TEST DATA COMPRESSION USING NINE CODED RUN LENGTH BASED HUFFMAN CODING

Abstract: In this paper, we present an compression technique to reduce the test patter volume in scan test applications. We have proposed an encoding scheme which is run-length based Huffman coding (RLHC). This encoding scheme together with the nine-coded compression technique enhances the test data compression ratio. In the first step, the pre-generated test data with unspecified bits are encoded using the nine-coded compression technique then the run-length based Huffman code is applied to the encoded data. This compression technique is very effective when the percentage of do not cares in a test set is high. We also present the simple decoder architecture to decode the original data. Experimental results on ISCAS’89 benchmark circuits show the effectiveness of the proposed method compared with other test-independent compression techniques.

Keywords: Test data compression, Nine-coded compression, Huffman coding, Design for testability, VLSI testing.