Design of regular arrays

One of the underlying principles of engineering design is that we should attempt to reduce the complexity (and hence cost) of our designs by identifying and constructing subsystems which can then be repeated or replicated to form the complete system. In the context of digital systems we have already seen several examples of the application of this principle, including both combinational and sequential circuits, for example, ripple-carry adders, cascadable magnitude comparators, ripple countries, and shift registers. In all such cases, the regular iterative (or ‘repeating’) nature of the circuit refers to the structure, consisting of a number of identical subcircuits (‘cells’, or ‘modules’) linked to form an array which performs the overall function.