【文档说明】第4章计算机学科基础课件.ppt，共(42)页，560.665 KB，由小橙橙上传

转载请保留链接：https://www.ichengzhen.cn/view-76418.html

以下为本文档部分文字说明：

第4章计算机学科基础4–2ChapterGoals本章目标•Identifythebasicgatesanddescribethebehaviorofeach识别基础的门，描述每种门的行为•Describehowgatesareimplementedusin

gtransistors描述如何用晶体管实现门•Combinebasicgatesintocircuits用基础门组合电路4–3ChapterGoals本章目标•Describethebehaviorofagateorcir

cuitusingBooleanexpressions,truthtables,andlogicdiagrams用Boolean表达式、真值表和逻辑框图描述门或电路。•Compareandcontrastahalfadderandafulladder比较半加器和全加器之间的异同点•Desc

ribehowamultiplexerworks描述多路复用器是如何工作的4–4ChapterGoals本章目标•ExplainhowanS-Rlatchoperates解释如何操作S-R锁存器•Describethecharacteristicsofthefourthge

nerationsofintegratedcircuits描述第四代集成电路的特征4–5ComputersandElectricity计算机和电学•GateAdevicethatperformsabasicoperationonelectricalsign

als门是对电信号执行基础运算的设备。•CircuitsGatescombinedtoperformmorecomplicatedtasks电路是由门组合而成的，可以执行更加复杂的任务。4–6Computer

sandElectricity计算机和电学•Therearethreedifferent,butequallypowerful,notationalmethodsfordescribingthebehaviorofgatesandcircuits描述门和电路的表示法有三种，

它们互不相同，但却一样有效：–BooleanexpressionsBoolean表达式–logicdiagrams逻辑框图–truthtables真值表4–7ComputersandElectricity计算机和电学•BooleanexpressionsExpressionsi

nBooleanalgebra,amathematicalnotationforexpressingtwo-valuedlogic布尔表达式，布尔代数中的表达式，表示二值逻辑的数学表示法。Thisalgebraicnotationareaneleg

antandpowerfulwaytodemonstratetheactivityofelectricalcircuits这种代数表示法是演示电路活动的极好方式。4–8ComputersandElectricity计算机和电学•L

ogicdiagramAgraphicalrepresentationofacircuitEachtypeofgateisrepresentedbyaspecificgraphicalsymbol逻辑框图，一种电路的图形化表示，每种类型的

门有自己专用的符号。•TruthtableAtableshowingallpossibleinputvalueandtheassociatedoutputvalues真值表，列出了所有可能的输入值和输出值的表。4–9Gates门•Let

’sexaminetheprocessingofthefollowingsixtypesofgates我们将分析下列6种类型的门–NOT非门–AND与门–OR或门–XOR异或门–NAND与非门–NOR或非门4–10NOTGate非门•AN

OTgateacceptsoneinputvalueandproducesoneoutputvalue非门接受一个输入值，生成一个输出值。Figure4.1Variousrepresentationso

faNOTgate4–11NOTGate非门•Bydefinition,iftheinputvalueforaNOTgateis0,theoutputvalueis1,andiftheinputvalueis1,theoutputis0

根据定义，如果非门的输入值是0，那么输出值是1；如果输入值是1，那么输出值是0.•ANOTgateissometimesreferredtoasaninverterbecauseitinvertstheinputvalue非门有时候又叫反向器，因为它将对输入值求反

。4–12ANDGate与门•AnANDgateacceptstwoinputsignals与门接受两个输入信号•IfthetwoinputvaluesforanANDgateareboth1,theoutputis1;otherwise,theoutpu

tis0如果两个输入值全是1，则输出位1，其它情况均位0.Figure4.2VariousrepresentationsofanANDgate4–13ORGate或门•Ifthetwoinputvaluesareboth0,

theoutputvalueis0;otherwise,theoutputis1如果两个输入值均为0，则输出值位0，其它情况的输出值均为1.Figure4.3VariousrepresentationsofaORgate4–14XORGate异或门•XOR,ore

xclusiveOR,gate–AnXORgateproduces0ifitstwoinputsarethesame,anda1otherwise如果异或门的两个输入相同，则输出0；否则输出1–Notethedifferencebetw

eentheXORgateandtheORgate;theydifferonlyinoneinputsituation–Whenbothinputsignalsare1,theORgateproducesa1and

theXORproducesa04–15XORGate异或门Figure4.4VariousrepresentationsofanXORgateNANDandNORGates与非门和或非门•TheNANDandNORgat

esareessentiallytheoppositeoftheANDandORgates,respectivelyFigure4.5VariousrepresentationsofaNANDgateF

igure4.6VariousrepresentationsofaNORgate4–154–17ReviewofGateProcessing门处理回顾•ANOTgateinvertsitssingleinputvalue非门将对它的唯一输入值取反。•AnANDgateproduces1if

bothinputvaluesare1如果两个输入都是1，与门将生成1.•AnORgateproduces1ifoneortheotherorbothinputvaluesare1如果一个输入值是1，或者两个输入都是1，或

门将输出1.4–18ReviewofGateProcessing门处理回顾•AnXORgateproduces1ifoneortheother(butnotboth)inputvaluesare1如果只有一个输入值是1，而不是两个都是1

，异或门将输出1.•ANANDgateproducestheoppositeresultsofanANDgate与非门生成的结果和与门生成的相反•ANORgateproducestheoppositeresultsofanORgate或非门生成

的结果和或门生成的相反4–19GateswithMoreInputs具有更多输入的门•Gatescanbedesignedtoacceptthreeormoreinputvalues门可以设计成接受三个或更多个输入值。•Athree-inputANDgate,forexample,produce

sanoutputof1onlyifallinputvaluesare1例如，具有三个输入值的与门，只有当三个输入值都是1时，才生成值为1的结果。Figure4.7Variousrepresentationsofathree-inputANDgate4–20Cons

tructingGates门的构造•TransistorAdevicethatacts,dependingonthevoltagelevelofaninputsignal,eitherasawirethatconductselectricityorasaresistorthatbl

ockstheflowofelectricity晶体管根据输入信号的电压电平分为两种角色，一种是传导电流的导线，另一种是阻止电流的电阻。–Atransistorhasnomovingparts,yetactslikeaswitch虽然晶体管没有可移动的部分，但是却可以作为开关–Itismadeo

fasemiconductormaterial,whichisneitheraparticularlygoodconductorofelectricity,suchascopper,noraparticularlygoodinsul

ator,suchasrubber它是由半导体材料制成，所谓半导体材料，就是既不是像铜那样的良好导体，也不是像橡胶一样的绝缘体。4–21jasonm:Redo4.8(crop)ConstructingGates门的构造•Atransistorhasthreeterminals–

Asource源极–Abase基极–Anemitter,typicallyconnectedtoagroundwire发射极，通常接地•Iftheelectricalsignalisgrounded,

itisallowedtoflowthroughanalternativeroutetotheground(literally)whereitcandonoharmFigure4.8Theconnectionso

fatransistor4–22ConstructingGates门的构造•Itturnsoutthat,becausethewayatransistorworks,theeasiestgatestocreateareth

eNOT,NAND,andNORgatesFigure4.9Constructinggatesusingtransistors4–23Circuits电路•Twogeneralcategories–Inacombinationalcircuit,theinputval

uesexplicitlydeterminetheoutput组合电路，输入值明确决定输出值。–Inasequentialcircuit,theoutputisafunctionoftheinputva

luesaswellastheexistingstateofthecircuit时序电路，输出值是输入值和电路现有状态的函数。•Aswithgates,wecandescribetheoperationsofentirecircuitsusingthreenotations–Booleane

xpressions–logicdiagrams–truthtables4–24CombinationalCircuits组合电路•Gatesarecombinedintocircuitsbyusingthe

outputofonegateastheinputforanother把一个门的输出作为另一个门的输入，可以把门组合成电路。Page994–25CombinationalCircuits组合电路•Becausetherearethreeinputsto

thiscircuit,eightrowsarerequiredtodescribeallpossibleinputcombinations•ThissamecircuitusingBooleanalgebrais(AB+AC)Page1004–26Nowlet’sgotheo

therway;let’stakeaBooleanexpressionanddraw•ConsiderthefollowingBooleanexpressionA(B+C)Page100Page101•Nowcomparethefinalresu

ltcolumninthistruthtabletothetruthtableforthepreviousexample•Theyareidentical4–27Nowlet’sgotheotherway;let’stakeaBooleanexp

ressionanddraw•Wehavethereforejustdemonstratedcircuitequivalence电路等价–Thatis,bothcircuitsproducetheexactsameoutputforeachin

putvaluecombination–对应每个输入值组合，两个电路都生成完全相同的输出。•Booleanalgebraallowsustoapplyprovablemathematicalprinciplestohelpusdesignlogicalcircuits布尔

代数允许我们使用已经证明的数学法则来设计逻辑电路。4–28PropertiesofBooleanAlgebra布尔代数属性Page101交换律结合律分配律恒等余式4–29Adders加法器•Atthedigitallogiclevel,additionisperformedinb

inary在数字逻辑层，加法是用二进制执行的。•Additionoperationsarecarriedoutbyspecialcircuitscalled,appropriately,adders加法运算是由专用的电路加法器执行的。4–30Adders加法器•Theresultof

addingtwobinarydigitscouldproduceacarryvalue•Recallthat1+1=10inbasetwo•Acircuitthatcomputesthesumoftwobitsandproducesthecorrectcarrybiti

scalledahalfadderPage103计算两个数位的和，并生成正确的进位的电路称为半加器。4–31Adders加法器•Circuitdiagramrepresentingahalfadder•T

woBooleanexpressions:sum=ABcarry=ABPage1034–32Adders加法器•Acircuitcalledafulladdertakesthecarry-invaluein

toaccount计算两个数位的和，并考虑进位输入的电路叫全加器。Figure4.10Afulladder4–33Multiplexers多路复用器•Multiplexerisageneralcircuitthatproducesasingle

outputsignal多路复用器是生成单一输出信号的通用电路–Theoutputisequaltooneofseveralinputsignalstothecircuit–输出值等于该电路的多个输入值之一–Them

ultiplexerselectswhichinputsignalisusedasanoutputsignalbasedonthevaluerepresentedbyafewmoreinputsignals,ca

lledselectsignalsorselectcontrollines–多路复用器根据称为选择信号或者选择控制线的输入信号选择用哪个输入信号作为输出信号4–34Multiplexers多路复用器•ThecontrollinesS0,S1,a

ndS2determinewhichofeightotherinputlines(D0throughD7)areroutedtotheoutput(F)Figure4.11Ablockdiagramofamultiplexerwiththrees

electcontrollinesPage1054–35CircuitsasMemory存储器电路•Digitalcircuitscanbeusedtostoreinformation数字电路可以用来

存储信息•Thesecircuitsformasequentialcircuit,becausetheoutputofthecircuitisalsousedasinputtothecircuit这些电路是时序电路，因为这种电路的

输出信号也被用作电路的输入信号4–36CircuitsasMemory存储器电路•AnS-Rlatchstoresasinglebinarydigit(1or0)S-R锁存器存储一个二进制位•ThereareseveralwaysanS-Rlatchc

ircuitcouldbedesignedusingvariouskindsofgatesFigure4.12AnS-Rlatch4–37CircuitsasMemory存储器电路•Thedesignofthiscircuitguaranteesthatth

etwooutputsXandYarealwayscomplementsofeachother•ThevalueofXatanypointintimeisconsideredtobethecurrentstateofthecircuit•Therefore,ifXis

1,thecircuitisstoringa1;ifXis0,thecircuitisstoringa0Figure4.12AnS-Rlatch4–38IntegratedCircuits集成电路•Integratedcircuit(alsocalledachip)Apie

ceofsilicononwhichmultiplegateshavebeenembedded集成电路是嵌入了多个门的硅片Thesesiliconpiecesaremountedonaplasticorceramicpackagewithpinsalongtheedges

thatcanbesolderedontocircuitboardsorinsertedintoappropriatesockets这些硅片被封装在塑料或者陶瓷中，边缘有引脚，可以焊接在电路板上或者插入适合的插座中。4–39IntegratedCircuits集成电路•Integratedci

rcuits(IC)areclassifiedbythenumberofgatescontainedinthemPage1074–40IntegratedCircuits集成电路Figure4.13AnSSIchipcontainsind

ependentNANDgates4–41CPUChipsCPU芯片•ThemostimportantintegratedcircuitinanycomputeristheCentralProcessingUnit,orCPU中央处理器•EachCPUchiphasa

largenumberofpinsthroughwhichessentiallyallcommunicationinacomputersystemoccurs每个CPU芯片都有大量的引脚，计算机系统的所有通信都是通过这些引脚完成的。