A loop-based apparatus for at-speed self-testing
At-speed testing using external tester requires an expensive equip ment, thus built-in self-test (BIST) is an alternative technique due to its ability to perform on-chip at-speed self-testing. The main issue in BIST for at-speed testing is to obtain high delay fault coverage with a low hardware overhead. This paper presents an improved loop-based BIST scheme, in which a configurable MISR (multiple-input signature register) is used to generate test-pair sequences. The structure and operation modes of the BIST scheme are described. The topological properties of the state-transition-graph of the proposed BIST scheme are analyzed. Based on it, an approach to design and efficiently implement the proposed BIST scheme is developed. Experimental results on academic benchmark circuits are presented to demonstrate the effectiveness of the proposed BIST scheme as well as the design approach.
at-speed test built-in self-test multiple input shift register state transition graph