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- Chương 3: Khèi ®Õm
*Bé ®Õm thuËn 10:
B¶ng tr¹ng th¸i:
t t+1
Qd Qc Qb Qd Qc Qb
Qa Qa
0 0 0 0 0 0
0 1
0 0 0 0 0 1
1 0
0 0 1 0 0 1
0 1
0 0 1 0 1 0
1 0
0 1 0 0 1 0
0 1
0 1 0 0 1 1
1 0
0 1 1 0 1 1
0 1
0 1 1 1 0 0
1 0
1 0 0 1 0 0
0 1
1 0 0 0 0 0
1 0
+ThiÕt kÕ,chän c¸c phÇn tö m¹ch: 4 phÇn tö nhí JK-FF vµ c¸c phÇn tö
logic tæ hîp.
+2 ph-¬ng ph¸p thiÕt kÕ bé ®Õm: ThiÕt kÕ ®ång bé hî¨c kh«ng ®ång
bé.
a.1>ThiÕt kÕ ®ång bé:
- LËp b¶ng m· hãa theo b×a Karough,b¶ng kÝch,tõ ®ã ta t×m ®-îc hÖ ph-¬ng
tr×nh kÝch:
J1=QcQbQa
K1=Qa
J2=K2=QbQa
J3= Qd Qa
K3=Qa
J4=K4=1
S¬ ®å m¹ch:
a.2>ThiÕt kÕ kh«ng ®ång bé:
Tõ hÖ ph-¬ng tr×nh kÝch m¹ch ®Õm ®ång bé ta cã:
J1=QcQb ; K1=1 ; Xung nhÞp Ck1=Qa
J2=K2=Qa ; Ck2=Qb
J3= Qd ; K3=1 ; Ck3=Qa
J4=K4=1 ; Ck4= Xung ®Õm.
S¬ ®å m¹ch:
- *KL: Thùc tÕ m¹ch ®Õm 10(®Õm thuËn) dïng lµ IC ®Õm: 7490/74LS90
- b>Khèi gi¶i m·:
*M¹ch gi¶i m· BCD 4 bit ra m· 7 thanh:
Víi LED 7 thanh:
B¶ng tr¹ng th¸i ho¹t ®éng m¹ch gi¶i m·:
Chữ ABCD a b c d e
số f g
0 0 0 0 0 1 1 1 1 1
1 0 0 0 1 1 0
2 0 0 1 0 0 1 1 0 0
3 0 0 1 1 0 0
4 0 1 0 0 1 1 0 1 1
5 0 1 0 1 0 1
6 0 1 1 0 1 1 1 1 0
7 0 1 1 1 0 1
8 1 0 0 0 0 1 1 0 0
- 9 1 0 0 1 1 1
1 0 1 1 0
1 1
1 0 1 1 1
1 1
1 1 1 0 0
0 0
1 1 1 1 1
1 1
1 1 1 0 0
1 1
ThiÕt kÕ m¹ch dïng c¸c phÇn tö logic tæ hîp:
a = C + A + B D +DB
b = A +B
c = A+ C +B+D
d = C + A +D + B D
e = CD +B D
f = A + C D + B D + BC
g = C D + B D +B C + B
*KL: Thùc tÕ dïng IC gi¶i m·: 7447/74LS47
- 74LS90,74LS47,LED Anot chung.
SN7490(7490),SN7447(7447),LED Katot chung.
nguon tai.lieu . vn
