6版 Project 5 課文及翻譯

電子與通信技術(shù)專業(yè)英語電子信息工程學(xué)院Project5

BasicLogicGatesBasicLogicGatesAlogicgateisabasicbuildingblockofadigitalcircuitthathastwoinputsandoneoutput.Thesegatesareimplementedusingelectronicswitchesliketransistors,diodes.基本邏輯門

邏輯門是具有兩個(gè)輸入和一個(gè)輸出的數(shù)字電路的基本部件。這些門是用晶體管、二極管等電子開關(guān)實(shí)現(xiàn)的。Thebasiclogicgatesareclassifiedintoseventypes:ANDgate,ORgate,XORgate,NANDgate,NORgate,XNORgate,andNOTgate.Thetruthtableisusedtoshowthelogicgatefunction.AllthelogicgateshavemorethanoneinputsexcepttheNOTgate,whichhasonlyoneinput.

基本邏輯門分為七種類型：與門、或門、異或門、與非門、或非門、異或非門和非門。用真值表表示邏輯門的功能。除了非門,所有邏輯門都有一個(gè)以上的輸入。非門只有一個(gè)輸入。ThethreemostcommonbasictypesofdigitallogicgatesaretheANDgate,theORgate,andtheNOTgate(asshowninFig.5-1).TheoperationofanANDgateismathematicallyexpressedbytheequationA×B=C.Thiscanbereadas“inputAandinputBequalsoutputC”.TheoperationofanORgateisoftenexpressedbytheequationA+B=C.Thiscanbereadas“eitherinputAorinputB(orboth)equalsoutputC”.AnimportantfunctionofNOTgateistoproducesignalinversionoranoutputsignalthatisoppositeinnaturetotheinputsignal.Anylogicfunctioncanbeperformedbythethreebasicgatesthathavebeendescribed.Eveninalargescaledigitalsystem,suchasacomputer,control,ordigital-communicationsystem,thereareonlyafewbasicoperations,whichmustbeperformed.Thethreebasictypesofdigitallogicgatesandtheflip-floparethefourcircuitsmostcommonlyemployedinsuchsystems.Fig.5-1DigitalLogicGates三種最常用的基本邏輯門是與門、或門和非門（如圖5-1所示）。與門運(yùn)算用數(shù)學(xué)等式可表示為A×B=C。它可以讀作“輸入A與輸入B等于輸出C”?；蜷T運(yùn)算常用方程A+B=C表示。它可以讀作“輸入A或輸入B（或兩者均有）等于輸出C”。非門的重要功能是產(chǎn)生反向信號(hào)，即產(chǎn)生與輸入信號(hào)性質(zhì)相反的輸出信號(hào)。任何一種邏輯功能都可用上述三種基本門電路來實(shí)現(xiàn)。即使是在大規(guī)模數(shù)字系統(tǒng)，例如計(jì)算機(jī)系統(tǒng)、控制系統(tǒng)或數(shù)字通信系統(tǒng)中，需要執(zhí)行的基本運(yùn)算也只有這幾種。三種基本類型的數(shù)字邏輯門和觸發(fā)器是此類系統(tǒng)中最常用的四種電路。Thebasiclogicgatesareusedtoperformfundamentallogicalfunctions.ThesearethebasicbuildingblocksinthedigitalICs(integratedcircuits).Mostofthelogicgatesusetwobinaryinputsandgeneratesasingleoutputlike1or0.Insomeelectroniccircuits,fewlogicgatesareusedwhereasinsomeothercircuits,microprocessorsincludemillionsoflogicgates.

基本邏輯門用來實(shí)現(xiàn)基本的邏輯功能，它們是數(shù)字IC（集成電路）中的基本組成部分。大多數(shù)邏輯門使用兩個(gè)二進(jìn)制輸入，并產(chǎn)生1或0這樣的單個(gè)輸出。在有些電子電路中，很少使用邏輯門，而在其他一些電路中，微處理器包括數(shù)百萬個(gè)邏輯門。TheimplementationofLogicgatescanbedonethroughdiodes,transistors,relays,molecules,andopticsotherwisedifferentmechanicalelements.Forthisreason，basiclogicgatesareusedlikeelectroniccircuits.邏輯門可以通過二極管、晶體管、繼電器、分子和光學(xué)或其他不同的機(jī)械元件來實(shí)現(xiàn)。因此，基本邏輯門就像電子電路一樣使用。Therearesomanyapplicationsofbasiclogicgates,howevertheymostlydependontheirtruthtablesotherwiseformsofoperations.Basiclogicgatesarefrequentlyusedincircuitssuchasalockwithpush-button,thewateringsystemautomatically,burglaralarmactivatedthroughlight,safetythermostat&othertypesofelectronicdevices.基本邏輯門的應(yīng)用如此之多，然而它們大多依賴于它們的真值表或其他形式的運(yùn)算?；具壿嬮T經(jīng)常用于電路中，例如帶按鈕的鎖、自動(dòng)澆水系統(tǒng)、通過燈光激活的防盜警報(bào)器、安全恒溫器和其他類型的電子設(shè)備。Themainadvantageofbasiclogicgatesisthattheycanbeusedinadifferentcombinationalcircuit.Byusingmixturesofbasiclogicgates,advancedoperationsareoftenperformed.Intheory,there’snolimittothenumberofgatesthatmaybecoveredinadevice.However,intheapplication,there’salimittothenumberofgatesthatmaybepackedintoagivenphysicalarea.AsICtechnologyadvances,thedesiredphysicalvolumeforeveryindividualgatedecreases,anddigitaldevicesofanequivalentorsmallersizebecomecapableofactingwithmorecomplicatedoperationsatev