Signed multiplication technique by means of unsigned multiply instruction

The present work aims at proposing an efficient technique for signed binary multiplication using unsigned, multiply instruction. Numerous examples are provided to show efficiency of the proposed approach in the context of practical software implementation. Performance of the technique is compared to the software emulated versions of classical methods, such as radix-2 Booth method, reversal of sign method (negative to positive conversion) and sign extension method. The proposed algorithm is suitable for embedded systems which are based on widespread microprocessors/microcontrollers which have an unsigned multiplication in their instruction set but no signed multiply instruction. The algorithm includes only one unsigned multiplication and two subtractions. Various samples of code presenting the signed multiplication are provided in the assembly language for an MCS-51 compatible microcontroller. The comparison of the performance of algorithm is carried out for classical MCS-51 core and innovative AT89LPx core treated as a reference microcontroller.