Interleaved method and circuitry for testing for stuck open faults

摘要

A method and apparatus are disclosed for testing for stuck open faults in integrated circuits (10) having a plurality of combinational logic devices (18, 20). The apparatus includes a chain or shift register stages (22), with each stage including at lest two latches (L1and L2). Provision (43) is made for interleaving the bits of an initialization test pattern (40) with the bits of a detection test pattern (42) prior to loading the resultant serial data stream into the shift register stages (22). Once loaded, the latches (L2) contain the initialization test pattern whereas the latches (L1) hold the detection test pattern. A multiplexer (52) is provided for selecting one of the outputs from the two latches (L1, L2) so that the initialization test pattern and then the detection test pattern can be quickly applied to the combinational logic so as to minimize hazards which could invalidate the test results.