Systems and methods for improved scan testing fault coverage

Abstract

Systems and methods for improved fault coverage of logic built-in-self-tests (LBISTs) in integrated circuits (ICs) which ensure testing of specific logic by forcing specific values into scan latches that contain otherwise pseudorandom test bit patterns. In one embodiment, an LBIST system comprises a plurality of scan latches and forcing logic coupled to a first set of the scan latches which provide inputs to selected target logic. The forcing logic is configured to overwrite values stored in the first set of scan latches with desired values. In one embodiment, the forcing logic includes a bypass path that enables shifting of unaltered bit patterns around the first set of scan latches. Bits in the bypass path may be inverted when the bypass path is not being used in order to help detect errors in the operation of the bypass path.