A Parallel Decimal Multiplier Using Hybrid Binary Coded Decimal (BCD) Codes

Abstract

A parallel decimal multiplier is proposed in this paper to improve performance by mainly exploiting the properties of three different binary coded decimal (BCD) codes, namely the redundant BCD excess-3 code (XS-3), the overloaded decimal digit set (ODDS) code and BCD-4221/5211 code, hence this design is referred to as hybrid. The signed-digit radix-10 recoding with the digit set {-5, 5} and the redundant BCD excess-3 (XS-3) representations are used for partial product (PP) generation. In this paper, a new decimal partial product reduction (PPR) tree is proposed, it consists of a binary PPR tree block, a nonfixed size BCD-4221 counter correction block and a BCD-4221/5211 decimal PPR tree block. Analysis and comparison using the logical effort model and 45 nm technology show that the proposed decimal multiplier is faster compared with previous designs found in the technical literature.