Design for easily applying test vectors to improve delay fault coverage

It has been noted that arbitrary test pairs ( nu /sub 1/, nu /sub 2/) cannot be applied to a combinational pair of a finite state machine using standard scan path design. The scan path design is a special case of test machines which are designed to control and observe the object machine for detecting faults. By studying state transition graphs, the authors propose a general framework, which is composed of two stages, to solve this problem. Given a set of test pairs and a set of test machines, the first stage is to select a test machine which has the maximum delay fault coverage. If the fault coverage is not satisfactory, two approaches are proposed at the second stage. It is shown that these two optimization problems in the second stage are both NP-hard. Three algorithms are designed to solve these problems.<>