SPFD-Based Wire Removal in Standard-Cell and Network-of-PLA Circuits

Abstract

Wire removal is a technique by which the total number of wires between individual circuit nodes is reduced, either by removing wires or replacing them with other new wires. The wire removal techniques we describe in this paper are based on both binary and multivalued sets of pairs of functions to be distinguished (SPFDs). Recently, it was shown that a design style based on a multilevel network of approximately equal-sized programmable logic arrays (PLAs) results in a dense, fast, and crosstalk-resistant layout. This paper describes the application of SPFD-based wire removal techniques for circuit implementations utilizing networks of PLAs as well as standard-cells. In our first set of wire removal experiments (which utilize binary SPFD-based wire removal), we demonstrate that the benefit of SPFD-based wire removal is insignificant when the circuit is mapped using standard cells. We demonstrate that this technique is very effective in the context of a network of PLAs. In the next set of wire removal experiments, we focus only on circuits implemented using a network of PLAs. Three separate wire removal experiments are performed. Wire removal is invoked before clustering the original netlist into a network of PLAs, or after clustering, or both before and after clustering. For wire removal before clustering, binary SPFD-based wire removal is used. For wire removal after clustering, multivalued SPFD-based wire removal is used since the multioutput PLAs can be viewed as multivalued single output nodes. We demonstrate that these techniques are effective. The most effective approach is to perform wire removal both before and after clustering. Using these techniques, we obtain a reduction in placed and routed circuit area of about 11%. This reduction is significantly higher (about 20%) for the larger circuits we used in our experiments.