An improved scan cell ordering method using the scan cells with complementary outputs

Scan-based testing always consumes considerable power due to the transitions during the shifting of test data in scan chain. Scan cell ordering technique is effective in reducing such transitions. In this paper, we propose an improved scan cell ordering method. We introduce the scan cells with complementary outputs to enable two alternative connection styles between scan cells during the process of scan cell ordering. This can further reduce the transitions during test application and save more test power. We applied this method on several benchmark circuits. The results show that the number of transitions due to the scan chain by our proposed method is 39.0% fewer than that of the original scan design on average. Compared with the method based on all scan cells connected in a uniform connection style, our method can achieve the scan designs with 4.5% fewer of transitions averagely. Also, with regard to saving test power, the proposed method is superior to that only considers two connection styles after scan cell ordering.