Design of check tests for digital units through cubic covering

A new method is proposed of design of check tests for digital units by specification of functions to be implemented as their cubic coverings. Unity and zero coverings of a combinational unit are obtained simultaneously through direct substitution. The resultant cubes preserve the output values of internal elements. A test design procedure is formulated and proved sound for checking constant faults of element and unit outputs. The method is extended to a unit with memory, the unit being represented as a logical network where the elements are associated with signal propagation delays. An iterative covering generation procedure is developed which does not require identification of feedbacks. Check tests are designed from the resultant coverings.