Linear and constant testability of hexagonally connected arrays

Testability conditions for two-dimensional hexagonal arrays are introduced. Conditions that permit testing of hexagonally connected arrays in time proportional to the number of cells are given. Design for testability of cells that allows constant testability to be achieved is proposed. Additional states are included in the state transition table of a cell. These states achieve full controllability and observability of the test results by regenerating the test input and propagating to the primary outputs the faulty states. The approach presented is less restrictive than previous ones