SCAN/BIST Techniques for Decreasing Test Storage and their implications to Test Pattern Generation

Test pattern storage is an important problem aaect-ing all Design for Testability (DfT) techniques based on scan-path. Built-In Self Test (BIST) methodologies are used in conjunction to scan-path techniques for reducing the amount of test patterns that must be stored. This paper analyzes two SCAN/BIST approaches and identiies conditions which guarantee that such techniques require shorter test sequences in relation to a simple scan method. Such conditions concern the ability of sequential test pattern generators (TPGs) to con-catenate test sequences, but, unfortunately, standard sequential TPGs do not show suucient capabilities in this task. Thus, the paper presents an innovative con-catenation strategy for test sequences based on implicit techniques. Preliminary results and a case-study show that the use of the presented SCAN/BIST approaches, with the proposed test generation strategy, generates a test methodology that sensibly reduce the amount of test patterns which must be stored.