A Same/Different Fault Dictionary: An Extended Pass/Fail Fault Dictionary with Improved Diagnostic Resolution

We describe a new type of fault dictionary called a same/different fault dictionary. 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 modeled 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; while 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 to a pass/fail fault dictionary. We describe a procedure for selecting baseline output vectors and present experimental results.