Techniques for Self-Checking Combinational Logic Synthesis

Abstract

This paper presents techniques for designing arbitrary combinational circuits so that any single stuck-at fault will result in either single bit error or unidirectional multibit error at the output. If the outputs are encoded using Berger code or m-out-of-n code, then the proposed technique will enable on-line detection of faults in the circuit. An algorithm for indicating whether a certain fault at an input will create bidirectional error at the output is presented. An input encoding algorithm and an output encoding algorithm that ensure that every fault will either produce single bit error or unidirectional multibit error at the output are proposed. If there are no input fault which produces bidirectional error, no internal stuck-at fault will result in such an error irrespective of the way the circuit is implemented. Thus, only single bit or unidirectional multibit error will result in the presence of a fault in the circuit. The proposed techniques have been applied to MCNC benchmark circuits and the overhead is estimated.