Hybrid test data compression technique for SOC scan testing

A hybrid test data compression technique is proposed to reduce the test application time while keeping test power low by assigning "don\´t cares" to reduce transitions. Initially, test data set is compressed by 0/1 prefix run-length codes. Then, the compressed data are chopped into fixed-length blocks and further encoded by Huffman algorithm. It is observed that the global compression is highly dependent upon the chopping size of initially compressed data upon run-length codes. Since the actual Huffman codes make use of a very small portion of the complete coding space, the decoding logic of our hybrid scheme can be implemented with a very small area penalty. The experiments show significant data compression compared with state-of-the-art techniques