Parallel Prefix Adders

Design and Characterization of Parallel Prefix Adders using FPGAs David H. K. Hoe, Chris Martinez and Sri Jyothsna Vundavalli take apart of Electrical Engineering The University of Texas, Tyler dhoe@uttyler.edu ? AbstractParallel-prefix common vipers (also known as carry channelize common vipers) ar known to carry the best carrying into action in VLSI designs. However, this cognitive process advantage does not translate directly into FPGA implementations due to constraints on logic jampack configurations and routing overhead. This paper investigates three types of carry-tree common vipers (the Kogge-Stone, sparse Kogge-Stone, and spanning tree adder) and comp ares them to the mere(a) Ripple determine Adder (RCA) and run edit out Adder (CSA). These designs of alter bit-widths were implemented on a Xilinx ascetic 3E FPGA and hold in measurements were made with a high-performance logic analyzer. due to the figurehead of a fast carry-chain, the RCA designs exhibi t better delay performance up to 128 bits. The carry-tree adders are expected to have a locomote advantage over the RCA as bit widths move up 256. described. An efficient testing strategy for evaluating the performance of these adders is discussed. Several tree-based adder structures are implemented and characterized on a FPGA and compared with the Ripple Carry Adder (RCA) and the Carry Skip Adder (CSA). Finally, some conclusions and suggestions for improve FPGA designs to enable better tree-based adder performance are given. II. CARRY-TREE adder DESIGNS Parallel-prefix adders, also known as carry-tree adders, pre-compute the propagate and generate signals [1]. These signals are variously combine using the fundamental carry element (fco) [2]. (gL, pL) ? (gR, pR) = (gL + pLgR, pL pR) (1) Due to associative property of the fco, these operators can be combine in different ways to form various adder structures. For, example the four-bit carry-lookahead generator is given by : c4 = (g4, p4) ? [ (g3, p3) ? [(g2, p2) ? (! g1, p1)] ] (2) A unsophisticated rearrangement...If you want to get a full essay, order it on our website: BestEssayCheap.com

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