UMC-Scan Test Methodology: Exploiting the Maximum Freedom of Multicasting

Industry has used scan-based designs widely to promote test quality. However, for larger designs, the growing test data volume has significantly increased test cost because of excessively long test times and elevated tester memory and external test channel requirements. To address these problems, researchers have proposed numerous test compression architectures. In this article, we propose a flexible scan test methodology called universal multicasting scan (UMC scan). It has three major features: First, it provides a better than state-of-the-art test compression ratio using multicasting. Second, it accepts any existing test patterns and doesn't need ATPG support. Third, unlike most previous multicasting schemes that use mapping logic to partition the scan chains into hard configurations, UMC scan's compatible scan chain groups are defined by control bits, as in the segmented addressable scan (SAS) architecture. We have developed several techniques to reduce the extra control bits so that the overall test compression ratio can approach that of the ideal multicasting scheme.