A Functional Decomposition Method for Redundancy Identification and Test Generation

We present a new combinational circuit automatic test-pattern generation (ATPG)acceleration method called EST that detects equivalent search states, which are saved for later use. The search space is learned and characterized using E-frontiers, which are circuit cut-sets induced by theimplication stack contents. The search space is reduced by matchingthe current search state against previously-encountered search states(possibly from prior faults), and this reduces the length of thesearch. A second contribution is a calculus of redundant faults, which enables EST to make many more mandatoryassignments before search than is possible by prior algorithms, byeffectively using its knowledge of prior faults proven to beredundant. This accelerates ATPG for subsequent faults. Thesemethods accelerate the TOPS algorithm 33.3 times for thehard-to-test faults in the ISCAS 85 benchmarks, and the SOCRATES algorithm 5.6 times for the same hard-to-test faults, with little memory overhead.