Abstract: A new test data compression based on logical operation and dimidiate partition was proposed. The whole test was partitioned to several length-fixed blocks. Then logical operation was applied into runs of Is or 0s or alternating bits. They were turned into all 0s. For the others, dimidiate partition technique was used until they got to the minimum length. The length of code words could be expressed by the times of dimidiate and it is easy to coding when they are turned into all 0s. Compared with traditional data-coding methods the depression structure is simple and reduced the costs of decompression.

Key words: test data compression, logical operation, dimidiate partition, alternating bits