On-chip logic to log failures during production testing and enable debugging for failure diagnosis

摘要

On-chip logic includes a shadow register cross-coupled with a multiple input shift/signature register (MISR). The shadow register facilitates debugging by shifting out a test signature while resetting the MISR with a fault-free signature. The on-chip logic may further include comparator circuitry to produce an output signal by comparing the test signature with the fault-free signature or by first compressing the test signature and then comparing the compressed test signature with the compressed fault-free signature.