一种基于FDR的高测试质量测试压缩方法

FDR编码方法有效地降低了测试数据量,但其测试集中的无关位全部填充为0,平均每个测试向量检测的故障数目较少,测试质量较低.为了提高测试质量,并进一步提高测试数据压缩率,本文基于FDR方法提出了一种利用上一个测试向量的响应填充该测试向量中无关位的测试压缩方法.该填充方法提高了测试向量中无关位填充的随机性,从而提高了测试集的测试质量.提出方法的压缩效率与测试向量的顺序有关,基于最近邻居算法对测试集进行排序,降低了测试响应与下一个测试向量之间不相同的位数,对测试响应和测试向量差分处理后再进行FDR编码,从而降低了测试数据量.ISCAS’89电路中几个大电路的实验结果表明,与FDR相比该方法的测试质量平均提高了5.9%,测试数据压缩率平均提高了2.5%,而只需要增加一个异或门的硬件开销.

A High Test Quality Test Compression Method Based on FDR Codes

FDR codes can compress test stimuli data effectively. However, the number of faults detected by a test pattern is small in average, since don't care bits in the test set are filled by all 0s. The test quality is low. In order to improve the test quality and further increase the test compression ratio, this paper, based on FDR codes, proposed a scheme in which the test response of the previous test pattern is utilized to fill the don't care bits in the current test pattern. This scheme increases the randomness of the X-filling. Therefore, the test quality is improved. In this scheme, the test compression ratio is also related to the order of test patterns. This paper also proposed a test pattern reordering approach based on the nearest neighbor algorithm to decrease the number of conflict bits between the test response of the previous test pattern and the current test pattern. Difference vectors can be obtained by the difference between test patterns and the test responses of their previous test patterns. The test data volume can be reduced by using FDR codes for the difference vectors. Experiment results show that, for larger ISCAS'89 circuits, the proposed approach increases the test quality by 5.9% and test compression ratio by 2.5% in average, compared with those of FDR codes. The hardware overhead, which is only an XOR gate, can be omitted.