电子科技大学期末数字电子技术考试题a卷-参考答案教学内容

电子科技大学二零零九至二零一零学年第 二 学期期 末 考试

数字逻辑设计及应用 课程考试题 A 卷（120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 20 分， 期中 20 分， 实验 0 分， 期末 60 分

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

C. [ 1010011 ]GRAY =[

10011000 ]8421BCD

3. If ∑=C B A F ,,)6,3,2,1(, then F D ∑=C B A ,,( 1，4，5，6 )=C B A ,,∏(0，2，3，7 ).

4. If the parameters of 74LS-series are defined as follows: V OL max = 0.5 V , V OH min = 2.7 V , V IL max = 0.8 V , V IH min = 2.0 V , then the low-state DC noise margin is 0.3V ,the high-state DC noise margin is 0.7V .

5. Assigning 0 to Low and 1 to High is called positive logic. A CMOS XOR gate in positive logic is called XNOR gate in negative logic.

6. A sequential circuit whose output depends on the state alone is called a Moore machine.

7. To design a "001010" serial sequence generator by shift registers, the shift register should need 4 bit as least.

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

8state 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 function D= JQ'+K'Q.

10.Which state in Fig. 1 is ambiguous D

11.A CMOS circuit is shown as Fig. 2, its logic function z= A’B’+AB

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 = 01110000, overflow no

13. If a RAM’s capacity is 16K words × 8 bits, the address inputs should be 14bits; We need 8chips of 8K ⨯8 bits RAM to form a 16 K ⨯ 32 bits ROM..

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

15.There are 2n－n invalid states in an n-bit ring counter state diagram.

16.An unused CMOS NOR input should be tied to logic Low level or 0 .

17.The function of a DAC is translating the Digital 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 thr ough if A don’t agree.For A,B,C, assume 1 is indicated approval, 0 is indicated opposition. For the F,

A B C F