Timed Discrete event system approach to online testing of asynchronous circuits

Now-a-days On-line testing becomes an indispensable part of DFT (design for testability) for detecting rapidly increasing intermittent faults in deep sub-micron ICs. Much of the proposed on-line testing techniques are for synchronous circuits as compared to asynchronous circuits. The existing online testing(OLT) techniques of asynchronous circuits involve development of checkers that verify the correctness of the predefined protocol. The area overhead of this type of checkers is quit high because of Mutex blocks, which are the main component of the checker. In this paper, we have adapted the theory of Failure Detection and Diagnosis(FDD) available in the literature on Timed Discrete Event Systems(TDES) to on-line testing of asynchronous circuits. The proposed scheme includes modeling the behavior of the circuit under normal and various stuck at fault conditions and eventually, an on-chip detector circuit is designed. The detector monitors the circuit on-line and determines whether the circuit is functioning in normal or failure mode. The main advantages of this scheme are non-intrusiveness and low area overheads compared to similar schemes reported in the literature.