Isomorph-redundancy in sequential circuits

An isomorph fault in a sequential circuit makes the state diagram of the faulty machine identical to that of the fault-free machine, under the renaming of states. However, no example of a reduced sequential machine whose circuit realization is combinationally irredundant but isomorph-redundant, is yet known. This paper shows that an infinite family of such circuits can be constructed with isomorph-redundancy. Isomorph faults are then classified into various types. Their properties reveal new insight and understanding of redundancy in sequential circuits.