Reduced-size Signature-based Diagnostic Dictionary for Interconnection Testing

The paper deals with a new and advanced method intended to reduce size of a diagnostic dictionary that is used for detection, localization and identification of static and delay faults in interconnections that are tested with use of ring linear feedback shift registers (R-LFSR). The proposed method assumes that the bus under test comprises n lines and is structured into b fragments with the size of k lines per each fragment. The method also assumes that each of the aforementioned fragments is tested by means of a separate R-LFSR with its length of 2k bits. In addition, the paper proposes to subdivide the test procedure into four phases whereas odd and even R-LFSRs are activated alternately. It is the way of subdivision that makes it possible to get rid of the mutual interference between two adjacent R-LFSRs when a short between feedback lines of these neighbouring registers takes place. Likelihood of such interactions was the drawback of previous methods and presented the impediment that prevented the fault dictionary from having its size reduced. The innovative solution that is suggested in this study enables to substantially diminish the dictionary, where its actual size is determined by the multiplicity of r defects within each k-bit part of the connecting bus, even when the bus width n >> k.