A Rollback Interval for Networks with an Imperfect Self-Checking Property

Abstract

Dynamic self-checking is a technique used in computers to detect a fault quickly before extensive data contamination caused by the fault can occur. When the self-checking properties of the computer circuits are not perfect, as in the case of self-testing only and partially self-checking circuits, a recovery procedure may be required to roll back program execution to a point prior to the first undetected data error caused by the detected fault. This paper presents a method by which the rollback distance required to achieve a given probability of successful data restoration may be calculated. To facilitate this method, operational interpretations are given to familiar network properties such as the self-testing, secureness, and self-checking properties. This paper assumes the use of dynamically checked combinational networks between latches in a synchronous design. Consideration is therefore limited to combinational networks. An arithmetic and logic unit with imperfect self-checking capability is analyzed to determine the minimum required rollback distance for the recovery procedure. Copyright © 1978 by The Institute of Electrical and Electronics Engineers. Inc.