address to 
[email-masked] (198.31.14.3). You will be added to the IBIS reflector, 
which is a mail group used by IBIS partipants to exchange ideas and data. 
Notices of upcoming teleconferences, agendas, and meeting minutes are also 
distributed through the IBIS reflector.

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Cc: [email-masked]
Subject: IBIS FAQ for the homepage
To: [email-masked]
From: [email-masked] (Syed Huq)
Date: Wed, 26 Jul 95 11:20:15 PDT
:38:07 -0700
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