2010期末考试题A卷

电子科大数电期末考试题

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电子科技大学二零零九至二零一零学年第 二 学

期期

分钟）考试形式：闭卷 考试日期2010年7月12日

课程成绩构成：平时 期中 分， 实验 0 分， 期末 60 分

电子科大数电期末考试题

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一、To fill your answers in the blanks

（1’×25） 1. If [X]10= - 110, then [X]two's-complement=[ 10010010 ]2,

[X]one's-complement=[ 10010001 ]2. (Assumed the number system is 8-bit long)

2. Performing the following number system conversions:

A. [10101100]2=[ 000111010010 ]2421 B.

[1625]10=[ 0100100101011000 ]excess-3

[ 1010011 ]GRAY C.

=[ 10011000 ]8421BCD

D

3. If F (1,2,3,6), then F ( (4. If the parameters of 74LS-series are defined as follows: VOLmax = 0.5 V, VOHmin = 2.7 V, VILmax = 0.8 V, VIHmin = 2.0 V, then the low-state DC noise margin is A,B,C

A,B,C

A,B,C

电子科大数电期末考试题

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high-state DC noise margin is 5. Assigning 0 to Low and 1 to High is called positive logic. A CMOS XOR gate in positive logic is called gate in negative logic.

6. A sequential circuit whose output depends on

the state alone is called a machine.

7. To design a "001010" serial sequence generator by shift registers, the shift register should need bit as least.

8. If we use the simplest state assignment method for 130 sates, then we need at least state variables.

9. One state transition equation is Q*=JQ'+K'Q. If we use D flip-flop to complete the equation, the D input terminal of D flip-flop should be have the 10. Which state in Fig. 1 is ambiguous 11. A CMOS circuit is shown as Fig. 2, its logic

电子科大数电期末考试题

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Fig.1 Fig. 2 12. If number [A]two's-complement =01101010 and [B]one's-complement =1001, calculate [A-B]two's-complement and indicate whether or not overflow occurs.(Assumed the number system is 8-bit long) [A-B]two's-complement overflow

13. If a RAM’s capacity is 16K words × 8 bits, the address inputs should be bits; We need chips of 8K 8 bits RAM to form a 16 K 32 bits ROM..

14. Which is the XOR gate of the following circuit .

n

15. There are －n invalid states in an n-bit ring counter state diagram.

16. An unused CMOS NOR input should be tied

电子科大数电期末考试题

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to logic level or .

17. The function of a DAC is translating the inputs to the same value of analog outputs.

二、Complete the following truth table of taking a vote by A,B,C, when more than two of A,B,C approve a resolution, the resolution is passed; at the same time, the resolution can’t go through if A don’t agree. For A,B,C, assume 1 is indicated approval, 0 is indicated opposition. For the F, assume 1 is passed, 0 is rejected.（5’）

电子科大数电期末考试题

三、The circuit to the below realizes a combinational function F of four variables. Fill in the Karnaugh map of the logic function F realized by the multiplexer-based circuit. (6’)

F=D∑(0,3,5,6)+D’∑(1,2,4,7)

四、(A) Minimize the logic function expression

F = A·B + AC’

+B’·C+BC’+B’D+BD’+ADE(H+G) （5’）

电子科大数电期末考试题

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F = A·B + AC’ +B’·C+BC’+B’D+BD’ = A·(B ’C)’ +B’·C+BC’+B’D+BD’

= A +B’·C+BC’+B’D+BD’+C’D (或= A +B’·C+BC’+B’D+BD’+CD’)

= A +B’·C+BD’+C’D (或= A + BC’+B’D+CD’)

(B) To find the minimum sum of product for F and use NAND-NAND gates to realize it（6’） F(W,X,Y,Z) Π(1,3,4,6,9,11,12,14)

X’Z’+XZ F=

=( X’Z’+XZ)’’=(( X’Z’)’(XZ)’)’

五、Realize the logic function using one chip of 74LS139 and two NAND gates.（8’）

电子科大数电期末考试题

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F(A,B,C) (2,6)

G(C,D,E) (0,2,3)

F(A,B,C)=C’∑(1,3) G(C,D,E)=C’∑(0,2,3)

六、Design a self-correcting modulo-6 counter with D flip-flops. Write out the excitation equations and output equation. Q2Q1Q0 denote

***

the present states, Q2Q1Q0 denote the next states, Z denote the output. The state transition/output table is as following.（10’）

电子科大数电期末考试题

激励方程式：D2=Q0’ 错 -1分）

D1=Q2 错 -1分）

D0=Q1 错 -1分）

修改自启动：D2=Q0 +Q2Q1’ 错 -1分）

D1=Q2+Q1Q0’ 错 -1分）

D0=Q1+Q2Q0 错 -1分）

输出方程式：Z=Q1’Q0 错 -1分）

2分，2分，

2分，

1分，1分，

1分，

1分， （ （ （ （ （ （ （

电子科大数电期末考试题

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七、Construct a minimal state/output table for a moore sequential machine, that will detect the input sequences: x=101. If x=101 is detected, then Z=1.The input sequences DO NOT overlap one another. The states are denoted with S0~S3.（10’） For example:

X0 1 0 1 0 0 1 0 1 0 1 1 0 1 1 0 0 0 1 1 …

… ：

Z0 0 0 1 0 0 0 0 1 0 0 0 0 1 0 0 0 0 0 0 …

… ：

state/output table

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