Browse Prior Art Database

Fault-Simulation Diagnostics

IP.com Disclosure Number: IPCOM000100881D
Original Publication Date: 1990-Jun-01
Included in the Prior Art Database: 2005-Mar-16
Document File: 2 page(s) / 60K

Publishing Venue

IBM

Related People

Dubler, JF: AUTHOR [+3]

Abstract

Disclosed is a method to process fault-simulation results into data that can be very useful in diagnosing failing cards and boards with a "guided probe" tester. The method assumes the fault simulator operates in a mode which simulates all "fault machines" for the entire set of test patterns. The fault simulator should produce signal activity for all potential probe points for the "good machine" and all "fault machines". "Fault machines" may represent traditional stuck-at-one and stuck-at-zero faults or other faults, such as short faults and delay faults.

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Fault-Simulation Diagnostics

       Disclosed is a method to process fault-simulation results
into data that can be very useful in diagnosing failing cards and
boards with a "guided probe" tester.  The method assumes the fault
simulator operates in a mode which simulates all "fault machines" for
the entire set of test patterns. The fault simulator should produce
signal activity for all potential probe points for the "good machine"
and all "fault machines".  "Fault machines" may represent traditional
stuck-at-one and stuck-at-zero faults or other faults, such as short
faults and delay faults.

      This invention organizes this fault-simulation data into a
"guided probe map".  The map consists of probe point measurements,
and recommended next probe point positions dependent on all previous
measurements.  The map has an implicit order in which probe
measurements must be made.  A path through this "guided probe map"
ends when only one of the simulated "fault machines" could have the
observed probe measurements, or when further probing will not isolate
the fault any better (an indication of poor test patterns).

      The key to this invention is the algorithm used to quickly
isolate faults.  Parallel probe measurement data and past probe
measurement data for the entire pattern set are used to select the
next best probe point. Any probe point set of pattern responses
typically contain many "fault machine" deviations from "good
machine".  Most often the devi...