采用循环移位和优化编码的测试压缩方法

日益增加的集成电路测试成本变得越来越难以接受,因而提出了一种简单而有效的解决方案.该方案把循环移位技术应用到测试数据压缩中,比起一般的移位技术,该方案更能有效地利用测试集中无关位.结合异或逻辑运算,所提方案累积无关位,进一步提高测试向量与其参考向量的相容性和反向相容性.在编码过程中对各种可能移位状态进行统计,建立Huffman树,找出最优化编码形式,因而可以增加短码字的利用率,减少长码字的使用频次.通过给出的分析和实验,说明了所提方案在附加硬件成本很低的情况下既能够提高测试数据压缩率,又能够减少测试时间,优于已发表的游程编码方案和其他同类型的编码压缩技术.

Test Compression Approach of Adopting Cyclic Shift and Optimal Coding

It is more difficult to accept the increasing test cost for ICs,and hence a simple and high effective solution scheme is proposed in this paper.Cyclic shift technique is applied to test data compression,which can make use of don’t bits in test set more effectively than general shift techniques.Combining with XOR logic,the proposed scheme cumulates don’t bits and further increase compatibility and inverse compatibility between test vector and its reference vector.According to the statistics of shift state possible occurring,Huffman tree is built and the most optimal code form is found in coding process,so that the utilization ratios of short code words are increased and the use frequencies of long codes are decreased.The presented analysis and experiment results show that the proposed scheme can increase test data compression ratios and decrease test time with very low additional hardware overhead,and is superior to other existing run-length code schemes and similar blocking code ones.