Fault diagnosis assistant (VLSI chips)

A description is given of a first implementation of a knowledge-based system for interactive support of test engineers in gate-level troubleshooting of faulty VLSI chips. The fault diagnosis assistant (FDA) offers advice on the next-best internal probe point for an electron-beam test probe system. The current OPS83 production system implementation of FDA recommends an efficient sequence of probes at internal nodes that progressively localizes and identified single stuck-at faults in combinational logic or combinational partitions within set/scan logic. Its model-based diagnostic methodology is based primarily on using model knowledge of the system´s structure (connectivity file) and function (normal, design-prescribed behavior) of the system´s primitive components. Some FDA implementation details and pattern-matching efficiency considerations, initial FDA timing experiments, and future extensions to FDA are considered.<>