Anomalous effect of a stuck-at fault in a combinational logic circuit

An example of an irredundant combinational network realizing a Boolean function F0is presented which depicts a peculiar phenomenon that even a single stuck-at fault can change the function F0to a faulty funetion Ff, such that F0and Ffbelong to the same P-equivalence class, i.e., F0can be transformed into Ffby permuting the input literals. In addition, the reversibility of fault behavior in irredundant networks is also exemplified.