組合邏輯電路分析和設(shè)計(jì)

CHAPTER5

CombinationalLogicAnalysisandDesign（組合邏輯電路分析和設(shè)計(jì)）組合邏輯電路時(shí)序邏輯電路components：LogicGatesCombinationallogiccircuitSequentiallogiccircuitcomponents：LogicGates+FlipFlops,LatchesChapter7,8,9,10Chapter5,6theoutputisonlydependedonthecurrentinputsTheoutputisnotonlydependedonthecurrentinputsbutalsodependedonthepaststateCombinationallogiccircuitchapter5chapter6CombinationallogicAnalysisandDesignFunctionsofcombinationalLogic5-1BasicCombinationalLogicCircuits5-2CombinationalLogicCircuits

Analysis5-3ImplementingCombinationalLogic

5-4TheUniversalPropertyofNANDandNORGates

5-5CombinationalLogicUsingNANDandNORGates5-6LogicCircuitOperationWithPulseWaveformCHAPTER5CombinationalLogicAnalysisandDesignAND-ORLogic（與-或邏輯電路）AND-OR-InvertLogic（與-或-非邏輯電路）Exclusive-ORLogic（異-或邏輯電路）5-1BasicCombinationalLogicCircuitsAND-ORLogicTruthtableINPUTSABCDABCDOUTPUTX0000000100100011010001010110011110001001101010111100110111101111000000010000000100000001101010110001000100011111XX=AB+CDAND-ORLogicAND-ORInvertLogicExclusive-ORLogicABX000110110110TruthtableExclusive-NORLogic

BooleanexpressionTruthtableTwoequivalentwaysofimplementingtheexclusive-NOR

Samelogiccanbeimplementedbydifferentcircuit5-2CombinationalLogicCircuitsAnalysis

(組合邏輯電路分析)LogicCircuitLogicFunctionX=F(A,B,C)?ThesensorproduceaHIGHwhenthelevelofchemicalinthetankdropsbelowaspecifiedpointBCABACA,B,Carelevelsensors.aHIGHisproducedwhenthelevelofchemicalinthetankdropsbelowaspecifiedpoint.AnalysisthefunctionofthecircuitX=AB+BC+ACBCABACX=AB+BC+ACTruthtableABCABBCACX00000101001110010111011100000000001000000110011100010111Thelow-levelindicatorwillgiveanindicationwhenmorethantwotanks’leveldropbelowthespecifiedpoint!AnalysisthefunctionofthecircuitAnalysisthefunctionofthecircuit(review)

Step1:ObtaintheLogicExpressionfromthelogiccircuitStep2:ConstructingaTruthTablefortheLogiccircuitStep3:Analysisthefunction

5-3ImplementingCombinationalLogic

（組合邏輯電路的設(shè)計(jì)）LogicCircuitLogicFunction1.FromanapplicationtoaTruthTable2.FromaTruthTabletoasimplifiedlogicexpression3.FromthesimplifiedlogicexpressiontoalogiccircuitExample：Implementavotingcircuitforthreeperson.Eachpersonhasonebutton.Pressthebuttonforagreementandleaveitfordisagreement.TheoutputwillshowonaLEDlight.Thelightonwhenmajoritypeopleagreed.Otherwise,thelightoff.三人表決電路每人一個(gè)按鍵，如果同意則按下，不同意則不按。結(jié)果用指示燈表示，多數(shù)同意時(shí)指示燈亮，否則不亮。FromlogicfunctiontoTruthTableTruthTableInputs:A、B、CAgree“1”，otherwise“0”O(jiān)utput:FLighton“1”，otherwise“0”Implementavotingcircuitforthreeperson(A、B、C):

Eachpersonhasonebuttoninfrontofhim.Pressthebuttonforagreementandleaveitfordisagreement.

TheoutputwillshowonaLEDlight.Thelightonwhenmajoritypeopleagreed.Otherwise,lightoff.

TruthTable2.FromTruthTabletosimplifiedlogicexpressionABC0001111001ABACBCABBCCAF3.FromLogicExpressiontoLogicCircuitAnd-OrLogic3.FromLogicExpressiontoLogicCircuitchap5-1a.ewbImplementathreeinputsparitychecker:Theoutputis“1”whenthenumberofinput“1”isodd.

(1)TruthTable

(2)Logicexpression

0000

A

B

C

Y0011010101101001101011001111ABC00100111101111Solution：奇偶檢驗(yàn)器

(3)logiccircuit

(3)logiccircuitChap5奇偶校驗(yàn)電路.ewbstep1.FromanapplicationtoaTruthTablestep2.FromaTruthTabletoasimplifiedlogicexpressionstep3.FromthesimplifiedlogicexpressiontoalogiccircuitCombinationLogicImplementation(Review)LogicCircuitLogicFunctionTextbook:Page168ch5-25-3TheUniversalProperty

ofNANDandNORGates

NANDandNORgatesare“universal”becausetheycanusedtoproduceanyoftheotherlogicfunctionsTheNANDGateasaUniversalLogicElementTheNORGateasaUniversalLogicElementNANDGateasanInverterTheNANDGateasaUniversalLogicElement?AAHIGH??NANDGateasanInverterxTwoNANDGatesasanANDGate?ThreeNANDGatesasanORGateFourNANDGatesasNORGateFourNANDGatesasXORGateNORGateasanInverterTheNORGateasaUniversalLogicElementTwoNORGatesasanORGateThreeNORGatesasanANDGateFourNORGatesasanNANDGateNANDlogicforX=AB+CD?5-4COMBINATIONALLOGICUSINGNANDANDNORGATEDeMorgan’s最簡(jiǎn)邏輯電路標(biāo)準(zhǔn)門的個(gè)數(shù)最少每個(gè)門的連線最少門的種類最少

NANDLogicDiagramsUsingDualsymbolswhendrawingaNANDlogicdiagram,alwaysusethegatesymbolsinsuchawaythateveryconnectionbetweenagateoutputandagateinputiseitherbubble-to-bubbleornonbubble-to-nonbubble.UseoftheappropriatedualsymbolsinaNANDlogicdiagrameveryconnectionbetweenagateoutputandagateinputiseitherbubble-to-bubbleornonbubble-to-nonbubbleEXAMPLE:ImplementeachexpressionwithNANDlogicusingappropriatedualsymbols(a)EXAMPLE:ImplementeachexpressionwithNANDlogicusingappropriatedualsymbols(b)NORLOGICNORnegative-ANDNORlogicforX=(A+B)(C+D)

ANORgatefunctionaseitheraNORoranegative-AND.180三人表決電路:

Implementavotingcircuitforthreeperson(A、B、C):UseNANDgatesABCAnd-OrLogicGatesABCNANDLogicGates最簡(jiǎn)邏輯電路標(biāo)準(zhǔn)門的個(gè)數(shù)最少每個(gè)門的連線最少門的種類最少Implementathreeinputsparitychecker:Theoutputis“1”whenthenumberofinput“1”isodd.奇偶檢驗(yàn)器(3)ConverttoNANDlogic

(2)LogicexpressionUseNANDGates!EX5-12：DeterminethefinaloutputwaveformXforthecircuit,withinputwaveformsA,BandCasshown.5-5CIRCUITOPERATIONWITHPULSEWAVEFORMINPUTSEX5-11：DrawthetimingdiagramFindoutthelogiccircuitthatwillgeneratetheoutputwaveformfortheinputs.inputsoutputABCX000Page193:Problem30Homework:Page193Problem31DigitalSystemApplication7-segmentdisplayspage149共陽(yáng)極接法共陰極接法gfedcba例：共陰極接法a

b

c

d

e

f

g

01100001101101低電平時(shí)發(fā)光高電平時(shí)發(fā)光共陽(yáng)極接法abcgdef+dgfecbag共陰極接法abcdefg二－十進(jìn)制編碼?顯示器件

D

C

BAa

b

c

d

efg00001111110000010110000100101101101200111111001301000110011401011011011501101011111601111110000710001111111810011