Design of an improved scan cell for concurrent on-line testing

For a high reliability, on-line testing is efficient in detecting faults on the early stage. A novel scan cell is proposed based on the conventional scan cell, which can protect the operational status from being changed during test. The test process and the functional operation of sequential circuit go in parallel. With a flexible clock selection mechanism utilized, both non-concurrent test and concurrent test can be operated. Simulation results show that these circuits can be test on-line with moderate hardware redundancy, high stability, and negligible time redundancy.