On the design of self-checking systems under various fault-models

Codes that are used to protect against unidirectional errors were studied. Systematic and non-systematic codes were shown to have the same basic structure. The structure of non-systematic unordered codes, more precisely the class of fixed-weight codes was further examined. It was shown that these codes have codewords that can be effectively classified in terms of congruence, cycling and complementation classes. The capabilities of unordered codes were defined with respect to circuit structure and fault models. Some results, based on the previous classification scheme, are presented on the design of two level minimal checkers. Some practical suggestions for and limitations on the use of unordered codes under different fault models are described.