Self-checking combinational circuit design for single and unidirectional multibit error

This article presents novel input and output encoding techniques such that the resulting circuit is bidirectional error-free. The circuit can be fully optimized and any types of gates can be used. These schemes are used to design the functional part of a self-checking circuit. The input encoding algorithm can be applied to any circuit without significantly increasing the input lines. The output encoding technique involves graph-embedding which is done with heuristic method of polynomial complexity. The heuristic technique produces nearly optimal output encoding. Previously published work restrict the types of gates used in the circuit to non-inversion gates (AND/OR), and use inverters only at the inputs. The proposed techniques have a clear advantage over the currently available techniques because they allow the use of any types of gates. These techniques do not necessarily increase the overhead when applied to different MCNC benchmark circuits as the experimental results indicate. The only restriction is that either the inputs or the outputs have to be symbolic, and the two-level description of a circuit has to be given.