IS), mall I'd gill: (sampled&hel

I, R2=LR 4, Nhu v~y mQt cau can bang la cau co:

d) IS), mall I'd gill: (sampled&hel

tin hi~u wang ttf thanh philn nha, ket qua uua fa m9t ioq.t cac xung h~p, hlnh 2.20 e. 139 trich va gift mau 0), hlnh

2.21, duqc sir dl;lng M giil tUng gia tfj duqc lay mau eho den khi xung tiep thea xuAt hi~n, hinh 20 d. B9 (1) t6ch va giil mau tin hi~u wang ttf, vi~c ehuyen doi thanh tin hi~u so duqc thl,lc hi~n I~i (2)- b9 ehuy~n doi tllang t\\"- s6, hlnh 2. 21.

Moi quan h~ giila vi~c lay mall, diiu vao VA va dau ra ella mQt bQ ehuyen ddi tuang t\\"

-.so

s6 nhj ph{m; 0 va I dU'<)'c g9i

13.

va

bit cao nhit bit thap nhat. Chicu dui cua mQt

tiI (\vord ienght) quyet d~nh d9 ph[m dai cua cau tll, tuc SlJ thay d6i nh6 nh{lt trong V \ se dan den SlI thay doi lrong tin hi~u ra ~o. S\! thay

d6i

so. la

6

vi trl thap nhrlt trang til. Do vay v6i mOt chieu dai tli co /I bit, tOliO thang dau vao tlIdng til

VI'~ se dl1Q"c chia thanh 2n

mau, nhU' v~y st! thay d6i It nha·t d dAu vao c6 tht nh~n d,!-ng dU'Q"c, hie d¢ phan dili cua hi)

chuyen deli dlIQc xac djnh 1£1 Vf.J2". Vi d~,

Vao, T rich &giCl mau Chuyen doi R;;

Tin hieu ttlang 11,1 ⁽¹⁾

~

· 0

.

i

i

~.'lJ

!

I

Till bitu lI.!Oug t\lrn phfl.u s6 cUa gili ![~ FS

lJinh 2.22 . Quan h¢ MIl VOO-1"I1 ('da m(if b(! rIll/yin ddi tur:mg /1/ -sri'

mOt b¢ chuy6n doi wong tl! -s6 c6 chieu dai tiI 1£1 10 bits va tin hi~u wong tl!

a

Thu(\t ngli l}Ufi gial1 cf1l('yi'n

(1tl,.

Nhfrng nguyen If tr~n duqc si'r d~ng trong bQ chuy~n d6i luang t\!- so.

B(i chuyin tIdi /liang tl{-S(/:

Ball vao la tin hi?u tlJong tl! va Mu ra 13. mQt ttl nh~ phan (binary word). B9 chuye'n doi tlJ'dng tt!- s6 co m9t s6 d<}-ng, d~ng thuang dl1Q"c si'r dl:lOg nhai

la

ehuycn d6i tuang tl! -so xap xi k6 tiep. MOt di9n ap duqe sinh boi dong h6 khi rh5.t r:.t day tufln tl! cae xung. Cae xung nay dU<;Ie oem thea kieu s6 nhj phan va III nl1i phall t~o !len dUQ"c chuyen thanh lllQI di¢n ap tUOOg tl! bai hQ chuyen d(~i

Tin hIi~u vaG n.rcrng III

I

~.=:-~I

W

i i i

!

,

Hinh 2.23: Br) chl/y/n d6"i Il((lI1g fl/- -s6',heo xiip xi hell {(It

L S B - - - - ·

Msa

Bitcaol1o.nt Bittb.~[)ul:!at

Hinh 2.24: B(i thl/yin d6'/ sf;'-f/t(fng 11/

M Ihtfl/g fhallg R-2R

sang s6 (DAC). Di¢n rip nay tang thea h<)c va dUQ"C so sanh vai tin hi¢u Woog tl! dau vao til cam bien. Khi di¢n up sinh bai dong ha (clock) VlIqt qua di~n rip Miu vao wem.g tl!, xung tlr dong h6 bi dirng, kh6ng dUQ"e dem tiep do c6ng (gate) dong. Dau ra khoi bi) dem (counter) t;:ti thai diem do bieu dien tin hi¢u so eua di¢n ap tUoog tl!. Thay vi sl! so sanh co the thllC hi¢n bai khoi dau de'm tQ,i I bit thap nhat, rai tiep tye bit thea bit thl phuoog phap xap xi ke tiep eha phep thl!e hi¢n nhanh hon. B¢ chuyen d6i Wem.g tl,l' so xap xi ke tiep tuyen chQn bit cao nhat, nhlffig nha hem. gia tr~ tuem.g tI!, roi b6 sung cae bft nh6 hoo ke tiep, nhlffig toan bi) kh6ng dUQ"c VUqI: qua gia tr~ tuem.g tl!. Vi moi mOt bit cua tiI du\iC thir thea tuan tl!, nen m0t tiI co n hit can n b~c thl!c hi¢n so sanh. Neu dong h6 co t,1.11 so fthl thai gian chuyen doi siS la niL

B(} chuye'n ddi S(j:lll(fllg t~(:

Dau vao hi) chuycn d6i Iii. mQt tli (word), dau ra Iii. tin hi¢u tuang tl!, ia t6ng

cua d.e bits klu)llg zero trong lit. M9t trong nhlrng d~ng ehuyen doi so- tuang tl,l' thuang dUQ"c sir d1,lng la h¢ thong thang R-2R (hlnh 2.24). Di¢n ap dau ra duqc sinh

hoi

ov

B(i (16'11 k('nh (multiplexer): trong

thJ.!c te thuang can thiet thJ.!c hi~n cac phep do

M

VI

Ph~n nh6&

,

Ilinh 2.25: Chuye'll ddi II((ing II/-Mi" sIr d'.lIlg h¢ don kenh

Bq d¢m (huffer) thuang dugc

Slr

tm.

Xlr

11 d~ den ed cau chap hanh ho~e cac thiet bi khac co thi! la qua cMm, do v~y can co b¢ nha ngoai gQi la b9 d¢m

ae

t~m thOi tin hi¢u.

Doi vai phan d¢:m dau vao, dii li¢u duqc truy6n khoi n6 voi toe d9 quyet dinh bbi b9 vi xu If. V 6i phan d¢1l1 dau ra, toc dQ truyeo duge quyet dlnh boi thiet bi dugc cap. B¢ nha d~m dl~n day ho~c trong ding dt bu cho chenh l~ch giila toe d¢ vao b¢ d¢m va toc d9 ra yeu duo Kha naog eua b¢ d¢m phI.). thuQe vao dung tich b¢ nha va chenh l~ch trong toe d¢ truycn dau vao va dau ra.

2.3.2.8.

Dietl

Khi truyen cae tin hi~u DC mvc thap tll cae sensor va dUde xii If b6'i b9 khuech

d,!-i thu~t tmin eo the: xA:y ra hi¢n tLIqng Hinh 2.26: Di/u bie'll bien di} xllnR

troi (drift) tin hi¢u. Van dC nay c6 the tdnh duqc neu thl).'c hi¢n dieu bien, tue truycn tin hi¢u liin lUQ1 (chu kh6ng truyen trl).'e tiep), Caeh truyeo nay con giup

tranh dl1qc giao thoa tin hi¢u. Hinh 2.26 tht hi~n sl! dit'!u bien bien d¢ xung dong

DC

de

a) Bien dq

2.3.3. He thong

thi