Orthogonal scan: low overhead scan for data paths

Orthogonal scan paths, which follow the path of the data flow, can be used in data path designs to reduce the test overhead-area, delay and test application time by sharing functional and test logic. Orthogonal scan paths are orthogonal to traditional scan paths. Judicious ordering of the registers in the orthogonal scan path can allow the scan path to be implemented entirely with existing interconnect, resulting in no additional wiring to connect the scan path and no performance degradation due to additional loading on the bistable outputs. Taking the orthogonal scan path into account during high-level synthesis operations such as register allocation allows for a better final solution, but orthogonal scan paths can also be used with non-synthesized data path. Orthogonal scan paths have roughly half the overhead of traditional scan paths and greatly reduce the test application time. TOPS, Stanford CRC´s synthesis-for-test tool, has been modified to implement orthogonal scan paths for synthesized circuits