Novel approaches for fault detection in two-dimensional combinational arrays

This paper presents new approaches for the constant (C)-testability of orthogonal (two-dimensional) arrays of combinational cells. A novel testability condition referred to as CO-testability is introduced: a testing approach for CO-testability is fully characterized based on adding states to the table of a cell. A second approach is also proposed. this approach is based on adding a variable number of additional states to a cell with a known table. This approach requires at most (m+k+α)(n+k+α)( m/k+1)(n/k+1) tests, where m and n are the number of states in the two dimensions of signal flow, α=1(0) if (partial) fail observability is applicable to the state table and k is the variable number of additional states per direction (2⩽k⩽m.n). As an example, the proposed approaches have been applied to a two-dimensional array for maximum/minimum comparison