電子信息科學與技術專業(yè)外文翻譯-單片機基礎知識-全文預覽
【正文】 us t be use d to e ns ur e the ma xi mu m c lo c k fre q ue nc y is a ppr oa c he d b ut no t e xc ee ded . Ma ny clo c k cir c ui ts a lso w or k w i th a r esis tor a nd c ap aci tor a s l ow c os t ti mi ng c o mp o ne nts or ca n be dri ve n fr o m a n e xter nal so urc e. T his la tter a rra nge me nt is use ful is e xter nal s ync hr o ni za ti o n o f the mi c r o c o mp ute r i s r e q ui r ed . 。 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. Random access memory (RAM). R A M is for the s tora ge o f w or ki ng vari able s a nd d a ta us ed d uri ng p ro gra m e xec utio n. T he si ze o f thi s me mo r y varie s w i th d evi ce typ e b ut i t has the sa me c har ac teris ti c w i d th (4 ,8 ,1 6 bi ts e tc.) as the p ro cess or , Sp eci al func tio n re gis te rs, s uc h as s ta c k poi nter o r ti me r r e gis ter ar e o fte n lo gic all y i ncor po ra te d i nto the R A M a rea . It is als o c o mmo n i n Ha rar d type micr oc o mp uter s to tre a t the R A M ar ea as a c olle c tio n o f r e gis ter 。 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 n
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