Fully testable PLA design with minimal extra input

Due to its popular application in the design of LSI/VLSI circuits, testable PLAs have become an important topic. Bozorgui-Nesbat and McCluskey (1986) offered a low-overhead method which adds extra inputs rather than shift registers to design a fully testable PLA. However, to design such a PLA with a minimal number of extra inputs is an NP complete problem. A rule to modify an arbitrary irredundant PLA which needs fewer extra inputs than other existing methods to make the modified PLA fully testable is presented. It covers multiple stuck-at faults, multiple extra devices, and multiple missing devices, except multiple redundant extra devices in the OR plane of a PLA. In addition, the aforementioned problem is shown no longer NP complete for the modified PLA