Browse Reports

The structure of a circuit determines how the effects of a fault can propagate and hence affects the cost of concurrent error detection. By considering circuit structure during logic optimization, the overall cost of a concurrently checked circuit can be minimized. This report presents a new technique called structure-constrained logic optimization (SCLO) that optimizes a circuit under the constraint that faults in the resulting circuit can produce only a prescribed set of errors. Using SCLO, circuits can be optimized for various concurrent error detection schemes allowing the overall cost for each scheme to be compared. A technique for quickly estimating the size of a circuit under different structural constraints is described. This technique enables rapid exploration of the design space for concurrently checked circuits. A new method for the automated synthesis of self-checking circuit implementations for arbitrary combinational circuits is also presented. It consists of an algorithm that determines the best parity-check code for encoding the output of a given circuit, and then uses SCLO to produce the functional circuit which is augmented with a checker to form a self-checking circuit. This synthesis method provides fully automated design, explores a larger design space than other methods, and uses simple checkers. It has been implemented by making modifications to SIS (an updated version of MIS [Brayton 87a]), and results for several MCNC combinational benchmark circuits are given. In most cases, a substantial reduction in overhead compared to a duplicate-and-compare implementation is achieved.