Incremental fault dictionary

• US 20030046608A1
• Filed: 09/05/2001
• Published: 03/06/2003
• Est. Priority Date: 09/05/2001
• Status: Active Grant

• Current Assignee: Cadence Design Systems Incorporated (Cadence Group)
• Original Assignee: International Business Machines Corporation
• Inventors: Huisman, Leendert M., Mechler, Thomas F., Rosner, Raymond J., Pastel, Leah M.P., Heaberlin, Douglas C., Bartenstein, Thomas W., Richard, Glen E.
• Granted Patent: US 6,675,323 B2
• Time in Patent Office: Days
• US Class Current: 714/29
• CPC Class Codes: G06F 11/2252 using fault dictionaries

Abstract

An incremental fault dictionary in which the diagnostic simulation results of current tests are stored for future use. Diagnostic simulation results are incrementally added to the fault dictionary, and information in the incremental fault dictionary is used to avoid expensive redundant fault simulations. The size of the incremental fault dictionary is maintained within user definable bounds by identifying and deleting faults that need not be maintained in the incremental fault dictionary. The incremental fault dictionary beneficially provides more accurate and faster diagnostics than a typical prior art diagnostic fault simulation.

Claims

1. A diagnostic method in which diagnostic simulation results of current tests are stored in an incremental fault dictionary, and information in the incremental fault dictionary is used to avoid expensive redundant fault simulations, comprising:

for faults associated with a failing device, perform fault simulations of failing patterns, while not repeating fault simulations of faults that have already been simulated for any of the failing patterns and whose corresponding results are stored in the incremental fault dictionary, and complete the current diagnosis for the failing device, and add the diagnostic simulation results for the current diagnosis to the incremental fault dictionary if not already stored in the dictionary.

2. The diagnostic method of claim 1, further including analyzing the logical structure of the failing device and identifying those possible faults that could have caused any or all of the failing patterns.

3. The diagnostic method of claim 1, wherein faults are taken from a master fault list and from possible auxiliary fault lists that are produced during previous diagnoses.

4. The diagnostic method of claim 1, further including identifying less needed faults or fault/pattern pairs and removing the identified less needed faults or fault/pattern pairs from the resulting incremental fault dictionary if the resulting incremental fault dictionary has become too large.

5. The diagnostic method of claim 4, wherein criteria for identification and removal from the incremental fault dictionary include a count of the number of times a fault is encountered, a fault'"'"'s last date of use, the amount of space required to store a particular fault/pattern entry, and the cost associated with regenerating that entry if needed again.

6. The diagnostic method of claim 1, including storing in the incremental fault dictionary the physical locations of the nets that are called out in the diagnosis, as well as the correspondence between the logical and physical netnames.

7. The diagnostic method of claim 1, including subdividing the incremental fault dictionary based upon the physical nature of the net/pins in a diagnosis.

8. The diagnostic method of claim 1, including entering in the incremental fault dictionary an entry that a simulated fault produced no fails, or that a fault/pattern combination produced no fails for that pattern.

9. The diagnostic method of claim 1, wherein a fault is identified as hyperactive and removed when its associated fault machine size becomes too large, and a permanent entry is entered in the incremental fault dictionary which indicates that that fault is hyperactive on that pattern.