On Generating Fault Diagnosis Patterns for Designs with X Sources
Xijiang Lin, Sudhakar M. Reddy · 2019
Fault diagnosis patterns distinguish pairs of faults and are used to improve fault diagnosis resolution. Earlier, several methods to generate fault diagnosis patterns have been proposed. We demonstrate that all but one earlier proposed methods may generate invalid patterns when the circuit under test (CUT) has X sources, which is typically true for industrial designs. The earlier proposed method that can generate valid diagnosis patterns in the presence of X sources uses two copies of the CUT to generate diagnosis tests, thus requiring larger memory and run time. In addition, to use ATPGs that generate test to detect single fault, earlier methods require circuit modification for each pair of faults to be distinguished, requiring multiple loadings of the CUT, thus increasing run times. We propose a method to generate valid diagnosis patterns using a single copy of the CUT and using a standard single fault detection ATPG with minor modification. The proposed method does not require modifying the circuit to generate diagnosis patterns. Experimental results are presented to demonstrate the effectiveness of the proposed method.