CARRY-PROPAGATE-ADDER

CARRYPROPAGATEADDERAMITHINGHERComputationalEngineeringBasicPrincipleofaCPA..Addstwon-bitoperandsA=(an-1..a0),B=(bn-1..b0)andanoptionalcarry-incinbyperformingcarrypropagationCanbeimplementedasacombinationalcircuitusingnfulladderscalledtheRippleCarryAdderARCHITECTUREa)LinearStructureb)TreeStructureARITHMETICEQUATION2ncout+S=A+B+cin2ncout+Σn-1i=02isi=Σn-1i=02iai+Σn-1i=02ibi+cin=Σn-1i=02i(ai+bi)+cin2ci+1+si=ai+bi+ci;I=0,1..n-1wherec0=cinandcout=cnLOGICALEQUATIONgi=aibipi=aibisi=piciCi+1=gi+pici;I=0,1…n-1wherec0=cin&cout=cnComplexityOfCPA!!!ComputationtimegrowslinearlywiththeoperandwordlengthnSpeedingupoperationofCPAwouldrequirereplacementbysomefasteradderstructure*(a)Symbol(b)RippleCarryimplementationofaCPACPA(CarrypropagateAdder)VsCSA(CarrySaveAdder)*AfouroperandaddercircuitComparison(CPAvsCSA)Thetworesultingadderarraysaresimilarinhardwarerequirements,logicstructureandcriticalpathlengthsBitarrivaltimeintheCPAisunequal(higherbitarriveslaterthanthelowerbits)ComparativelyslowWhyCarryPropagateAdder?PerformscarrypropagationfromeachbittohigherbitpositionsAdditionresultshavetobeconvertedtoirredundantintegerrepresentationDoesnotoccupyasignificantareaofthechipLessPowerConsumption