Identifying sequentially untestable faults using illegal states

Identifying sequential redundancies without search

“…Among the seven c-cycle redundant faults identified by FIRES in the above example, FUNTEST [19] will report only one (g 0 ) as untestable, and FUNI [20] will identify two (g 0 and f 0 ) as untestable by processing the illegal state {g, h} = {1, 0}. The example also shows that FIRES can find faults that are beyond the scope of the combinational ATG theorems [8] [9] ( f 0 , e 1 , d 0 , d 1 , a 0 , and b 0 ).…”

“…However, the use of the single-fault theorem to identify sequentially untestable faults precludes identifying redundancy [10] . The FUNI algorithm [20] Finds UNtestable faults without search using Illegal states. FUNI cannot distinguish between untestable and redundant faults.…”

Sequential redundancy identification using recursive learning

“…Because the conditions for S x , S y and S z cannot be satisfied simultaneously, faults in S xyz = S x T S y T S z are redundant. The faults that belong to S x can be found by uncontrollability and unobservability analysis [1,2,3]. Let 0(1) denote the status of a line that is uncontrollable to value 0(1).…”

“…In [8], it is proven that a fault identified by FIRES is c-cycle redundant. In [3], FUNI, a sequential untestable identification algorithm, was proposed. FUNI is composed of two steps.…”

“…Most previous methods for identifying sequentially redundant and untestable faults [4] [5] [6] are based on ATPG, requiring large amounts of computations. Recently, two fault-independent sequential redundant and untestable fault identification algorithms, FIRES [13] and FUNI [3], have been proposed. Based on uncontrollability and unobservability analysis, FIRES finds redundant faults This work is supported in part by NSF under Grant MIP 94-06946 and byONR under Grant N00014-92- 1-1366. whose activation or observation requires conflicting assignments on fanout stems.…”