Sequential test generation and synthesis for testability at the register-transfer and logic levels

The problem of test generation for nonscan sequential VLSI circuits is addressed. A novel method of test generation that efficiently generates test sequences for stuck-at faults in the logic circuit by exploiting register-transfer-level (RTL) design information is presented. The approach is targeted at circuits with highly connected state transition graphs (STGs) as in data paths, but explicit use is not made of the STG. The efficacy of the method stems from the use of the RTL description and good heuristics. The authors have successfully generated tests for entire chips with large numbers of latches within reasonable amounts of CPU time and have obtained maximum fault coverage. The algorithms require significantly smaller times than other test generators. A synthesis procedure that produces an optimized, fully testable logic implementation of a sequential circuit from a RTL description of the sequential circuit is also described. Datapath-controller circuits as well as digital signal processors whose STGs are very large, can be synthesized. The problem of synthesis of sequential logic for testability is also addressed.>