Concatenation of Functional Test Subsequences for Improved Fault Coverage and Reduced Test Length

Functional test sequences have several advantages over structural tests when they are applied at-speed. A large pool of functional test sequences may be available for a circuit due to the application of a simulation-based design verification process. This paper describes a versatile procedure that uses a pool of functional test sequences as a basis for forming a single compact functional test sequence that achieves the same or higher gate-level fault coverage than the given pool. The procedure extracts test subsequences from the test sequences in the pool and concatenates them to form a single test sequence. It also employs an enhanced static test compaction process aimed at improving the fault coverage in addition to reducing the test sequence length.