Proposal for treatment of BUG54...

In Friday's IBIS Forum, I took an AR to examine how the parser treats
IBIS files where all the min/max parameters are set to NA (rather than
just the min/max V-I curves). Recall that BUG54 was filed in order to
correct the parser's treatment of models missing a [Pullup] section and
max/min V-I curves. The parser currently shows warnings regarding the
inability of such a model to drive the buffer delay test load through
the specified Vmeas point.

The parser continues to give errors on the missing max/min V-I curves,
regardless of whether ramps, c_comp or voltage range min/max values
are present or absent. I have enclosed an additional example below.

Therefore, we may conclude that the parser is only looking for V-I curves
 in the min & max columns (for models without a [Pullup] section) to use
in determining whether the model can satisfy the buffer delay voltage
requirements.

To decide how to resolve BUG54, we need to decide how the parser should
treat the keyword "NA" for this case. The spec unfortunately allows two
interpretations of "NA," according to the two rules below:

     Rule 1) "NA" means "no data" -- no assumption is to be made as to
     the operation of the modeled device in those columns under those
     conditions. This is the intent behind using NA to entirely replace
     a column of V-I, t-V, ramp, c_comp or operating condition data.

     Rule 2) "NA" means "no explicit data" -- data is not given for
     this particular condition in this particular column, but the state
     of the device at this point is to be inferred from the surrounding
     context by the sim tool. This is the normal usage of NA, when
     mixed into a column of V-I or t-V data. This is also the reason
     behind prohibiting the use of NA as a starting or ending point in
     a column of data.

Currently, the parser checks V-I curves using Rule 2 above for models
where partial data is available in all three columns. Rule 1 is used
for most models where NA completely replaces V-I data in a min or max
column.

BUG54 was filed because the parser incorrectly applies Rule 2 for models
where the keyword [Pullup] is missing and entire V-I columns are
replaced by NA. For any other case where an entire column is missing,
Rule 1 is the only rule applied.

So, to "fix" BUG54, I would suggest simply eliminating the warning
messages and applying Rule 1 to all models without a [Pullup] section
and without min/max V-I curves. This makes the parser self-consistent
and also gives sim tool vendors the same flexibility about the treatment
of NA as they currently have. No additional cases or interpretation
would be required.

Any suggestions or advice? I will incorporate any consensus here into a
revised BUG54, which I will distribute for posting a week before the next
IBIS meeting (March 30).

Thanks!

- Michael Mirmak, Intel Corp.

|***********************************************************************
|
[IBIS Ver] 3.2
[File Name] bug54a.ibs
[File Rev] 0.0a
[Date] 05-March-2001
[Source] File created from specification
[Notes] Using the IBISCHK3 v3.2.5 & v3.2.6 parsers, the
                 following file will show two misleading warnings
                 related to the buffer delay fixture.
|
[Disclaimer]
    (C) Copyright 2001 Intel Corp.
    All rights reserved
    This model is for demonstration purposes only,
|
[Component] GENERIC_IBIS
[Manufacturer] Intel Corp.
|
[Package]
| typ min max
R_pkg 6.0mO NA NA
L_pkg 5.0nH NA NA
C_pkg 1.0pF NA NA
|
|
[Pin] signal_name model_name R_pin L_pin C_pin
1 TestSignal1 TestModel1
|
|************************************************************************
|
[Model] TestModel1
Model_type I/O_open_sink
|Model_type I/O
Polarity Non-Inverting
Enable Active-Low
|
Vinl = 800mV
Vinh = 2.0V
|
Cref = 0F
Rref = 25ohms
Vref = 5.0V
Vmeas = 2.5V
|
C_comp 5.00pF NA NA
|
[Temperature Range] 27.00 NA NA
[Voltage Range] 5.0V NA NA
|
|[Pullup]
|| voltage I(typ) I(min) I(max)
||
| -5.0000 0.0m NA NA
| -4.0000 0.0m NA NA
| 0.0000 0.0m NA NA
| 5.0000 0.0m NA NA
| 10.0000 0.0m NA NA
|
|
[Pulldown]
| voltage I(typ) I(min) I(max)
|
  -5.0000 -40.0m NA NA
  -4.0000 -39.0m NA NA
   0.0000 0.0m NA NA
   5.0000 200m NA NA
  10.0000 400m NA NA
|
|
[GND Clamp]
| voltage I(typ) I(min) I(max)
|
  -5.0000 -3900.0mA NA NA
  -0.7000 -80.0m NA NA
  -0.6000 -22.0m NA NA
  -0.5000 -2.4m NA NA
  -0.4000 0.0A NA NA
   5.0000 0.0A NA NA
|
[Power Clamp]
| voltage I(typ) I(min) I(max)
|
  -5.0000 4450.00m NA NA
  -0.7000 95.0m NA NA
  -0.6000 23.0m NA NA
  -0.5000 2.4m NA NA
  -0.4000 0.0m NA NA
   0.0000 0.0m NA NA
|
[Ramp]
|variable typ min max
dV/dt_r 2.20/1.06n NA NA
dV/dt_f 2.46/1.21n NA NA
R_load = 300ohms
|
|
|************************************************************************
[End]

 
Received on Mon Mar 5 15:00:05 2001