Design and Implementation of High Speed Hybrid Carry Select Adder

Adder is considered the principle unit of every arithmetic and logical operation. Carry select adder (CSLA) is an adder that helps to speed up operations of several arithmetic function. To further improve the speed, an idea of incorporating more than one high speed adder logic within a regular CSLA is employed. This paper discusses the design of a hybrid CSLA which utilizes the advantages of both Kogge Stone adder and look ahead adder (CLA) to obtain higher speed. Kogge Stone adder is a particular type of Adder and hence it is widely regarded as one of the high speed addition methods due to faster carry generation. Look ahead adders are employed in the initial stages of the modified adder to boost its speed as its computation performance is better if the number of bits are less. A 64-bit hybrid CSLA is implemented, in Xilinx Spartan 6 FPGA development board. The modified hybrid carry select adder is found to improve the speed and provides better results on energy requirement and speed compared to other carry select adders.