Bounds on the Saved Area Ratio Due to PLA Folding

Folding is a scheme to reduce the silicon area in Programmable Logic Array (PLA) design. Since optimum folding is an NP-complete problem, methods for estimating potential area saving are desirable. In the case of row folding, both the upper and lower bounds for the saved area ratio d are derived in the paper. By applying the well-known Rent's relationship on a proposed partition model for PLA, we can show that [formula omitted] where r is the Rent's exponent in the range 0 ≤ r ≤ 1. Four examples are given to validate the theoretical prediction. Finally, possible refinement and open problems are also mentioned.