A Huffman-based coding with efficient test application

Test compression/decompression method using variable-length coding is an efficient method for reducing the test application cost, i.e., test application time and the size of the storage of an LSI tester. However, some coding imposes slow test application, and consequently it requires large test application time in spite of its high compression. In this paper, we clarify the fact that test application time depends on the compression ratio and the length of codewords, and then propose a new Huffman-based coding method for achieving small test application time in a given test environment. The proposed coding method adjusts both of the compression ratio and the length of the cord words to the test environment. Experimental results show that the proposed method can achieve small test application time while keeping high compression ratio.