AUTOMATIC FAULT-DIAGNOSIS FOR SCAN-BASED DESIGNS

This contribution presents an automatic fault diagnosis system which i s designed to combinational circuits and circuit modules embedded in a scan path environment. It consists of a diagnosis software called DIA BOLO (DIAgnosis of BOolean LOgic), an electron beam tester (EBT) and a digital tester. A novel concept for a complete automatic fault diagno sis process is proposed: The applied test patterns and test sequences are specifically generated for the fault diagnosis of scan-based circu its with support of the EBT. This approach allows the drastic reductio n of EBT measurement times respectively the reduction of the number of internal circuit nodes which have to be observed by the EBT. Each ste p of the fault diagnosis process has certain requirements for the appl ied test patterns and test sequences. Therefore, different types of te st patterns and sequences are applied during one diagnosis run, for ex ample, inherently periodical test patterns [1], diagnostic test patter ns [2] and short test sequences are employed [3]. The test pattern / s equence generation is performed automatically (which is the prerequisi te for automatic fault diagnosis) and online, that is it depends on th e predecessing results of the actual fault diagnosis process. Experime nts demonstrate the feasibility of the proposed concept.