TESTING FOR SINGLE FAULTS IN MODULAR COMBINATIONAL NETWORKS.

Fault detection in digital systems has long been recognized as an important problem, and numerous papers deal with this aspect in combinational networks composed of logic gates. On the other hand, there has not been much attention given to developing fault detection test patterns for modular combinational networks widely associated with modern techniques. This paper proposes an algorithm for detecting all single faults in modular combinational networks. Each module is characterized by its Boolean function. Firstly, only pin-stuck-faults are considered, namely, the modules are assumed to be reliable and the faults expected only in the intermodular lines and inputs and output. It is shown that a set of tests detecting all single faults at the inputs of a tree-structured modular combinational network does not necessarily detect all single pin faults within the network. Later, the algorithm is extended to cover all possible single stuck-at-type faults, whether internal or external to the modules. The algorithm makes use of the Boolean difference technique.