Automatic fault diagnosis for scan-based designs

This contribution presents an automatic fault diagnosis system which is designed to combinational circuits and circuit modules embedded in a scan path environment. It consists of a diagnosis software called DIABOLO (DIAgnosis of BOolean LOgic), an electron beam tester (EBT) and a digital tester. A novel concept for a complete automatic fault diagnosis process is proposed: The applied test patterns and test sequences are specifically generated for the fault diagnosis of scan-based circuits with support of the EBT. This approach allows the drastic reduction of EBT measurement times respectively the reduction of the number of internal circuit nodes which have to be observed by the EBT. Each step of the fault diagnosis process has certain requirements for the applied test patterns and test sequences. Therefore, different types of test patterns and sequences are applied during one diagnosis run, for example, inherently periodical test patterns [1], diagnostic test patterns [2] and short test sequences are employed [3]. The test pattern / sequence generation is performed automatically (which is the prerequisite for automatic fault diagnosis) and online, that is it depends on the predecessing results of the actual fault diagnosis process. Experiments demonstrate the feasibility of the proposed concept.