Efficient implementations of self-checking adders and ALUs

Abstract

The author presents efficient self-checking implementations for adders and ALUs (ripple carry, carry lookahead, carry skip schemes). Among all the known self-checking adders and ALUs the parity prediction scheme has the advantage to require the minimum overhead for the adder/ALU and the minimum overhead for the other data path blocks. It has also the advantage to be compatible with memory systems checked by parity codes. The drawback of this scheme is that it is not fault secure even for single stuck-at faults. The new designs require lower overhead than the above scheme and also they have all the other advantages of this scheme. In addition the new schemes are strongly fault secure or totally self-checking for a comprehensive fault model which includes stuck-at, stuck-on and stuck open faults. Thus, the new schemes are substantially better than any other known scheme.