California scan architecture for high quality and low power testing

This paper presents a scan architecture - California scan - that achieves high quality and low power testing by modifying test patterns in the test application process. The architecture is feasible because most of the bits in the test patterns generated by ATPG tools are don't-care bits. Scan shift-in patterns have their don't-care bits assigned using the repeat-fill technique, reducing switching activity during the scan shift-in operation; the scan shift-in patterns are altered to toggle-fill patterns when they are applied to the combinational logic, improving defect coverage.