Reduced scan shift: a new testing method for sequential circuits

Abstract

This paper presents a new testing method for sequential circuits, called reduced scan shift, which generates short test sequences. In this method, only part of flip-flops close to the scan input line are controlled and another part of flip-flops close to the scan output line are observed by scan shift operations as small as possible. For the purpose of reducing scan shift operations, the following points are considered: (1) how to decide target faults which each test vector should detects, (2) how to arrange flip-flops in the scan chain, (3) how to decide the order of test vectors. Experimental results for ISCAS'89 benchmark circuits are given to show the effectiveness of this method.