Analysis of Two Pattern Test Cubes for Transition Path Delay Faults in Digital Circuits

A method is presented for identifying primitive path-delay faults in non-scan sequential circuits and generating robust tests for all robustly testable primitive faults. It uses the concept of sensitizing cubes introduced in an earlier paper and a new, more efficient algorithm for generating them. Sensitizing cubes of the next state and output logic are used to obtain static sensitizing vectors that can be applied to the non-scan sequential circuit as part of a vector-pair. These vector-pairs are also used in deriving robust tests. Initializing sequences from a reset state and sequences that propagate fault effects from flip-flops to primary outputs are also generated. The proposed procedure unspecified them gradually to obtain a series of test sets with increasing numbers of unspecified values and decreasing path lengths. Experimental results also indicate that filling the unspecified values randomly (as with some test data compression methods) recovers some or all of the path lengths associated with detected path delay faults. The procedure uses a matching of the sets of detected faults for the comparison of path lengths. Keywords—Full-scan circuits, path delay faults, test cubes, transition faults, twopattern tests.