A METHOD OF DIAGNOSING BRIDGING FAULTS BETWEEN N-NETS IN COMBINATIONAL-CIRCUITS

The observation of signal values inside a circuit by probing is very effective in diagnosing faults. However, since probing requires considerable effort, it is designed to decrease the number of locations to be probed as much as possible. For multiple stuck-at-faults, a method which enables efficient diagnosis by jointly using deductions and probing has been proposed. This paper shows that the basic operations of this method are applicable to the diagnosis of single bridging faults between n(greater than or equal to 2) nets, which function as wired AND (OR). In the authors' diagnostic method, in addition to these basic operations, to improve diagnostic efficiency the selection method of locations to be probed is improved and the concept of forced value used for deducing signal values inside the circuit is extended. The results of computer experiments show that the diagnostic time is proportional to the product of the number of lines and the number of tests, and that by probing about 10-20 percent of all lines, fault locations can be indicated with fairly high accuracy.