Optimal frequencies for concurrent and periodical tests of logical systems

Testing and maintenance periodically executed have been often associated in the past. But the parameters on which these phenomena are acting are not always identical. A first part of this paper is thus concerned with the differentiation of these parameters. Periodical testing phenomena are then entered upon in view of concurrent testing. These concurrent tests are using both failure detectors, that are inherent to the system and dependent on a periodical phenomenon, and periodically executed tests. These results have been obtained for concurrent testing of CPUs (especially microprocessors) although they are useful for simpler applications such as periodical testing of components belonging to a board or generally of sub-systems belonging to a global system