Automated Optimization of Scan Chain Structure for Test Compression-Based Designs
Harshad Dhotre, Mehdi Dehbashi, Ulrike Pfannkuchen, Hofmann Klaus · 2016
Test compression hardware blocks such as EDT are utilized in large industrial designs to compress scan test data in order to decrease scan test time and volume. During pattern generation for EDT-based designs, some faults cannot be detected due to linear dependency and insufficient encoding capacity of EDT. These faults called EDT Aborted (EAB) faults cause a notable coverage loss in some designs. In this work, a new approach is proposed to form scan chains such that the number of EAB faults decreases and the test coverage increases. The approach places scan flipflops corresponding to care bits at appropriate positions in order to reduce linear dependency during pattern generation. The approach is totally automated and has been integrated into the existing design flow. The experimental results on the industrial designs show that the new approach decreases the number of EAB faults significantly and achieves a high test coverage.