Test Data and Test Time Reduction for LOS Transition Test in Multi-Mode Segmented Scan Architecture

Launch-off-Shift (LOS) is a widely used technique for delay test in scan-based design. Test data compression for LOS patterns, however, is less efficient. In this paper, we first analyze the reason for low compression rate in LOS patterns, and present an LOS test enabled scan architecture that supports three operation modes: broadcast, multicast, and serial. Efficient LOS test data compression can be achieved under this architecture with limited hardware overhead. An ATPG method for LOS test patterns under the proposed architecture is also presented. Experimental results show that most of the serial scan operations can be replaced by multicast operations, and thus achieve much better compression rate.