Same/different fault dictionary: an extended pass/fail fault dictionary with improved diagnostic resolution

A new type of fault dictionary called a same/different fault dictionary is described. The same/different fault dictionary is similar to a pass/fail fault dictionary in that it contains a single bit b _i,j for every modelled fault f _i and test vector t _j. However, in a pass/fail fault dictionary, b _i,j is determined by comparing the output vector of the faulty circuit with the output vector of the fault-free circuit; whereas in a same/different fault dictionary, b _i,j is determined by comparing the output vector of the faulty circuit with a preselected output vector called a baseline output vector. By selecting appropriately the baseline output vectors for all the test vectors, it is possible to obtain increased diagnostic resolution with a same/different fault dictionary compared with a pass/fail fault dictionary. A heuristic procedure for selecting baseline output vectors is described and experimental results are presented.