A New Class of Sequential Circuits with Acyclic Test Generation Complexity

This paper introduces a new class of sequential circuits called acyclically testable sequential circuits which is wider than the class of acyclic sequential circuits but whose test generation complexity is equivalent to that of the acyclic sequential circuits. We also present a test generation procedure for acyclically testable sequential circuits and elaborate a design-for-test (DFT) method to augment an arbitrary sequential circuit into an acyclically testable sequential circuit. Since the class of acyclically testable sequential circuits is larger than the class of acyclic sequential circuits, the DFT method results in lower area overhead than the partial scan method and still achieves complete fault efficiency. Besides, we show through experiment that the proposed method contributes to lower test application time compared to partial scan method. Moreover, the proposed method allows at-speed testing while the partial scan method does not.