A comprehensive approach to the partial scan problem using implicit state enumeration

This paper presents a novel technique and a practical algorithm for the selection of state registers for partial scan. Our model uses implicit techniques for FSM traversal to identify non-controllable state registers. Non-controllability of registers is evaluated by a systematic analysis of the state transitions and the encoding of the underlying FSM. By using our approach, we can not only identify non-controllable and difficult-to-control flip-flops, but also exploit the information of the unreachable states to judiciously select the minimum number of scan registers for high fault coverage. The effectiveness of our technique is illustrated over a large set of MCNC and ISCAS benchmarks. The results demonstrate the superiority of our method over conventional state-of-the-art scan register selection techniques in terms of higher fault coverage achieved by selecting fewer partial scan registers.