Constant Multipliers for FPGAs

摘要

This paper presents a survey of techniques to implement multiplications by constants on FPGAs. It shows in particular that a simple and well-known technique, canonical signed recoding, can help design smaller constant multiplier cores than those present in current libraries. An implementation of this idea in Xil-inx JBits is detailed and discussed. The use of the latest algorithms for discovering optimal chain of adders, subtracters and shifters for a given constant multiplication is also discussed. Exploring such solutions is made possible by the new FPGA programming frameworks based on generic programming languages, such as JBits, which allow an arbitrary amount of irregularity to be implemented even within an arithmetic core.