Subject: BIRD31.2 - Mated Models

From: Stephen Peters <[email-masked]>
Date: Mon, 29 Apr 1996 12:57:21 -0700

Hello Bob:

     A quick comment on the Tedge_rate parameter.  I think the allowable
values for Tedge_rate should also include 'NA' - not available.  If the
information is not available, I feel it should be stated explicitly, not by
entering a value of zero.  Anyway, that is my preference.

                   Regards,
                   Stephen Peters
                   Intel Corp.

>>>> excerpt for BIRD follows follows

|==============================================================================
|     Keyword:  [Define Package Model]
|    Required:  Yes
| Description:  Marks the beginning of a package model description.
| Usage Rules:  If the .pkg file contains data for more than one package,
|               each section must begin with a new [Define Package Model]
|               keyword.  The length of the package model name must not
|               exceed 40 characters in length.  Blank characters are
|               allowed.  For every package model name defined under the
|               [Package Model] keyword, there must be a matching [Define
|               Package Model] keyword.
|------------------------------------------------------------------------------
[Define Package Model]     QS-SMT-cer-8-pin-pkgs
|
|*=============================================================================
|*     Keyword:  [Define Mated Model]
|*    Required:  Yes
|*2  Sub-params:  Tedge_rate, Cpad_1, Cpad_2
|* Description:  Marks the beginning of a mated model description.
|* Usage Rules:  If the .mmf file contains data for more than one mated model,
|*               each section must begin with a new [Define Mated Model]
|*               keyword.  The length of the mated model name must not
|*               exceed 40 characters in length.  Blank characters are
|*               allowed.
|*  
|*2               The Tedge_rate is as a required subparameter defining the
|*2               the minimum time edge rate for which the mated model is
|*2               considered accurate under test fixture conditions.  A more
|*2               detailed mated model topology would be preferred if the edge
|*2               rate were smaller.  The Tedge_rate subparameter may serve
|*2               to produce a warning that the simulations are being done
|*2               outside of the mated model performance range.
|*2               
|*2               A numerical value must be defined.  It is the input pulse
|*2               rise time defined between the 20% and 80% points.
|*2               This value will be the minimum value where the signal line
|*2               "impedance" is within 10% of the simulated impedance.  This
|*2               impedance parameter is the dynamic ratio at the mated model
|*2               input voltage to input current over time under the condition
|*2               that the signal line has a source and load termination of
|*2               of 50 ohms and all other lines are grounded.  A value of 0
|*2               is permitted, and would serve as an indication that no
|*2               performance limit is available.  However, if the model is 
|*2               suitable for all edge rates, use a very small, non-zero
|*2               value such as 1e-15 seconds.
|*2
|*               The Cpad_1 and Cpad_2 subparameters are optional and define 
|*               default pad capacitances at sides 1 and 2 of the mated model.
|*               The values default to 0 pF if omitted.  However, in all cases 
|*               the simulator may override the default values based on
|*               actual geometrical pad dimensions.               
|*2
|*2 Other Notes: The mated model extends to the physical surfaces of the
|*2              structure in the mated configuration.  For example, the
|*2              the printed circuit board fingers of an edge card connector
|*2              that extend into the connector are included in the mated
|*2              model electrical description.  The Cpad_1 and Cpad_2 sub-
|*2              parameters are optional default extensions for pads outside
|*2              the mated model physical dimensions.
|*------------------------------------------------------------------------------

---

From: [email-masked] ( Bob Ross)
Date: Mon, 29 Apr 96 14:27 PDT

To Arpad, Stephen and IBIS committee.

In every case in IBIS, the subparameter syntax "XXX = yyy" requires that
"yyy" be numerical.  I do not feel it is necessary to make a syntactical
exception which could create confusion elsewhere.

One option is to make Tedge_rate optional.  The omission of the subparameter
is effectively identical to "Tedge_rate = NA".  I would prefer this option.
Then "Tedge_rate = 0" can mean no limit.

Another alternative is to develop another syntax such as

[Define Mated Model]   Tedge_rate

Tedge_rate is a numerical value or NA.  Again I am sensitive to setting
up unnecessary deviations from existing conventions.

Bob Ross
Interconnectix, Inc.

> Text item: 

> I second that, zeroes (and infinites) are dangerous numbers some times...

> Arpad
> ==============================================================================
> Hello Bob:

---

From: Stephen Peters <[email-masked]>
Date: Mon, 29 Apr 1996 14:54:18 -0700

Hello Bob:

   Ok, you win <grin>.  Seriously, I think this is a valid argument
for making Tedge_rate an optional parameter.  HOWEVER, it should be
clearly stated that if the parameter is missing, the Tedge_rate 
information is unavailable and the user can make no assumptions about
the suitablility of the model for high frequency simulations.

                 Regards,
                 Stephen

Bob Ross
Interconnectix, Inc.