On Minimally Testable Logic Networks

A new technique to modify any logic network to facilitate diagnosis is given. By providing extra controllable inputs (at most six) and observable outputs it is shown that any number of stuck-at-faults in a logic network can be detected by applying only three tests. This number is believed to be minimal for networks using current technologies. Example of logic module that can be used to realize any logic function such that only two tests detect stuck-at-faults is also given.