accuracy BIRD

The IBIS Accuracy Subcommittee has been considering submitting a new BIRD
that would allow for a wider variety of golden waveforms to be included in
an IBIS datasheet (model). Right now these new golden waveforms would
correspond to the additional test loads described in section 3 of the IBIS
Accuracy Specification, but we will certainly be adding more test loads to
the list as we examine different kinds of I/O buffers and their associated
electrical behavior. At the 2/26 IBIS Users Group conference call, Bob
Ross suggested we run this by the IBIS reflector to solicit your input, so
here it is. The two main questions are:

1) Is it necessary to describe the test loads in a machine-readable
fashion, similar to the distributed package model and EBD options already
present in IBIS? Or should we opt for the more simple approach of adding a
waveform with comments describing the test load?

2) How does one distinguish between a golden waveform (w/ package) and a
regular old VT table (w/o package) in IBIS?

For those of you who were not at the DesignCon99 Summit, the IBIS Accuracy
Subcommittee presented a two-stage approach to documenting the correlation
results of an IBIS datasheet. Both stages involve embedding a golden
waveform, derived from SPICE, into the IBIS datasheet. The semiconductor
vendor can correlate the lab data to these golden waveforms and report the
correlation results in the "accuracy trailer," a comment section appended
to the IBIS datasheet. Using these same golden waveforms, the user can
correlate behavioral simulations and take up any significant discrepancies
with the simulator vendor. Question 1 above refers to automating the
second step of the correlation process. Of course, the user can always
capture the test load manually using the simulator's schematic capture
tool.

Greg Edlund
Advisory Engineer, Critical Net Analysis
IBM
3650 Hwy. 52 N, Dept. HDC
Rochester, MN 55901
gedlund@us.ibm.com
Received on Thu Mar 11 15:29:40 1999