Design and implementation of PAL and PLA using reversible logic on FPGA SPARTAN 3E

Abstract

Reversible logic is the emerging field for research in present era. The aim of this paper is to design and synthesize a Programmable array Logic (PAL) and Programmable Logic array (PLA) using reversible logic with minimum quantum cost. The PAL is a Programmable Logic device which consists of programmable AND Gates and fixed OR gates array. The PLA is the PLD which contains programmable AND array and programmable OR array. The PLDs are the combinational circuits mainly used to realize Boolean functions on our interest. An n input and k output Boolean function f (a1, a2, a3,…. an) (referred as (n, k)) is said to be logically reversible if and only if, the number of inputs are equal to the number of outputs i.e., ‘n’ equals ‘k’ and the input pattern maps uniquely maps the output pattern. The reversible logic must run both forward and backward in such a way that the inputs can also be retrieved from outputs. There are many reversible logic gates in literature like NOT gate, Feynman Gate (CNOT gate), Double Feynman Gate, Peres Gate, TR gate, Seynman Gate and many more. Fan-out and Feed-back are not allowed in Logical Reversibility. To overcome the Fan out limitation, the signals from required output lines are duplicated to desired lines using additional reversible combinational circuits. Reversible Logic owns its applications in various fields which include Quantum Computing, Optical Computing, Nano-technology, Computer Graphics, low power VLSI etc., Reversible logic is gaining its own importance in recent years largely due to its property of low power consumption and low heat dissipation. In this paper, the design of PAL and PLA which has less heat dissipation and low power consumption is proposed. The designed circuits are analyzed in terms of quantum cost, garbage outputs and number of gates. The Circuit has been designed and simulated using Xilinx software and implemented on FPGA SPARTAN — 3E.