COMPAS — Advanced test compressor

This paper describes the compression method that is used for test pattern compaction and compression in algorithm called COMPAS, which utilizes a test data compression method based on pattern overlapping. This algorithm reorders and compresses deterministic test patterns previously generated in an ATPG by overlapping them. COMPAS is able to use distributed ATPG processing and compress test data for various fault models. Independency of COMPAS on used ATPG is discussed and verified. The compressor preprocesses the input data to determine the degree of random test resistance for each fault. This allows to reorder the test patterns more efficiently and results to 10% compression ratio improvement in average. Compressed data sequence is well suited for decompression by the scan chains in the embedded tester cores.