Built-in generation of multicycle functional broadside tests with observation points

Abstract

Functional broadside tests allow overtesting to be avoided as part of a scheme that considers both test generation and the analysis of output responses, by ensuring that delay faults are detected under functional operation conditions. Compared with two-cycle tests, multicycle tests allow more faults to be detected with each test, thus reducing the number of tests that need to be applied. They also provide an opportunity for nonfunctional electrical effects, which are caused by switching between modes of operation, to subside before the clock cycles where delay faults are detected. Built-in test generation facilitates at-speed testing and reduces the test data volume. Motivated by these observations, this article describes the modification of a built-in test generation method for two-cycle functional broadside tests so as to generate multicycle functional broadside tests. The size of the hardware is not increased by the modification. The article investigates the following issues related to this method: (1) the effect of using multicycle tests on the number of tests that need to be applied; (2) fault simulation for tailoring the test generation hardware to a circuit that takes into account, to different extents, the need to allow nonfunctional electrical effects to subside; (3) the insertion of observation points in order to increase the transition fault coverage.