Arithmetic Circuits Combining Residue and Signed-Digit Representations

This paper discusses the use of signed-digit representations in the implementation of fast and efficient residue-arithmetic units. Improvements to existing signed-digit modulo adders and multipliers are suggested and new converters for the residue signed-digit number system are described for the moduli {2 n -1,2 n ,2 n +1}. By extending an existing efficient signed-digit adder design to handle modulo operations, we are able to implement high performance modulo addition. The hardware complexity of signed-digit modulo multipliers is reduced by using a more efficient algorithm for calculating partial products. Finally, the novel converters presented makes it possible to integrate this residue signed-digit number system with conventional binary circuits.