ABSTRACT:

The binary adder is that the essential part in most digital circuit designs together with digital signal processors (DSP) and microprocessor datapath units. As such, in depth research continues to be targeted on improving the powerdelay performance of the adder. In VLSI implementations, parallel-prefix adders are known to have the most effective performance.

Parallel-prefix adders (additionally known as carry-tree adders) are known to own the simplest performance in VLSI designs. However, this performance advantage does not translate directly into FPGA implementations because of constraints on logic block configurations and routing overhead. This paper investigates three types of carry-tree adders (the Kogge-Stone, sparse Kogge-Stone, and spanning tree adder) and compares them to the easy Ripple Carry Adder (RCA) and Carry Skip Adder (CSA). These styles of various bit-widths were implemented on a Xilinx Spartan 3E FPGA and delay measurements were made with a high-performance logic analyzer. Because of the presence of a quick carry-chain, the RCA designs exhibit better delay performance up to 128 bits. The carry-tree adders are expected to own a speed advantage over the RCA as bit widths approach 256.

In this project for simulation we have a tendency to use Modelsim for logical verification, and additional synthesizing it on Xilinx-ISE tool using target technology and performing placing & routing operation for system verification on targeted FPGA.