III. MACH MA HoA vA GIAr MA
4.1.Den hi~n th~ 7thanh
a
f !sIb
e I Ie
d
a b c d e f g
DLtqc rninh ho~ tn~n hlnh 3.9, rnoi d0<.tn duqe si'r dl,lng m¢t LED ho~e dung tinh th6long. Nhu v~y de dieu khidn den hi~n thi 7 thanh lam vi¢e co 7 dau van ling vOi tUng dO<j.n.
4.2. Bi> giai rna BCD ca 7 thanh
La vi rn<.teh co dau vao I;) rna BCD (4 dau vao), dau ra co 7 dau, dung de e!p tin hi¢u vao bay dau vao tuang dng ella den hi~n thi.
Bang chan ly rna ta ho~t d9ng cila b9 giii rna nhu sau:
DaD vao DaD ra
TT D C B A a b c d e f g 1 0 0 0 0 1 1 1 1 1 1 0 2 0 0 0 1 0 1 1 0 0 0 0 3 0 0 1 0 1 1 0 1 1 0 1 4 0 0 1 I 1 I 1 I 0 0 1 5 0 1 0 0 0 1 1 0 0 I 1 6 0 1 0 1 1 0 I I 0 1 I 7 0 1 I 0 0 0 I I 1 I 1 8 0 1 1 1 I I I 0 0 0 0 9 1 0 0 1 1 1 1 1 I 1 10 1 0 0 1 1 1 I 0 0 1 1
Sa d6 ky hi~u bi? giiti rna BCD ra 7 thanh hinh 3.10, b¢ gioi rna g6rn 4 diiu vao. Oic tin hi¢u vao duqc rna hoa a d~ng rna BCD. Tit 7 dau fa cua be) giai rna duqc n6i toi 7 dati vae luang lIng eua den hi~n thi 7 thanh.
a b c d e f g
D C B A
Ht'nh 3.10: S(fdi} ky hi¢u b¢ gidi rna BCD ra 7thanh
IV. cAe LOM FLIP - FLOP 1. D!nh nghra
Flip - Flop (FF) la philn tir c6 kha nang IUti tril (aM) 1 trong 2 tr~ng thai 0
hay 1. FF co tir 1 den viii dau vae, co 2 dau fa Iuon Iuon nguqc nhau lit Q va Qlliu)'
Sa d6 ky hieu FF nhu hinh 3.11
(P,
Cac - Q
diu
vao dieu Flip -
khitn Flop
Cp -
Q
Hillh 3.1l:Kj hi¢u Flip-Flop
2. Ph an lo~i
C6 nhieu each phan lo~i FE
. Theo chue nang Him vi~c eua cae dau VaG di~u khh~n ta c6 cae lo~i m¢l dau
- Theo each lam vi¢c ta c6 lo~i FF ho~t d¢ng dong h¢ va lo~i ho~t d¢ng khOng dong b¢. (adsbygoogle = window.adsbygoogle || []).push({});
3. Nguyen t~c lam vi~c cua cae lo;:;ti FF
3.1. Lo~; RS FF (H.3.l2)
+ RS FF lo~i kh6ng dong bi).
Hill" 3.12: RS-FF Hogt d(Jng khong d6ng he)
R
s
Khi RS = 00 dau ra Q giG' nguy~n tqng thoU. KhiRS=OI diiuraQ= I Khi RS = 10 dau ra Q = 0 Q RS - FF -Q
Khi RS = 11 kh6ng xac djnh duqc tf<;lng thai dtlu fa ella Q. Vi vi,iy tr~ng thai di~u khi~n nay con duqc gQi ia tqng thai cam.
+ RS FF lo~i dong b¢ (H.3.13): Ho~t d¢ng lUang U! nhu RS FF khOng dong h¢ nhung no chi co tac d~ng dieu khien khi co them xung dua vao.
Q R RS - FF Cp • Q S 3.2. Lo~; D· FF
Doi vo; D.FF ho~t di)ng kh6ng dong bi).
Hinh 3.13: RS-FF Hoqt d¢ng d6ng b¢
Con lo~ d6ng b¢, tfn hi¢u d£lu ra gi6ng tfn hi~u b dau VaG nhtmg bi chiPn di m¢t khoimg thai gian bang m¢l xung nhip.