A testable design of iterative logic arrays

Testable design of unilateral iterative logic arrays (ILA) of combinational cells under the assumption of a single cell failure is considered. The concepts of one-step testability and one-step -testability are introduced. Methods to modify the basic cell flow table so as to facilitate fault detection and location are given. It is shown that if no directly observable outputs from each cell are available, then it is possible to augment the cell flow table by the addition of a fixed number of columns and a row so that a faulty cell can be located by a test of length proportional to , where is the number of cells in the array. However, if directly observable outputs are available from each cell, then the test length is shown to be independent of the array length to locate a faulty cell. A set of simpler sufficient conditions are given for the testability of two-dimensional arrays. It is shown that these conditions ensure that all possible input states can be applied to every cell in an array of arbitrary dimensions.