Design of 32 bit Parallel Prefix Adders

Abstract

In this paper, we propose 32 bit Kogge-Stone, Brent-Kung, Ladner-Fischer parallel prefix adders. In general N-bit adders like Ripple Carry Adders (slow adders compare to other adders), and Carry Look Ahead adders (area consuming adders) are used in earlier days. But now the most Industries are using parallel prefix adders because of their advantages compare to other adders. Parallel prefix adders are faster and area efficient. Parallel prefix adder is a technique for increasing the speed in DSP processor while performing addition. We simulate and synthesis different types of 32-bit prefix adders using Xilinx ISE 10.1i tool. By using these synthesis results, we noted the performance parameters like number of LUTs and delay. We compare these three adders in terms of LUTs (represents area) and delay values. Keywords− prefix adder, carry operator, Kogge-Stone, Brent-Kung, Ladner-Fischer. I. Introduction Arithmetic circuits are the ones which perform arithmetic operations like addition, subtraction, multiplication, division, parity calculation. Most of the time, designing these circuits is the same as designing muxers, encoders and decoders. In electronics, an adder or summer is a digital circuits(7) that performs addition of numbers. In many computers and other kind of processors, adders are other parts of the processor, many computers and other kinds of processors, where they are used to calculate addresses, table and similar. The binary adder(7,10) is the one type of element in most digital circuit designs including digital signal processors(DSP) and microprocessor data path units. Therefore fast and accurate operation of digital system depends on the performance of adders (6). Hence improving the performance of adder is the main area of research in VLSI(10) system design. The Conventional adders discussed in section II. The details of R Kogge- Stone adder, Brent-Kung adder and Ladner- Fischer adders are discussed, and the implementation of proposed system is described in section III. The performance and simulation results were presented and discussed in section IV.