提出了一种新的基于游程编码的测试数据压缩/解压缩的算法:共游程码(SRLCS)编码,它在使用较短的代码字来代替较长的游程的传统游程编码基础上,进一步充分利用了相邻游程之间的相关性,使用一位来代替与前一游程相同的整个后一游程,这样整个后一游程可以用一位来表示,达到从多位到一位的转换,进一步压缩了测试数据.由于测试数据中存在大量的无关位,对无关位适当的赋值,可以增加连续游程长度相同的概率,提出了一种针对共游程码的无关位填充算法.理论分析和实验结果证明该方案具有高数据压缩率、硬件实现简单等特点.
One of the major challenges in testing integrated circuits is dealing with the large test data size. To reduce the volume of test data, several test data compression schemes have been presented. But all of these schemes do not explore the relationship between consecutive runs. So a new scheme of test data compression/decompression, namely sharing-run-length code scheme (SRLCS) is presented, which is based on run length coding. It explores further the relationship between consecutive runs on the basis of traditional run length coding characteristic which uses shorter eodeword to represent longer run length. Thus, only 1 bit needs to represent the whole later run in immediate two runs whose lengths are the same in this scheme. ATPG tools generate test patterns with many don't care bits, which are 95% to 99% of the bits in test data for large industrial circuits. So filling the don't care bits in test data appropriately can increase the probability of the consecutive runs whose lengths are the same. A strategy of filling don't care bits is also proposed for this scheme. Compared with other schemes, this scheme has some characteristics, such as high compression ratio and easy control and implementation. Theoretical analysis and experimental results for the Mintest test set of ISCAS- 89 benchmark circuits show that the proposed scheme is a very efficient compression method.