Efficient Test-Data Compression for IP Cores Using Multilevel Huffman Coding

In this paper we introduce a new test-data compression method for IP cores with unknown structure. The proposed method encodes the test data provided by the core vendor using a new, very effective compression scheme based on multilevel Huffman coding. Specifically, three different kinds of information are compressed using the same Huffman code, and thus significant test data reductions are achieved. A simple architecture is proposed for decoding on-chip the compressed data. Its hardware overhead is very low and comparable to that of the most efficient methods in the literature. Additionally, the proposed technique offers increased probability of detection of unmodeled faults since the majority of the unknown values of the test set are replaced by pseudorandom data generated by an LFSR.