TEST RESPONSE COMPACTION USING MULTIPLEXED PARITY TREES

Built-in self-testing requires test response streams from many observa tion points to be merged (space compaction) and compressed (time compa ction) into a short signature, The compaction circuits should be trans parent to error propagation in order to minimize aliasing, which occur s when a faulty response maps to the fault-free signature, We investig ate the use of multiplexed parity trees (MPT's) for zero-aliasing spac e compaction. MPT's combine the error propagation properties of multip lexers and parity trees, and ensure zero aliasing via multistep compac tion, We present two design techniques based on MPTs-output selection and fanout insertion-that eliminate aliasing for both deterministic an d pseudorandom test sets, Our experiments with the ISCAS benchmark cir cuits show that zero aliasing can be achieved with small test sets and moderate hardware overhead. We also demonstrate that a very high perc entage of single stuck-line faults in the compaction circuit are detec ted by the test patterns applied to the circuit under test.