Easily Testable Iterative Logic Arrays

Iterative logic arrays (ILA) are studied with respect to two testing problems. First, a variety of conditions are presented which, when met, guarantee an upper bound on the size of the test set for the ILA under consideration. Second, techniques are presented for designing optimally testable ILA's. The arrays that are treated are, in some cases, more general than those that have been reported by other researchers: they include multidimensional and inhomogeneous arrays. Octagonally-connected arrays, hexagonally-connected arrays, and bilateral arrays also are discussed. The presented results indicate that the characteristics of the individual cell functions (e.g., whether they are bijective) are a good guide to the test complexity of the overall array. Matrix multiplication, as an example, is shown to have several different optimally testable implementations. The results are useful for combinational and pipelined arrays, and for certain systolic arrays.