Abstract: The present invention relates to a test system (100) interposed between a clock monitor self-timed memory. In an example embodiment, the test system (100) receives an internal clock signal (104) from the clock monitor (152), an external clock signal (CL) and a control signal (CS). A multiplexer (110) of the test system provides in dependence upon the control signal (CS) the internal clock signal (104) to the internal memory block (125) during a normal mode of operation of the self-timed memory and the external clock signal (CL) to the internal memory block (125) during a test mode (108) of the self-timed memory. The test system (100) enables control of the clock cycle of the internal memory block (125) by directly applying the external clock signal (CL) during test mode. Thus, the internal memory block is stressed properly enabling the detection of small delay faults.

Abstract: Hard-open defects between logic gates of, for example, an address decoder and the voltage supply which result in logical and sequential delay behavior render a memory conditionally inoperative. A method and apparatus for testing integrated circuits for these types of faults is proposed, in which two cells of two logically adjacent rows or columns are written with complementary logic data. If a read operation reveals the data in the two cells to be identical, the presence and location of a hard-open defect is demonstrated.