Signature compression register instability isolation and stable signature mask generation for testing vlsi chips
AssigneeInternational Business Machines Corporation
InventorsFranco Motika, Raymond J. Kurtulik, John D. Parker
Life of this patent
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Abstract
A method for detecting unstable signatures when testing a VLSI chip that includes adding to an LFSR one or more save and restore registers for storing an initial seed consisting of 0s and 1s; loading the initial seed into the one or more save and restoring LFSR registers upon reaching a predetermined number of test loops; performing a signature stability test by loading said initial seed to said LFSR, executing the predetermined number of BIST test loops, and comparing the resulting MISR signature for differences versus a previous signature stored in a MISR save and restore register.
Claims20
A method for detecting unstable signatures when testing a VLSI chip comprising:
- a) adding to a linear feedback shift register (LFSR) one or more save and restore registers for storing an initial seed consisting of 0s and 1s;
- b) loading said initial seed into said one or more save and restore registers upon reaching a predetermined number of test loops;
- and
- c) performing a signature stability test by loading said initial seed to said LFSR, executing said predetermined number of BIST test loops, and comparing a resulting MISR signature for differences versus a previous signature stored in a MISR save and restore register.
Dependencies are inferred from the claim text.