Much work has been done in deriving techniques to test unilateral Iterative Logic Arrays (ILAs). It is possible, under certain conditions, to test a unilateral ILA in time independent of the number of cells. This paper extends this work to bilateral ILAs, and presents conditions for the testing of bilateral ILAs in time proportional to the square of the size of the array, as well as conditions for testing in time linear to the size of the array.

The conditions for each case are observability and controllability requirements for the performance of each cell in the array. For instance, some of the most basic controllability conditions are that each right and left output can be set to any value. A basic observability condition is that different input values can produce different output values.

This work is interesting in beginning to extend the results for unilateral arrays to the bilateral case. Two examples are given: one for a one-dimensional array for FIR filtering, and another for a two-dimensional array that can be used for matrix multiplication. The definitions and proofs are unusually understandable, and this paper is of above average readability. Finally, the paper is interesting as an example of how stronger testability conditions can be rigorously shown to lead to shorter tests.