268VLSI Test Principles and Architecturesknown value. This can be accomplished by adding a 0-control point, 1-control point,bypass logic, or control-only scan point. We recommend the latter two approachesbecause they yield higher fault coverage than the former two approaches.188.8.131.52Memories and Non-Scan Storage ElementsExamples of memories aredynamic random-access memories(DRAMs),staticrandom-access memories(SRAMs), or flash memories. Examples of non-scan stor-age elements are D flip-flops or D latches. Bypass logic is typically used to blockeach unknown (X) value originating from a memory or non-scan storage element.Another approach is to use an initialization sequence to set a memory or non-scanstorage element to a known state. This is typically done to avoid adding delay tocritical (functional) paths. Care must be taken to ensure that the stored state is notcorrupted throughout the BIST operation.
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