A New Design for Variable Latency Speculative E.C&D Han-Carlson Adder

Abstract

Variable latency adders have been recently proposed in literature. In variable latency adder unwanted interconnections also reduced compared with kogge-stone topology. Kogge-Stone adder consists of large number of black cells and many wire tracks. A variable latency adder employs speculation: the exact arithmetic function is replaced with an approximated one that is faster and gives the correct result most of the time, but not always. In order to detect the error, error detection network is also used. The approximated adder is augmented with an error detection network that asserts an error signal when speculation fails. Speculative variable latency adders to reduce average delay compared to traditional architectures.

This paper proposes a novel variable latency speculative adder based on Han-Carlson parallel- prefix topology which proposes the error detection network that reduces error probability compared to previous approaches. Several variable latency speculative adders, for various operand lengths, using both Han-Carlson and Kogge- Stone topology, have been synthesized using Xilinx 14.3. Obtained results show that proposed variable latency Han-Carlson adder used in high-speed application.