單片機(jī)外文翻譯9-單片機(jī)(編輯修改稿)
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【文章內(nèi)容簡介】 r Program memory Data memory CPU Inputamp。 Output unit memory CPU Inputamp。 Output unit Reset Interrupts Power Fig35A3. Principal features of a microputer Read only memory (ROM). R O M i s us uall y for the p er ma ne nt, no n vol a tile s tor a ge o f a n a ppli ca ti o ns pro gra m . Ma ny mi c ro co mp ute rs a nd micr oc o ntr olle rs a re i nte nde d for hi gh v ol ume a ppli ca ti o ns a nd he nce the ec o no mic al ma nu fa c ture o f the de vice s re q uir es tha t the co nte nts o f the pr o gr a m me mo r y b e co mmi tte d p er ma ne ntl y d uri ng the ma nufa c tur e o f c hi ps . C le arl y, this i mpli es a ri go ro us ap pro ac h to R O M c od e dev elo p me nt si nc e c ha nge s ca nno t be ma de a fter ma nufa c ture . T hi s dev elo p me nt p ro cess ma y i nv olv e e mul a ti o n usi ng a so p his ti ca ted dev elo p me nt s ys te m w i th a hardw a re e mul a tio n cap abil i ty as w ell a s the us e o f p o w e rful s o ftw a re to o l s . S o me ma nufa c turer s pro vid e a ddi tio nal R O M o p tio ns b y i ncl udi ng i n the ir r a nge d evi ces w i th (or i nte nd ed for use w i th) us er p ro gra mma b l e me mo r y. T he si mpl es t o f thes e is us uall y de vic e w hic h c a n o per a te i n a micr opr oc es s or mo d e b y usi ng s o me o f the i np ut/o utp ut li ne s as a n ad dre ss a nd d a ta b us for ac ces si ng e xter nal me mo r y. T hi s type o f devi ce ca n b e ha ve func ti o na ll y as the si ngl e c hip micr oc o mp uter fro m w hi c h i t is deri ve d al bei t w i th res tric te d External Timing ponents System clock Timer/ Counter Serial I/O Prarallel I/O RAM ROM CPU I/ O a nd a mo di fie d e xter nal cir c ui t. T he use o f thes e R O Mle ss d evi ces is co mmo n e v e n i n pr od uc ti o n cir c ui ts w here the v ol ume do es no t j us ti fy the d ev elo p me nt co s ts o f c us to m o n c hip R O M。ther e ca n s till be a si gni fic a nt savi ng i n I/ O a nd o ther c hips co mp ar ed to a c o nve ntio nal mi cr o pro ces sor bas ed c irc ui t. More e xa c t re pla ce me nt fo r R O M de vic es c a n be o b tai ne d i n the fo r m o f v aria nts w i th 39。 pi ggy ba c k39。 EP R O M(Er asa ble pro gr a mma b le R O M )s oc ke ts or d evi ces w i th E P RO M i ns tea d o f R O M 。 T he se de vic es ar e na turall y mo r e e xpe nsi ve tha n eq uiva le nt R O M de vic e, b ut d o pro vi de c o mpl e te circ ui t eq uiv ale nts . E P R O M b ase d de vic es ar e als o e xtre me l y a ttrac ti ve for l ow v ol ume ap plic a tio ns w her e the y pro vi de the a dv a nta ge s o f a si ngle c hi p de vic e, i n ter ms o f o n c hip I/ O , e tc . , w i th the c o nv e ni e nc e o f fl e xi b le us e r p r o gr a mma b i lity.
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