Test generation is one of the most difficult tasks facing the designer of complex VLSI-based digital systems. Much of this difficulty is attributable to the almost universal use in testing of low, gate-level circuit and fault models that predate integrated circuit technology. It is long been recognized that the testing prob­ lem can be alleviated by the use of higher-level methods in which multigate modules or cells are the primitive components in test generation; however, the development of such methods has proceeded very slowly. To be acceptable, high-level approaches should be applicable to most types of digital circuits, and should provide fault coverage comparable to that of traditional, low-level methods. The fault coverage problem has, perhaps, been the most intractable, due to continued reliance in the testing industry on the single stuck-line (SSL) fault model, which is tightly bound to the gate level of abstraction. This monograph presents a novel approach to solving the foregoing problem. It is based on the systematic use of multibit vectors rather than single bits to represent logic signals, including fault signals. A circuit is viewed as a collection of high-level components such as adders, multiplexers, and registers, interconnected by n-bit buses. To match this high-level circuit model, we introduce a high-level bus fault that, in effect, replaces a large number of SSL faults and allows them to be tested in parallel. However, by reducing the bus size from n to one, we can obtain the traditional gate-level circuit and models.

Inhalt

1 Introduction.- 1.1 Background.- 1.2 Prior Work.- 1.2.1 Test Generation for Combinational Circuits.- 1.2.2 Test Generation for Sequential Circuits.- 1.2.3 High-level Test Generation.- 1.2.4 Fault Simulation.- 1.2.5 Design for Testability.- 1.3 Outline.- 2 Circuit and Fault Modeling.- 2.1 Vector Sequence Notation.- 2.2 Circuit and Fault Models.- 2.2.1 Circuit Model.- 2.2.2 Fault Model.- 2.3 Case Study: k-Regular Circuits.- 3 Hierarchical Test Generation.- 3.1 Vector Cubes.- 3.2 Test Generation.- 3.2.1 Repetitive Circuits.- 3.2.2 Pseudo-Sequential Circuits.- 3.2.3 High-Level Test Generation Algorithm.- 3.3 Implementation and Experimental Results.- 3.3.1 Circuit Description.- 3.3.2 Data Structures.- 3.3.3 Program Structure.- 3.3.4 Experimental Results.- 4 Design for Testability.- 4.1 Ad Hoc Techniques.- 4.1.1 Array-Like Circuits.- 4.1.2 Tree-Like Circuits.- 4.2 Level Separation (LS) Method.- 4.2.1 Functions Realizable by One-Dimensional ILA's.- 4.2.2 Functions Realizable by Two-Dimensional ILA's.- 4.3 Case Study: ALU.- 5 Concluding Remarks.- 5.1 Summary.- 5.2 Future Directions.- Appendix A: Proofs of Theorems.- A.1 Proof of Theorem 3.2.- A.2 Proof of Theorem 3.3.- A.3 Proof of Theorem 4.1.