4.16 试在图4.2.31的基础上增加一片7485,构成25位数据比较器。
解:
4.17 设A=A
3
A
2
A
1
A
0
,B=B
3
B
2
B
1
B
0
均为8421BCD码。试用74283设计一个A、B的求和电路。
(可用附加器件)
解:设CO S
3
S
2
S
1
S
0
为A、B的二进制和,则当CO=1或S
3
S
2
S
1
S
0
>1001时,须加0110修正项进行
调整,计算结果为C
4
C
3
C
2
C
1
C
0
。
4.18 用74283将8421BCD码转换为余3BCD码。
解:电路图如右所示:
4.20 用74283将8421BCD码转换为5421BCD码。
解:
Page 13 of 61
1 2 3 4 5 6
A
B
C
D
654321
D
C
B
A
Title
Number RevisionSize
B
Date: 5-Mar-2002 Sheet of
File: E:\Design Explorer 99 SE\Library\YangHengXin\MyDesign.ddbDrawn By:
S
B
B
B
1
2
0
1
74283
A
A
A
3
A
S
S
0
2
1
B
2
3
0
3
S
CO
CI
0
0
0
1
1
8421BCD
Óà 3 B C D
=
A
3
A
2
A
1
A
0
B
3
B
2
B
1
B
0
(A>B)
i
(A=B)
i
7485
(A<B)
i
F
A>B
F
A=B
F
A<B
A
20
B
20
A
24
A
23
A
22
A
21
B
24
B
23
B
22
B
21
=
A
3
A
2
A
1
A
0
B
3
B
2
B
1
B
0
(A>B)
i
(A=B)
i
7485
(A<B)
i
F
A>B
F
A=B
F
A<B
A
5
B
5
A
9
A
8
A
7
A
6
B
9
B
8
B
7
B
6
A
3
A
2
A
1
A
0
B
3
B
2
B
1
B
0
(A>B)
i
(A=B)
i
7485
(A<B)
i
F
A>B
F
A=B
F
A<B
0
=
A
3
A
2
A
1
A
0
B
3
B
2
B
1
B
0
(A>B)
i
(A=B)
i
7485
(A<B)
i
F
A>B
F
A=B
F
A<B
A
0
B
0
A
4
A
3
A
2
A
1
B
4
B
3
B
2
B
1
=
A
3
A
2
A
1
A
0
B
3
B
2
B
1
B
0
(A>B)
i
(A=B)
i
7485
(A<B)
i
F
A>B
F
A=B
F
A<B
A
10
B
10
A
14
A
13
A
12
A
11
B
14
B
13
B
12
B
11
=
A
3
A
2
A
1
A
0
B
3
B
2
B
1
B
0
(A>B)
i
(A=B)
i
7485
(A<B)
i
F
A>B
F
A=B
F
A<B
A
15
B
15
A
19
A
18
A
17
A
16
B
19
B
18
B
17
B
16
F
A>B
F
A=B
F
A<B
A
3
A
2
A
1
CO
A
0
S
3
CI 74283 S
2
B
3
S
1
B
2
S
0
B
1
B
0
A
3
A
2
A
1
A
0
B
3
B
2
B
1
B
0
1
A
3
A
2
A
1
CO
A
0
S
3
CI 74283 S
2
B
3
S
1
B
2
S
0
B
1
B
0
S
3
S
2
S
1
S
0
0
0
C
4
C
3
C
2
C
1
C
0
1 2 3 4 5 6
A
B
C
D
654321
D
C
B
A
Title
Number RevisionSize
B
Date: 5-Mar-2002 Sheet of
File: E:\Design Explorer 99 SE\Library\YangHengXin\MyDesign.ddbDrawn By:
S
B
B
B
1
2
0
1
74283
A
A
A
3
A
S
S
0
2
1
B
2
3
0
3
S
CO
CI
0
0
0
1
1
8 4 2 1 B C D
Ó à 3 B C D
1 2 3 4 5 6
A
B
C
D
654321
D
C
B
A
Title
Number RevisionSize
B
Date: 19-Feb-2002 Sheet of
File: C:\Program Files\Design Explorer 99 SE\Library\YangHengXin\MyDesign.ddbDrawn By:
F
(A=B)
B
B
B
1
2
0
1
i
i
(A<B)
7485
(A>B)
A
A
A
3
i
A
F
F
A>B
A<B
A=B
B
2
3
0
1 2 3 4 5 6
A
B
C
D
654321
D
C
B
A
Title
Number RevisionSize
B
Date: 5-Mar-2002 Sheet of
File: E:\Design Explorer 99 SE\Library\YangHengXin\MyDesign.ddbDrawn By:
S
B
B
B
1
2
0
1
74283
A
A
A
3
A
S
S
0
2
1
B
2
3
0
3
S
CO
CI
0
0
0
1
1
8 4 2 1 B C D
Ó à 3 B C D
1 2 3 4 5 6
A
B
C
D
654321
D
C
B
A
Title
Number RevisionSize
B
Date: 19-Feb-2002 Sheet of
File: C:\Program Files\Design Explorer 99 SE\Library\YangHengXin\MyDesign.ddbDrawn By:
F
(A=B)
B
B
B
1
2
0
1
i
i
(A<B)
7485
(A>B)
A
A
A
3
i
A
F
F
A>B
A<B
A=B
B
2
3
0