Restoration-Based Merging of Functional Test Sequences

Abstract

This paper develops a merging procedure for functional test sequences that achieves test compaction for a pool of functional test sequences by reducing the number of sequences in the pool. The procedure has the following new features: 1) in contrast to existing selection procedures, the merging procedure described in this paper increases the fault coverage of test sequences in the pool, thus enhancing the ability to reduce the number of sequences and 2) in contrast to existing procedures that concatenate or merge test sequences, the procedure described in this paper does not increase the lengths of the sequences it merges. The procedure is based on the concept of restoration of test vectors. In the context of test sequence merging, restoration consists of copying test vectors from a test sequence $ {T_{j}}$ into a test sequence $ {T_{i}}$ in order to allow $ {T_{i}}$ to detect faults that $ {T_{j}}$ detects. The merging procedure focuses on the removal of one test sequence $ {T_{j}}$ at a time by restoring test vectors from $ {T_{j}}$ into other sequences, allowing them to detect the faults that $ {T_{j}}$ detects. Experimental results for benchmark circuits demonstrate that the procedure reduces the number of sequences in a pool significantly.