On the use of signed digit arithmetic for the new 6-inputs LUT based FPGAs

In this paper the use of signed digit (SD) arithmetic to better exploit some of the architectural characteristic of the last generation FPGAs is presented. The implementation of Radix-4 SD adders, multipliers and Finite Impulse Response (FIR) filters has been carried out to demonstrate that the use of this number system representation optimally fits the 6-input LUT Logic Elements (LEs) of the newest FPGAs architectures. Comparisons of implementations of the same circuits by using 4-input LUT and 6-input LUT based FPGAs have been carried out showing that Radix-4 SD arithmetic is very efficiently implemented in the last generation FPGAS.