a TENTH EDITION DIGITAL SYSTEMS PRINCIPLES AND APPLICATIONS RONALD J.TOCCI € NEAL S.WIDMER » GREGORY L.MOSS : OUTLINE Numerical Representations Digiral and Analag Systems Digival Vunber Systems Repessenting Bienury Quantities Digiral Ciecuirst.opie Purael asd Serial Transmission Memory Digital Conruters _— ~~ @ OBJECTIVES jpn compevion f this Siaptor, wou will beable ee 1 Distine ish botsuna analog aad cligical representations Gi the advaniages and drawaaeks : digi welatigues compat veil alo, Understund thy nos foraralog-redigiral somvertsrs ‘ADCs and Aigital-aranaley converters MACS Recognire the busie easueteristies of the ainary momher sestem, Cancers a binary rmmbur tis duckinal equivatene, dou ify typical digita signals Idow-afy a tiniay dipran State the diffe-onee# between pavellel end serial cransmission, ncn. {= Distinguish amon: micrecumpnters, mieropracessors, and micrrconerllers @ INTRODUCTION Sn roday’s wos the etm digira? has become pare oi uk every soca Tay bucaue uf Uwe deamatie yay thar digital clreuts and divital teenies Fave becume so rkdely usod in alesrall ates of lifer cumpusers, (oii tion, rohots, mlcul sieves ant rechnology, ransporeadiog,celecomran arian, sates ls.umesl, space explorarinn, and oa ane ou, You ate ali hewi aa exciting educational journey in hich yuu will diseaver the Yura ‘routul princivles, concep, ancl operations U:i¢ans eum (ell digital sestetis, mn the slmplest ania site co Le most consles cartes TE this bouk is suovessfi, yon shonld gain a deep uuderstaclin of hon al tligital sssterus aor, ae yon should Ke able te apply ds lest ‘the analysis anc uoubleshooting of ang digieal system. ‘We start by iuteoducing some inderising concept uu re vie se cf digital technology; these concer will be expanes cn as they are teed “ater in the Look. me also Ineeoduce some o€ te tersinalus «a B necessary whet enibrkang an a nev field of std adl alc this Ts fimpoa tant terms in esery shaprer. ‘tus sana stony Concer 1-1 _ NUMERICAL REPRESENTATIONS Tn seisnve, veeluology, busines, and, in facr, most ather felds of exclu te ane coustin:ly dealing sata quanditis. Quantities are messused, mae lored eeeurded, sanuipulated arithmetically ohaerve, ot in soic ober wey lized in most physical systems, ts inmportan- when dealing with varicus ‘uantities Usst we be uble co tepeesent their yalues efficiently andl ucete rates: There are basically two ways of represencing the numerical value of quantities: analog ad digital Analog Representations In analog representation a quanticy is represented ly a eontannontsly var ble, proportional indicacor, Ad examgleis an autimobile syedometcr irom the ches maecle cays of the 1960 and 197M, The dotlovsion uf the avedle ic proportional to >be speed of the car and follones any evames “ha occur ag the wehiele spesds up oF slows doval, Oa ulder kr, lum le mreehanead ait sunncted the transmission to the speedout eter on thu dush bunts ts Jnteve sting ta mute that cn meteor c4Z8 the aang ewan inn fo small profured evens howgh spoed is now mesouree. ceitally. Theromorerstoforothe digital revo.atiou wed ask ou repacientation £0 masune temperate, ané many ere sull-n use tod. Mercure thermometers tiscri'co amin of mexetay whose height ib prnpoctinal te tum serature, These dlovices are being phased out ofthe dark. lucie uf crvironmeutal con on represcac fiom. Another example fe an outdone seranmeter un which the postion of the pinror rare aretce a ial ae aetal cl egos santas th tem fons, but nonetheless they are an exellent example uf ims prilase changes the pasrion ofthe pointer in peopnttinnal tothe tempor fan. Rewardlens of ho emall the ehange is taser, hers will be proputinnl change in ee indication, Tn thee teu exoamples the physical quantities tj al em sorature} ore Iicing coupled wean indicazor bs pulely mechanical men 14 cloetrieal anslog sesrornythe phvsical quapts that is being means or processed is cotverted to proportional vleage ci cusrout felucts ial signal Mis woltage or eueat js thon used by the system fo clsplay csi, cm eontesl purposes, Sound is an example of a phsical qucaits that ean be resented by an, electrical analog signal, A miecephone ie a device that generates an oonent sallage thet is proportions to the amaplisude af tie sod wars that otk SURaeatuasia (ue areal oe Si teulcdiaee tape re rat va the rane Analog quantitice cach a5 these cited alywe has on important ebazae tovitie, ne macter how tie are sepicsented: hs cam oars cvora sontitues ningeofvaines, The automobile speed ein avs ang wale borcen zet0 and ‘Sy. 100 mph. Siailarly the anferophiowe gua rsight have ny valve within 1 rei of s6n0 ts ID MY (6G, LB, 2.2721 es 9.9000 5 wll produce vatiations in the micropumo%s ordings ean then store sundaes hy wing, the ot 1 the microphone t proportionally changes he rsngnetie cle oot Digital Representations Ju digital representarion the yauntiies are represented net by voutisuously varatde indicators but hy symbnl called its, Asan example, consider the Gig. dock, sich provides the time of day inthe orm of decimal git erat represent ctx and minnres (and semetines seconds Asse knows the rime of dug dhunges continunnsty, not che digital clock readiy davs nt change euitinuuuisly rather. ie changes in steps af ane per minute for per secunud. tn Review aUesTON® the= guns, his digits! representation of the tine of dy cen in oereie Steps, us compared ith rhe represenarion of time poorided by at unslog se Tine-sowcred seal lock: here the dial reading chatyes extinsoush, the majordilfe-ence between analog and digital quantiries chen, can be simply statel as fliows rnalee = eantinians ‘ginal = dliscrere step by step) the diserste natere af digiral rpresuntatins, duro is ny anbigulty ‘whe ring the valve of a cipal quantity, whorwas the value ef a anaes, ‘Quantity is clteu peu to in-eneratien, In practice, when we tke a measure inst of a anulog quar ty, 82 ales puma” a a convient level nf prec ‘on, In uther woud, we digit the quantiy. The dgstal representarior is the Feshir of assigning # nuaber uf Hiited precision to a continuously variable fhuantity Wor exumgle, wien you tee eoor tempetarare witt a mereury (ane log) shermomeser, smercary el unin ussally herwcen to graduation lies, but son noulal pick the nearest Fineard assign ita number uf say. 8661 Which of the following invulee anulox yuuntties aad which Involve digital (01) Tew position switeh {09 Cran Messing fmm on eloctrient antler cs Temporattre uf a oom a} Sand grafss om the beats fe) Automobile fuel suse Solution (0) Digitat (yy Anatow 16) Autor (0) Digiral. since the numker of urains can be vil ver an discrete integer fies and nat very possible value over n cantinnaus ange (e) Amalog.if neo lle =ype: a 11,47 mineral eeadout ax bar giagh dieplay 1-2 DIGITAL AND ANALOG SYSTEMS. A digiol system isa combination of devicos dsigmed tu manipulate Topival informinn ie ses! quaattiee thst ave represented im ligt forme tea 6 che quimiities cas uke only disorece velves, Theses desieee wre mint soften electronic, but thes can also he mecaa veal. magnetic, or prenmatc. Some vf Ue move familia ipsa 3 ice divitelcompurersand cal calatos, digital sudia sud video eawipmors.and the telephone ssstert— he svurleslureest digital systema, ‘An unalog system contains dey-ces that smuuipudute physical quantities thee ure eepnosettod in mali ort, Ja un arse system, die quantities vans vary over 4 vuntiquous eanize uf values. For escmpe, die amplitude of dhe futpel sizuul Lo the speaker 0 radio receiver san have ery value betwee pero and its acicivan init. her eommon avalon systems are audis am pt fies, magnetic tape teverding, amd playback equipment, and a simple light irate switeh Advantages of Digital Techniques Anineveasing majority af applicsrians in elacreaies, aswell asin mest other technologies, nse digital techniques to pestorm operations thar were once herfarited sing analng methods, The chiet Seasons tor the shit ro cgical rechnology are! LL bigient seems are genenaly easter so dest ‘Ihe elves sed in dial ystems are niching erewit, where exact values of vultage or current Are importart, ly rhe range :HIGH pr LGW) in which they fa 2. Injen sionge is ans. "Pri i aceemplished hy spertal davices ane rigeniterhal ean le ota digital jnformarinn and hold it “ar as iene as Fnnpessa ty, and mass storage “echmiczies thar can stare hilian® of bits of Informnator in a relatively small phsieal space. Analng storage ca2ahit: ities ate, hy contrast. excremely imitec seu sid prison ove easier to maintain thraughout te suse. Once ‘a sigual i digitize, ee intormecion ie cortains docs not deteriorate a: ft ti processed. In analeg systems, enc voltage ancl current signals eend co tye distorted by the elfeets of temperature, huunieity, and cem>onent:ol cerunee variations in he elseuite that puocess the sia 4. Opecotion con ho programed. 1 8 Fairly easy to design digital sysrems whose aperat or is enmerclied bya ser of stored instructions called < Jngram. Analng systonrs can alae be pregramet, hue the variety une the complerity cf the wailuble operations are severe lite Digitoscivcnis are less offectat by suis, Spuicios fhuceuatiuas in voltage ike} ae not as critical in digital systems buzause the :xaet value of u ‘ynlge ts not impreane, a Ion atthe nose iv ot lage exoagh to pre ‘yen as from distingnishing m HIGH Frama LOW i. Mian ditto ad on IC chips. Wes ara thar analog Ginerinty has also beneiiied fine the tremendous devalepsvent nf Te technclgs, nt i rlarive cemalexiy and its ise at des cas thar 29101 Iya weenen cally integrated shigh-valve sapacitors precision resistors, inductors. ransformers; have prevented anales swscems from achieving the same high degree of iteration, Limitations of Digital Techniques ‘here are really very few duavbicks when usiag digital techuigues, The two his st priblerse an ‘he real world is analog. Procensinw digitized signals takes Sven 1.2¢bncrmar at Antone See nies 7 ‘Moar physieal quantities ace anal in nature, and these quantities are atten the inputsand outputs that are being monitored, operared an, and coneecled bya system Some examplesre Lengerntnie, pressure, postion, velocity 1s ig evel, flowrate, and so or. We are in dhe lebit of expressing these qua tities distal, such a when we say that dhe Lemperaiare is 66° 153.8" when tye want te he more precise, hut eve ane evally aaahing a divital approsiens tion te au faherent y analog qutatiy Taakeadva tage of d-gital tehiaiques when dala, with analog inputs fn antpurs, Fo aceps must be followed 1. Convert the ahysieal variable to an eleeteieal signal {analog 2, Convert tha aleerrical canaloy) sivnal in. digital fore 2, Protsus:fopetace on the ligieal information. 4. Convert the digiral ourputs buck to realaverld ural, fet An emire sonk contd he writen abuatstep 1 ulute here sre many kins foc dvices thar eomivert various plivsieu taiables icy elec tcl sa, si thls (sensors. These are used eo mesure hing Dt ref ae He” ag wn, On ous ea alot chute ane senses or ad eve as tek, Temparanire iclimare conttol add vane’, welues y smvemdelee),aceelece tian (airbag enllisin dexoetien), pressure filmit wl low rate tonamne just fens To illustrarea typical system eat uses ubis ppvoac Figue FT desertion ‘precision emperagcre regulon system, 8 date posto pw dy us Uorset he desirad temperature m 2° ineceaaets (digit representa) Teinneranins sensn ia ehe heated space cunvurts (is mesure beupeteice toa proportional yleage, Ths aus suliayyeis er ver led tie digital qua Pej hy am analog. te-digial conmerter (ADC) hs value fs ee entpatel 10 the desived welus unt use bo determines i al vale hie mul ea feedea. The digieal value is covert ler sou, qual:ty vel) hy a digiral-reamalog converter (DAC), Ihis wollaps: 8 xiplied tv heating ele wenn sich yl proctce heal tis weld 1p Une el ae all Afect the rv perarine uf the space el Mer i S| Avotier sot] eram ple bere comrerion Weneen ana) aa etl lakes plice isin the "searing nf audio. Comput disks (CDs: have replaced ccissee tapes heeanse chey provide u much butter mous tur recanding a Ccnartnn herr Cases playing back music, Ihe process works semethine like this: (1 sounds fram Ingtruments and buman voiess peod sce au sala ol ane signal ina micro homes (21 this waaine steals exerted La ital foxmral using sn anal {digital conversien process: () the digital inorazation is stored on the CD's surface; (1s dneing plavhack, the CD player takes the digits] Laforastiv Tors the CD snriace and cnnverrs st imo an analoy siwaul that is then aul: Tied and fed 19 sper ker, where it can be picked up by tne human ear ‘Thesecond drawhade to duital stents» hut processiay. hese digitized Ssarala (ste of numbers) takes ae, ad wre also need to convert hetvteen the analog ancl diuitel forms of info.taa tion, which can ald complesity and ‘expanse to a svitem, Lhe ere arecae the ewsmbers need to be the lenge it Takes ro process them. Ln euumy syplica ious, these Lietorsae-outseged hy the nimercis advantagos of using divital teciques, asd so the conversion between analog and oigiral quantities has becume quite eommonpkice in the fue lechnalagy. "There ave sitnarinns, however: where use uf unulux teclniyues is simpler or ime seannmsieal, Far example, several wears auc, a clleaaue (Tut Rohertson) decided to create a conuel system demonstration for tour grup. He planned tosuspord a metallic sbject ina nian Tied as town in Figure 12. eleetremaunet vos made by wir dina cal of wire and can olling the amount of current thr>uzh the eoil. The position ofthe metet ob Jeet was measarec. hy passing an inirarcd Light Vea across (ire myyietie fold. As the abject drew clrser th che mugnutic col, it bexun to block the light eam. Ry measuring small chanzesn the ieht leva, che mano ied could be eontiolied to keep chemetal object hovering and scuiunary, wih 20 Strings atiached. All atremprs ar usta © mieruconpater to measiz> these feety small changes, rin the control calculations said ceive the -aasel [Proved 19 ha toa slot, ever whom usin the fastest, sypst powerful PC aval ablear the rime. His final sclusion uscd just s couple of ¢9amps and a fe dollar? worth nf other evmponents: ull aaa preach Teday we have acease wp processors fast enough ard measurement techaianes precise fneugh ta accomp ish tris feat. hut she simplest solution is still aca, FICURR 1.2 A rasgustic levitation syten singed Plee iconrd ad) tis commu Ls xe buth divs and anatoe teehniques emplosed wii the same sinters w boule la profit from the advantages oF each. In these sired sestens, one of he must icipurlant pas of he design phase invalves : ’ Sremox L2cDust.at Asn ANALG $5.18 9 detenmining whist poets oF the system ave 19 he analog.ard sat parte are 10 Tbe digi, The teen in most systems isa digitize the signal a3 early a3 pos sible and convent it back Uo analog a late as possible as ue siguals flow Throng che sytem, ‘The Future Is Digital ‘he udvunees in digital Leche oey over the gas: three decades hiss heen noting shust af phenomenal, ad there is every rease (a elieve tha more fs coming, Fhiak if the everycae teins that have changed from anal, arinat te liga in your life ime. An inuetosidonr wiseless cizital thermometer fan be purchased for les then $10.03, Cars save gone from having vers Los clecrenic commis to being predomisaatly digitally conuvllod yehicies Digital audio hax muved us co tke eupact disk and AP player. Digital ‘len benughirrhe DVD. Disial home we and still cameras: digital vor ing with systems like Hiv; digial cells a> phones: and dig. tal mang in x ‘ey; magrerie resonance imaging IMI, and ultrasound systems in huspicals ae fuse a few uf eho applications dhut hive beea kaon over by dhe digital revolution. As soon as the infrasiructure is it place, eleplune aiid television, systems will gu digital. he yruvby race in the digital een contiowes tw be Staggering Maybe soar auteniobile is eyuigped with a system such as GMs (6 Star, whic eurns your dashbourd in aul ior wireless eommusivation, {ntomarion, and navigution, You muy aevady be usin vo.ce comands send nr verieve e-mail, call for a traffic report check ex the cur raante- hance needs, © fuse site racio stations er CLs—all sritaeat taking you hands oft the srbeel or sour cyes oil the rad. Cars cunt repost this exact ction in cave of emergency or aicchinict] breslonre, In the coming wears fwivcless communicator will online Uo expand coverage Us provide com nieclivity wherever yuu aie, Telephones will be able to receive, som, and maybe respond Ls ixcoming calls ikea well tained secretary. The digital el esiva revelation will goride nol oaly h.zker detinition of the piel, bat aksousich more flexibility in progiazumiing, Yor will be able tw select the pro frais that yun wn wo view and load them ina yous Lelevisioa’s mae a Tewing sou paiwe ar replay scenes at your convenience, very much lke sieving 4 DVD todus: as vislual reality costinues op ingaose, yuu sil be lable ceimte-uet with the subjvet muller vou ave studing, Tis may nt suttad ‘caelticy when stueving elvetsunies, but imagine shudhing history fram the standpoint of being a participant, @ learning nrapee techniques “ar ery thing. rou athletes to surgery through simulations based on your actus orlor ne, Digit. scalisoluge will eemtinue its high speed incursion inte earrent ar cee af uur Hives well as brea ner oowad in says we ri eer have con Sidered. These uprlitations and many sore} are based om te priseiples ‘prevented in exis tent, Lhe sufimure tools us delet comple systeans-are cut Stantly being upgraded axe avo available ty cayone over the Web, Wesel Study the techuical uuderpinn.nge accessory to communiea e with ey af host (uals ed arene yn fora Faselnaiing sind Fewer, canon oS SS we ‘iu ul zal ecigues over sal? 0 1-3 DIGITAL NUMBER SYSTEMS. ‘Many number systems are in sein digital wednulogy. Ibe most eom-nen are the decimal, hina, oer, and bescadecrnal syecems. Lhe dechna, syste. is Clearly “he ose familiar en ns because i is a tonl that we use evary day. Tramining some of its ckaracreristics will help us to understand che utho: systems berre, Decimal System The decimal system is composed of Lf uummutals or ovate These LD spimbols 06 0,1,2, 3,4, 56,7, 8,95 sng these synbuls as gts oa uber, We EA Cx press any quonrity, The deciral system, al called the haselU system besanse iu¥as TO digits, has evolved natnraly as aresule ofthe faet tha: people have IC Finge:s. Th faethe ward digit ic derived tram the Laitia word aor gor” ‘The decal system is jusiviana-oatue system in vick the valne ot 2 Aligit dleperadson is postion. For exarepls, consider the decal number 455 We kor thar the digie 4 actually represcuts 4 humdeds the 5 reproseuts 5 ‘ang, and tve-} represents tunis, ln coset, thw 4 curries he mos weigh she three digits; iire-erved to. te noustangnofeti dines (SSDI, Khe $a ies the leas weigh ancl is called the Jest mgrakeai dats (25D), Consider another example, 27.95, Unis amber is weavully equal to 2 tes alus F units alus 3 ranths pie hendredths, or 2 4 17 <= 3D + 5 > Gall, The cecimal point is used 10 separate the integer ad frtcriom. risa the number ‘More tignivuy, the varias positions relative 2o the decimal point camry seighterhat can he expressed as 3owers v2 LU, Leas i strate an Lge 1, ‘Shere rhe number 2745214 is represented Lhe decanal pout separates he posit ve powers nt 10 frum tac negative powers, ks number 274.2141 Us fqia to Bw GNI NW ES <u Nw} ay wea sae FIGURE 13 Decines tone ves 8p Dees 1g {i generalany number is simply the sum of the prachers af each digit value ands posit oral value Decimal Counting how counting in the decimal systent, we srt ith 0 in the units pasition and tule cath syinbol (digit) iu progression until we tench §. Then we add a To the asst higher pusition aid start uver sith MF the First pasition fsa