Chuong 14_Ghep Noi Bo Nho Ngoai - Smith.N Studio

8/2/2019 Chuong 14_Ghep Noi Bo Nho Ngoai - Smith.N Studio

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Ch-ng 14Phi php 8031/51 vi b nh ngoi

14.1 B nh bn dn.Trong phn ny ta nh v cc kiu loi b nh bn dn khc nhau v cc c

tnh ca chng nh- dng l-ng, t chc v thi gian truy cp. Trong thit k ca ttc cc h thng da trn b vi s l th cc b nh bn dn -c dng nh- hi l-u

gi ch-ng trnh v d liu chnh. Cc b nh bn dn -c ni trc tip vi CPU vchng l b nh m CPU u tin hi v thng tin ch-ng trnh v d liu. V l dony m cc b nh nhiu khi -c coi nh- l n phi p ng nhanh cho CPU mcc iu ny ch c cc b nh bn dn mi c th lm -c. Cc b nh bn dn-c s dng rng ri nht l ROM v RAM. Tr-c khi i vo bn cc kiu b nhROM v RAM chng ta lm quen vi mt s thut ng quan trng chung cho tt cmi b nh bn dn nh- l dung l-ng, t chc v tc .14.1.1 Dung l-ng nh.

S l-ng cc bt m mt chp nh bn dn c th l-u -c gi l dung l-ngca chp, n c n v c th l kilbt (Kbt), mgabit (Mbt) v.v iu nyphi phn bit vi dung l-ng l-u tr ca h thng my tnh. Trong khi dung l-ngnh ca mt IC nh lun -c tnh theo bt, cn dung l-ng nh ca mt h thngmy tnh lun -c cho tnh byte. Chng hn, trn tp ch k thut c mt bi boni rng chp 16M tr nn ph dng th mc d n khng ni rng 16M ngha l16 mgabit th n vn -c hiu l bi bo ni v chp IC nh. Tuy nhin, nu mtqung co ni rng mt my tnh vi b nh 16M v n ang ni v h thng mytnh nn n -c hiu 16M c ngha l 16 mgabyte.14.1.2 T chc b nh.

Cc chp -c t chc vo mt s ngn nh bn trong mch tch hp IC. Mingn nh c cha b bt, 4 bt, 8 bt thm ch n 16 bt ph thuc vo cch n -cthit k bn trong nh- th no? S bt m mi ngn nh bn trong chp nh c th

cha -c lun bng s chn d liu trn chp. Vy c bao nhiu ngn nh bntrong mt chp nh? N ph thuc vo s chn a ch, s ngn nh bn trong mtIC nh lun bng 2 lu tha vi s chn a ch. Do vy, tng s bt m IC nh cth l-u tr l bng s ngn nh nhn vi bt d liu trn mi ngn nh. C th tmtt li nh- sau:1. Mt chp nh c th cha 2x ngn nh, vi x l s chn a ch.2. Mi ngn nh cha y bt vi y l s chn d liu trn chp.3. Ton b chp cha (2x y)bt vi x l s chn a ch v y l s chn d liu trn

chp.14.1.3 Tc .

Mt trong nhng c tnh quan trng nht ca chp nh l tc truy cp dliu ca n. truy cp d liu th a ch phi c cc chn a cha, chn cREAD -c tch cc v sau mt khong thi gian th d liu sxut hin cc chnd liu. Khong thi gian ny cng ngn cng tt v tt nhin l chp nh cng t.Tc ca chp nh th-ng -c coi nh- l thi gian truy cp ca n. Thi gian truycp ca cc chp nh thay i tvi nangiy n hng trm nangiy ph thucvo cng ngh s dng trong qu trnh thit k v sn xut IC.

C ba c tnh quan trng ca b nh l dung l-ng nh, t chc b nh vthi gian truy cp s -c s dng nhiu trong ch-ng trnh. Bng 14.1 nh- mt

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tham chiu tnh ton cc c tnh ca b nh. Cc v d 14.1 v 14.2 s minh honhng khi nim va trnh by.

Bng 14.1:Dung l-ng b nh vi s chn ac ch ca IC.

x 10 11 12 13 14 15 16 17 18 19 20 21 22 23 242x 1K 2K 4K 8K 16

K

32

K

64

K

12

8K

25

6K

51

2K

1

M

2

M

4

M

8

M

16

M

V d 14.1:Mt chp nh c 12 chn a ch v 4 chn d liu. Hy tm t chc b nh v

dung l-ng nh ca n.Li gii:a) Chp nh ny c 4096 ngn nh (212= 4096) v mi ngn nh cha 4 bt d liu

nn t chc nh ca n l 4096 4 v th-ng -c biu din l 4K 4.b) Dung l-ng nh ca chp nh l 16K v c 4 K ngn nh v mi ngn nh c 4

bt d liu.

V d 14.2:Mt chp nh512k c 8 chn d liu. Hy tm a) t chc ca n v b) s chna ch ca chp ny.Li gii:a) Mt chp c 8 chn d liu c ngha l mi ngn nh c 8 bt d liu. S ngn

nh trn chp ny bng dung l-ng nh chia cho s chn d liu =512k/8 = 64.Do vy t chc nh ca chp l 64k 8.

b) S -ng a ch ca chp s l 16 v 116= 64k.14.1.4 B nh ROM.B nh ROM l b nh ch c (Read only Memory). y l mt kiu b

nh m khng mt cc ni dung ca n khi tt ngun. Vi l do ny m b nh

ROM cn -c gi l b nh khng bay hi, c nhiu loi b nh ROM khc nhaunh-: PROM, EPROM, EEPROM, EPROM nhanh (flash) v ROM che.14.1.4.1 B nh PROM.B nh PROM l b nh ROM c th lp trnh -c. y l loi b nh m

ng-i dng c th t ghi thng tin vo. hay ni cch khc, PROM l b nh ng-idng c th lp trnh -c. i vi mi bt ca PROM c mt cu ch. B nhPROM -c lp trnh bng cch lm t nhng cu tr. Nu thng tin -c t votrong PROM m sau th phi b v cc cu tr ca n bn trong b t vnh vin vil do ny m PROM m -c gi l b nh ROM lp trnh mt ln. Vic lp trnhROM cng -c gi l t ROM v n i hi phi c mt thit b c bit gi l b

t ROM hay cn gi l thit b lp trnh ROM.14.1.4.2 B nh EPROM v UV EPROM.B nhEPROM -c pht minh ra cho php thc hin thay i ni dung

ca PROM sau khi n -c t. Trong b nhEPROM ta c th lp trnh chpnh v xo n hng nghn ln. iu ny l c bit cn thit trong qu trnh phttrin mu th ca mt d n da trn b vi x l. Mt EPR s dng rng ri -cgi l UV EPROM (UV l ch vit tt ca tia cc tm Ultra Violet). Vn tnti duy nht ca UV EPROM l thi gian xo ca n qu lu (20 pht).



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Tt c cc chp nh UV EPROM c mt ca s -c dng chiu tia bcx cc tm xo cc ni dung ca n. Vi l do ny m EPROM cng cn -c coinh- l b nhEPROM -c xo bng tia cc tm hay n gin -c gi l UV EPROM. Hnh 14.1 trnh by cc chn ca mt chp UV EPROM.

lp trnh cho mt UV EPROM cn thc hin cc b-c.1. Xo cc ni dung ca n, xo mt chp th phi tho n ra khi cm trn

bng mch h thng v t n vo thit b xo EPROM chiu x tia cc tmkhong 15 20 pht.2. Lp trnh cho chp. lp trnh cho mt chp UV EPROM th t n vo thit

b t (thit b lp trnh ). t ch-ng trnh v d liu vo EPROM th thit bt ROM s dng in p 12.5V hoc cao hn ph thuc vo loi EPROM. inp ny -c gi l Vpp trong bng d liu ca UV EPROM.3. Lp chp nh tr li cm trn h thng.

T cc b-c trn y ta thy cng nh- cc thit b t EPROM th cng ccc thit b xo EPROM khc nhau. V tt c cc kiu b nh UVEPROM u cmt nh-c im chnh l khng th -c lp trnh trc tip trn bng mch ca hthng. Do vy, b nhEPROM -c ra i gii quyt vn ny.

Hy n cc k hiu m s ca cc IC trong bng 14.2. v d, m s bphn 27128 25 dnh cho UV EPROM c dung l-n v thi gian truy cp l250ns. Dung l-ng ca chp nh -c k hiu trn m s b phn (part number) vthi gian truy cp -c b i mt s0. Trong cc m s b phn th ch C l cngngh CMOS, cn 27xx lun ch cc chp nhEPROM. bit thm chi tit ta vomc s tay cc chp nh ca cc hng chng hn JAMECO (jameco.com) hay JDR(jdr.com) theo -ng mng internet.

Bng 14.2: Mt s chp nh UV EPROM.

HNH 14.1Hnh 14.1:B tr cc chn ca h cc chp nh ROM 27xx.

V d 14.3:i vi ROM c m b phn l 27128 c dung l-ng nh l 128k bt. Tra

bng ta thy t chc ca n l 16k 8 (tt c mi ROM u c 8 chn d liu) iuny ni ln rng n c 8 chn d liu v s chn a ch -c tm thy l 14 v 214=16k.14.1.4.3 B nh PROM c th xo -c bng in EEPROM.B nhEEPROM c mt s -u im so vi EPROM l do v -c xo bng

in nn qu trnh xo rt nhanh, nhanh rt nhiu so vi thi gian xo 20 pht ca

UEPROM. Ngoi ra trong EEPROM ta phi xo ton b ni dung ca ROM. Tuynhin, -u im chnh ca EEPROM l ta c th lp trnh v xo khi chp nh vn trn gi cm ca bng mch h thng m khng phi ly ra nh- i vi UV EPROM. Hay ni cch khc l EPROM khng cn thit b lp trnh v thit b xongoi nh- i vi UV EPROM. hon ton to thun li cho EPROM nh thitk phi kt hp vo bng mch ca h thng c mch in lp trnh EEPROM sdng in p Vpp =5V nh-ng chng rt t. nhn chung, gi thnh cho 1 bt caEEPROM t hn rt nhiu so vi UV EPROM.



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Bng 14.3: Mt s chp EEPROM v chp nhFlash (nhanh).

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Chuong 14_Ghep Noi Bo Nho Ngoai - Smith.N Studio