يك جمع كننده پيمانه 2N+1 يك گامي مبتني بر نمايش بيت كم ارزش دوتايي از مانده ها

A One-Step Modulo 2n+1 Adder Based on Double-Isb Representation of Residues

Efficien t modulo 2n± I adders are desirab le for computerarit hmetic units based on residue number systems (RNS) with the opular moduli set {2n- 1,2n, 2n+ 1}. Regularn-bit ripple-carry adders or their fast equivalents are suitable for modul on addition . But for the othe r two moduli a co rrecting increment/decrement step besides the primaryn-bit addition is normally required. Several des ign efforts have tried to reduce the latency of the correcting step to a sma ll de lay no t dep endi ng on the word length n, leading to one-s tep modular addition schemes. These include the use of alternative encoding of residues (e .g ., dirninished-I representation of modul o 2n+ 1 numbers), customized (vs . ge neric ) adders (e .g., spec ialized parallel pre fix adders), or compound adders . In this paper we investi gate alternative modulo 2n+ 1 addition schemes , focus on ge neric one-s tep ad der des igns, and use the double- lsb repr esentation of modul o 2n+ I numbers. In a generic modular adder , the ce ntral ab strac t n-b it adde r may be replaced by any concrete adde r architecture meeting the desig ner ʹ s prescribed measures in time, area and power consumption.