SIGNATURE COMPRESSION REGISTER INSTABILITY ISOLATION AND STABLE SIGNATURE MASK GENERATION FOR TESTING VLSI CHIPS

摘要

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.