I, R2=LR 4, Nhu v~y mQt cau can bang la cau co:
b) II¢ thO"ng truyin thOng da die'm
Rinh 2.74. Cae h¢ thOng truyin thOnR.
Neu truyen thong thlfc hi¢n giua hai thiet b~ thi gQi do la ket noi di~m- tai ditim (point-to-point. Trang h¢ thong co di¢n tir thutmg co yeu cau mOt h¢ thong chi] (master) ket noi vai nhieu
M
thong con. Trang tflfang hQ'p nay. neu sip xep di~m -tai di6m. h¢ thong chi] se pMi ket noi tai tUng h¢ thong can riengIe.
lhinh 2.74a). tue c6 cae c6ng va duoog truyent th6ng rieng cho tung h~t thong can.
Ket
noi cling co the bo tri thea each da di6m (multi-point), & do tatd
cae thiet bj dU(Je noi voi m¢t dUCmg truyen (hinh 2.74b). Nhfrng n3m gan day kythu~1t m~ng rL¢i b¢ (LAN) cho phep thl!e hi~n truyen dfr li¢u nhanh ho'n. nhicu so voi hai giai phap truyen diem-di~m neu trcn.
Giiia cac may linh, dii li~u thuang truycn thea dl((]l/?, sOllg sOl/g. Oic buyt (bus) dii li¢u song sang truyen 8,16 ha~c 32 bit dong thai, vai moi buyt rieng Ie truyen mc)t bit dii li¢u
va
cae tin hi¢u dieu khien. Truyen du li~u sang song eho toc dQ truycn nhanh nhlffig chi phi caa VI dbi hoi co m<;lch giao di¢nva
cap. LO'.li truyen du li~u song song hay duqc dung de truyen gan co yeu cau toe dQ truyen cao.Tru)lfl dii' li¢u nt/i ti{p: dfr li~u cung vai eac tin hi¢u dieu khien dU'qc truycn tuan tl,f bit sau bit dQc thea m¢t dU'Ong truyen do'n., co the thea:
1. H¢ drm con?,: truyen chi thlJc hi¢n thea mQt phuang,
tu
thiet bi A tai thiet biB,
kh6ng e6khii
nang truycn nglIqc l~i (vi d\l, may tinh truyen du li¢utai
may in).
2. H¢ ban kip: trang do du li~u truyen thea m9t hUCmg t~i mQt thai diem, e6 the thay d6i huang. Ok thiet bi cuo; tiiii cae mut lien ket c6 the dao chicu til truyen sang nh~n (nhlfng kh6ng tiiii cung ml)t thai diem).
3. H¢ kep: trang do du 1i¢u co the duqc truyen dong thoi thea ca hai hl1Cmg gifra thiet bi A va B.
Trang truyen noi tiep, thiet bi nh~n dn biet ncri m¢t kf tt! bat dau
va
dimg. Truyen c6 the la dong hQ ho~c khan!!, dCingbr.
+ Truye'n kh6ng dong b¢: thict bi nMn va gili ha~t d¢ng khong dong thai, moi thiet bi co tin hi~u dong ho dOc l~p. Thoi gian gifra cae kf tt! duqc truyen 1a
tuy ti¢n. M6i ki tl,f truyen d9c thea dlICmg ket no; duqc moi bCri. hit xuiit pM! (start bit)
dC'
baa eho may nh~n slJ xuat phat eua ki tl!, tiep thea Iii hit d/eng (stop. ~j
I .__ .J_. __ LJ_J __ . __
, • , , ,L __
,LLJ,
, II : : : : : : , : I
Cae d,,!m 11y ma"
I(twng
j : : . : ' ,
~ ____ . ..! _____ ~ _____ ..! _____ ..!. ____ ..! ______ + _ _ _ _ _ _ • _ L - - - - _. _. __ """ i'.''-' 1"'-' I'.>u ILL" 0", p,," I",,, "
..
, "_." """ i'.''-' 1"'-' I'.>u ILL" 0", p,," I",,, "..
, "_."1\,' "" " !I" , II" ~ B" \ 1<" .j n" , 11,\ " ., , "., II"
thai thanh ghi Jong cli?n va nhay tai m¢1 vi trf b¢ nha da dUQ'c xac dinh boi phan cung h(l$c bt'!i ph,i.n m~m I~p bCii nguo-i
Slr
dl.lng. M(ll thu tL,le (routine) dUQ'e thlfchi~n t';li
vt
tri nay. Thil t!,lc nay clllQ'C gQi la thrl tl.IC plll.IC VI} IIgat (interupt service rounlinc).3. 1 ruy qip trw·
tiel)
b(J 111/(1 (direct memory access -DMA) la lo<.tl truycnlfl!C tlCP diJ lj~u tiI bQ nha den cae thiet b~ ngo<;1i
vi,
nhu d.c b¢ clieu khien dla cU'ug,cae
b¢ dieu hQ'p m<;tng va cae thiel bi ghi dlf phung vao bang tiI (chCr kh6ng phai giua may tfnh vai may tfnh). Cac yeu cau truyen dO' li~u deu dugc quanIy
bOi rIl(?t chip d~c bi?t, g9i Iii. chip dieu khien DMA ( DMA controller). hO';lt d(mg 6 toc dQ cua b¢ vi xu IY.
2.5.2.
M~ngebng hie
M';lng (Illig
tac
li't thu~t ngu dung cho mQt h~ thong cho phep hai ho~e nhieu may tfnh!b¢ xu Ii lien ket de trao doi diJ li¢u. D~ng hQ'p If clla cae ket noi li't m~ng tapo (toIX'Iogy). Thu~t ng[r nut (node) la nai trong m~ng cac m~ch I~p. d.c may dich vl,l t~p va cae thiet bi ngo~i vi dung chung noi voi duo-ng truyen thong (thlfc te nut dong nghla voi tf':lm cong tac). Cac d';lng m';lng truyen thong thuang su dl,lngIa:
I. MQng buyt (bus)
la
m~ng philnquycn, trong d6 m¢t dUCmg noi dun (bus)
hie nao cling cluQ'c tham gia chung bai m¢t s6 cac nut, hinh 2.76(a). M<;1ng buyt thuemg su d!,lng cho cac nut cach nhau hun 100m.
oj
c)
Hinh 2.76. Sap x{p mr;wM dmg hie: 0) m~lIg hl/y!, b) sao, c) phull
