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第 4 章 组合逻辑电路 PowerPoint PPT Presentation


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《 数字电子技术基础 》. 第 4 章 组合逻辑电路. 数字电路可以分成两大类: 组合逻辑电路和时序逻辑电路。 组合逻辑电路的分析方法和设计方法 常用中规模组合逻辑电路的结构和原理 应用中规模集成芯片的设计方法 组合逻辑电路竞争 - 冒险现象的成因,以及消除竞争 - 冒险现象的常用方法。. 4.1 组合逻辑电路的分析方法. 1 .组合逻辑电路的结构特点 组合逻辑电路是由各种门电路组成的,用于实现复杂的组合逻辑功能。 组合逻辑电路的特点:组合电路的输出信号仅取决于同一时刻的输入信号,与电路原来所处的状态无关。

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第 4 章 组合逻辑电路

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4

4

--


4

4.1

  • 1

  • x1, x2, , xmy1y2,yn

y1 = f1(x1, x2, , xm)

y2 = f2(x1, x2, , xm)

yn = fn(x1, x2, , xm)


4

2

  • 1

  • 2

  • 3

  • 4


4

  • 4.1

  • 1

  • 2

  • 3Y = AB


4

  • 4.2

  • 1

  • 2

  • 3

  • 4


4

4.2

  • 4.2.1

  • Encoder


4 2 2

4.2.2

  • Decoder

  • 1

  • nNN=2nN<2n

  • 12-4

  • 74139 =0

2-4

= 1 0

1


4

23-874138

  • 74138383-8

  • 38

  • GSS=1

  • A2A1A0S1

  • S1=1 GSS=1


4

  • GSS=0

  • GS

3 -- 8


4

  • 4.4 4741381741395-32

  • 4741383A2A1A053D2D1D0

  • 74138S1 13

  • D4D374139474138


4

2-

  • 8421BCD1010

  • 8421BCD10101111


4

3

  • 74138

  • S1EN A2A1A0

  • EN=1DA2A1A0

  • EN=1 A2A1A0=101D


4

  • 4

  • 8421BCD

  • 7448


4

  • 7448

  • A3A0BCDYaYg7

  • Yi=1Yi=0


4

  • 7448

  • 7448

  • /

  • =0YaYg=1

  • =1


4

  • =0

  • 539.7039.70

  • =0A3A0=0000YaYg00A3A0000010.0

  • /

  • / =0A3A0

  • =0 0


4 2 3

4.2.3

  • 141

  • 74LS15341

  • 41A1A0

  • 41

  • =0

  • =1

  • 41


4

  • 4.5 4181

  • 813A2

  • A2

  • A2=0D0D3Y1Y2

  • A2=1D4D7Y2Y1

    81

  • 8174151


4

  • 81

  • 4.681321

  • 321325474151141

  • A4A341474151


4 2 4

4.2.4

  • 1

  • AB

YA=B = AB


4

2

  • A3A2A1A0=1000B3B2B1B0=0111A3>B3A>BA3=B3A2B2

  • 74LS85

I(A>B)I(A<B) I(A=B)


4

  • 4.774LS85

  • 21412

  • I(A>B)I(A<B)0I(A=B)1

  • I(A=B)18Y(C=D)1


4 2 5

4.2.5

  • 1

  • ABSCO

CO=AB


4

2

  • ABCISCO

  • CO

S = ABCI

CO = (AB) CI+AB

A=1011 B=1110

1 0 1 1 A

1 1 1 0 B

+) 1 1 1 Ci

1 1 0 0 1 A+B


4

3

  • 74LS283

Y0= (CI)0

S0= A0B0CI

Y2 = A1B1+(A1+B1) A0B0+(A1+B1) (A0+B0)CI = (CI)2

Y3 = A2B2+(A2+B2) A1B1+(A2+B2) (A1+B1) A0B0+(A2+B2) (A1+B1) (A0+B0)CI = (CI)3

Si = AiBiCIi


4

  • YIAi-1Bi-11Ai-1Bi-11Ai-2Bi-2

  • (CI)iAiBi(CI)i

  • 74LS2834

  • 74LS283812


4

4.3

  • 110

  • 2

  • 3

  • 4

  • 5


4 3 1

4.3.1

  • --

  • 4.8

  • 1RAG10YY0Y1

  • 2


4

  • 30Y

  • 40YY

  • 51YY

  • 6


4

  • 4.9

  • i3AiBiCi-1DiCo

  • 1ABCICOD

  • 2

  • 3

  • 4


4 3 2

4.3.2

  • 4.10

    3-8874138S1=1 74138

  • ABC74138


4

4.11

  • 1817415174151 =074151

  • ABCS2S1S0

  • D0=D2=DD1=D4=1D3=D6=

  • 0

  • 818

  • 8S2S1S0000111YD0D7


4

4.12

  • 74283

  • ABB1B74283CI1B+1B

  • ABCO=1

  • A<BCO=0

  • 1ABA+B+11CO=101S3S2S1S02ABD3D2D1D01CO=011S3S2S1S0 2S3S2S1S0 +1ABD3D2D1D0

  • A=9B=10AB11001+0101+1=011111CO=020001

  • A=12B=1011100+0101+1=100101CO=1

  • 20010


4

  • 4.13 418421BCD

  • 48421

  • 6+7=138421BCD11018421BCD61001113

  • 8+9=178421BCD1000161011117

  • 6

  • 1015

  • CO6

7428318421BCD12B3B2B1B06Y12A3A2A1A0 = 01106Y02A3A2A1A0 = 00002S3S2S1S0Y


4

4.4

  • 4.4.1

  • A01 10 0BA1tpd1

  • BA1tpd0


4

  • B=C=1

  • A A1tpd AC1tpdY


4 4 2

4.4.2

  • 1

  • BC B=C=1Y=1BC

  • 2

  • A=C=0

  • A=C=0Y=0

  • 3

  • 4 420 pF


4

4.3

Y(A,B,C,D)=m(0,2,4,6,8,9,10,13,14)

4.53ABCBACY1Y2


4

  • 4.10 4.44814174153Y

  • 4.12 3-874LS138

    1 2

    3


4

  • 4.13 4-1674LS1544.4574LS154A3A0Y15Y0

  • 1

  • 2

  • Y1=m(2,3,4,7,12,13,15)

  • Y2=m(0,1,5,6,9,11,14)

  • 4.14 41 74LS153

    1 Y1=m(0,1,2,6,5,7)

    2Y2 =m(0,2,5,7,8,10,13,15)

    3 Y3=m(1,6,7)


4

  • 4.19 81YABCD4.47


4

4.21 3-8

  • Y0Y7

  • A7A0

  • A7A6A5A4A3A2A1A0

  • 11100 000 - 11100 111

  • ( E0 E7 )H

    4.22 47485474283

  • YA>B=1, A-B A+B+1

  • YA>B=0, B-A B+A+1


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