A DIAGNOSIS ALGORITHM FOR CONSTANT DEGREE STRUCTURES AND ITS APPLICATION TO VLSI CIRCUIT TESTING

A simple diagnosis algorithm is presented for constant degree systems such as rectangular grids connected as tori, The algorithm determines the status of a unit according to the size of its faction, a cluster of units that call each other fault-free but outsiders faulty, Almost all units are correctly identified with this algorithm under a binomial failure distribution even when the probability of failure is rather high, The complexity of the algorithm is O(n), where n is the number of units in a constant degree system, The application of the algorithm to production testing of VLSI chips is also considered, With a test board that houses a large number of chips to be tested, all the chips can be tested in parallel in a way that they test each other and the test outcomes, not necessarily correct, are reported to a host system for analysis. The actual status of each chip is determined by using this new diagnosis algorithm, The above chip screening process can be repeated for higher accuracy, It is shown that no more than two steps are needed in most real situations, Compared with testing by test equipment that usually tests only one chip at a time, the saving of test time and the test equipment cost could be significant with our approach.