Research On Don't Care Inputs Identifier And Test Generation Algorithm Based On Chaotic Search

With the continuous development of IC (Integrated Circuit) testing technology, IDDT testing, which is a complement of traditional voltage testing and IDDQ testing,gains more and more attention from research and industry field.The test generation of IDDT testing needs several test vectors at one time(two or more) . The relevant ATPG (Automatic Test Pattern Generation) algorithm is complex and the time consumption is also very large.Therefore, it is of great significance to find effective ATPG algorithms.Firstly, the history and theory of digital circuit testing is introduced. And the existing ATPG algorithms are summed up.Secondly, directing at detecting stuck-open fault of the circuit, an IDDT test generation algorithm based on chaotic search is proposed.The algorithm takes sufficient consideration of the topology of CUT (Circuit Under Test), uses backward implication in FAN algorithm to activate fault and adopts chaotic search to find out suitable testing pairs.It can assure certain fault coverage while effectively decrease test generation time.SPICE simulation results show the algorithm is effective.Consequently, directing at the problem that the search space of IDDT test generation algorithm is too large, a circuit dividing strategy is proposed.By analyzing the process of fault propagation, three kinds of circuit nodes which affect fault propagation are detected.Thus, primary inputs controlling these nodes are also be detected.therefore, by eliminating the primary inputs which make no contribution to fault propagation, a smaller search space is obtained.Finally, a method for identifying don't care inputs is presented.Given a test set for stuck-at faults, some of primary input values may be changed to opposite logic values without losing fault coverage.Such input values are regared as don't care(X).The proposed method finds the test set contains X inputs as many as possible,by analyzing fault propagation path and procedures similar to implication and justification of ATPG algorithms.The experimental result show approximately 26% of primary inputs can be X.The proposed method can be applicated to test compaction and reduction of power dissipation during testing and can achieve good effect.