相关试题
【单选题】
28十进制数25用8421BCD码表示为___。4位
A. 10 101
B. 0010 0101
C. 100101
D. 10101
【单选题】
29与十进制数（53.5）10不等值的数或代码为___。
A. (0101 0011.0101)8421BCD
B. (35.8)16
C. (110101.1)2
D. (60.4)8
【单选题】
30与八进制数(47.3)8等值的数为___
A. (100111.011)2
B. (97.3)16
C. (27.3 )16
D. (100111.11)2
【单选题】
31下列各型号中属于优先编码器是___。
A. 74LS85
B. 74LS138
C. 74LS148
D. 74LS48
【单选题】
七段数码显示器BS202是___。
A. 共阳极LED管
B. 共阴极LED管
C. 共阳极LCD管
D. 共阴极LCD管
【单选题】
33八输入端的编码器按二进制数编码时，其输出端的个数是___。
【单选题】
四输入的译码器，其输出端最多为___。
A. 4个
B. 8个
C. 10个
D. 16个
【单选题】
当74LS148的输入端按顺序输入11011101时，输出为___。
A. 101
B. 010
C. 001
D. 110
【单选题】
用三线-八线译码器74LS138和辅助门电路实现逻辑函数Y=a2+a1a2，应___。
A. 用与非门，Y=y0y1y4y5y6y7
B. 用与门，Y=y2y3
C. 用或门，Y=y2+y3
D. 用或门，Y=y0+y1+y4+y5+y6+y7
【单选题】
37时序逻辑电路中一定包含___。
A. 触发器
B. 组合逻辑电路
C. 移位寄存器
D. 译码器
【单选题】
仅具有置“0”和置“1”功能的触发器是___。
A. 基本RS触发器
B. 钟控RS触发器
C. D触发器
D. JK触发器
【单选题】
由与非门组成的基本RS触发器不允许输入的变量组合为___。
【单选题】
40仅具有保持和翻转功能的触发器是___。
A. JK触发器
B. T触发器
C. D触发器
D. T' 触发器
【单选题】
触发器由门电路构成，但它不同于门电路功能，主要特点是___。
A. 具有翻转功能
B. 具有保持功能
C. 具有记忆功能
【单选题】
TTL集成触发器直接置0端[]和直接置1端[]在触发器正常工作时应___。
A. =1，=0
B. =0，=1
C. 保持高电平“1”
D. 保持低电平“0”
【单选题】
按逻辑功能的不同，双稳态触发器可分为___。
A. RS、JK、D、T等
B. 主从型和维持阻塞型
C. TTL型和MOS型
D. 上述均包括
【单选题】
同步计数器和异步计数器比较，同步计数器的显著优点是___。
A. 工作速度高
B. 触发器利用率高
C. 电路简单
D. 不受时钟CP控制。
【单选题】
把一个五进制计数器与一个四进制计数器串联可得到___进制计数器。
【单选题】
下列逻辑电路中为时序逻辑电路的是___ 。
A. 变量译码器
B. 加法器
C. 数码寄存器
D. 数据选择器
【单选题】
47N个触发器可以构成最大计数长度{进制数}为___ 的计数器。
【单选题】
N个触发器可以构成能寄存___位二进制数码的寄存器。
【单选题】
49五个D触发器构成环形计数器，其计数长度为___。
【单选题】
同步时序电路和异步时序电路比较，其差异在于后者___。
A. 没有触发器
B. 没有统一的时钟脉冲控制
C. 没有稳定状态
D. 输出只与内部状态有关
【单选题】
一位8421BCD码计数器至少需要___个触发器。
【单选题】
某电视机水平-垂直扫描发生器需要一个分频器将31500HZ的脉冲转换为60HZ的脉冲，欲构成此分频器至少需要___个触发器。
A. 10
B. 60
C. 525
D. 31500
【单选题】
555定时器属于___
A. 时序逻辑电路
B. 组合逻辑电路
C. 模拟电子电路
【单选题】
54多谐振荡器可产生 ___
A. 正弦波
B. 矩形脉冲
C. 三角波
D. 锯齿波
【单选题】
脉冲整形电路有___。
A. 多谐振荡器
B. 施密特触发器
C. 555定时器
【单选题】
56石英晶体多谐振荡器的突出优点是___ 。
A. 速度高
B. 电路简单
C. 振荡频率稳定
D. 输出波形边沿陡峭
【单选题】
TTL单定时器型号的最后几位数字为___。
A. 555
B. 556
C. 7555
D. 7556
【单选题】
555定时器不可以组成___。
A. 多谐振荡器
B. 单稳态触发器
C. 施密特触发器
D. JK触发器
【单选题】
59以下各电路中，___可以产生脉冲定时。
A. 多谐振荡器
B. 单稳态触发器
C. 施密特触发器
D. 石英晶体多谐振荡器
【单选题】
555定时电路端不用时，应当___。
A. 接高电平
B. 接低电平
C. 通过0.01µF的电容接地
D. 通过小于500Ω的电阻接地
【单选题】
89S51的内部程序存储器与数据存储器容量各为多少？___
A. 64KB、128B
B. 4KB、64KB
C. 4KB、128B
D. 8KB、256B
【单选题】
89S51比89C51多出了哪个功能？___
A. 存储器加倍
B. 具有WDT工能
C. 多了一个8位输入/输出端口
D. 多了一个串行口
【单选题】
6在DIP40封装的8×51芯片里，复位RESET引脚的引脚编号是什么？___
【单选题】
7在DIP40封装的8×51芯片里，接地引脚与电源引脚的引脚编号是什么？___
A. 1、21
B. 11.31
C. 20、40
D. 19、39
【单选题】
9在12MHz始终脉冲的8051系统里，一个机器周期有多长？___
A. 1µs
B. 12µs
C. 1ms
D. 12ms
【单选题】
12下列哪个寄存器是8×51内的16位寄存器？___
【单选题】
14在8×51的输入/输出端口里，哪个输入/输出端口执行在输出功能时没有内部上拉电阻？___
推荐试题
【单选题】
Q2: What is the most exciting finding about increasing positive emotions?___
A. It improves relationships .
B. It leads to greater success .
C. It helps develop creativity .
D. It contributes to good health .
【单选题】
Q3: What does the speaker say about negative feelings?___
A. People should turn every negative feeling around .
B. Negative feelings can sometimes have positive effects .
C. Negative feelings often cause people to make mistakes .
D. People should never show negative feelings in public places .
【单选题】
Q4: What is the main idea of the passage?___
A. People should learn to manage their emotions .
B. People should be patient with their negative feelings .
C. People should learn to analyze causes of unhappiness .
D. People should identify as many positive feelings as possible .
【单选题】
Q1: What are the man and woman talking about?___
A. Whether nature is magical and kind .
B. Whether nature is powerful and full of risks .
C. Whether Christopher was well prepared for the trip .
D. Whether Christopher's trip to Alaska was worthwhile .
【单选题】
Q2: What can we learn about Christopher?___
A. He made a film about his trip to Alaska .
B. He wrote a story about his trip to Alaska .
C. He died while having an adventure in Alaska .
D. He learned how powerful and risky Alaska was .
【单选题】
Q3: What does the woman think about Christopher taking the trip to Alaska?___
A. He was too foolish .
B. He was really romantic .
C. He had a very kind heart .
D. He had a spirit for trying things .
【单选题】
Q4: Which of the following is NOT mentioned as something that would have saved Christopher’s life?___
A. A gun to hunt .
B. The map of the area .
C. Emergency food supplies .
D.
E. mergency communication equipment .
【单选题】
Q1: What speed can an avalanche reach within five seconds of taking off?___
A. At 8 miles an hour .
B. At 18 miles an hour .
C. At 80 miles an hour .
D. At 88 miles an hour .
【单选题】
Q2: According to the passage, under what circumstances may an avalanche occur?___
A. There are too many layers of snow on the .
B. There is a layer of snow covering an entire area .
C. The top layer of snow slides off the layer below it .
D. The layer of snow below the surface becomes unstable .
【单选题】
Q3: What are skiers advised to do to avoid being caught in an avalanche?___
A. Ski only in the official ski areas .
B. Look for solid snow to walk on .
C. Look out for each other while skiing .
D. Learn to control themselves in an avalanche .
【单选题】
Q4: Why does the ski patrol use explosives?___
A. To dig holes in the snow .
B. To close the area for skiing .
C. To make an avalanche move on purpose .
D. To' check how different layers are holding up .
【单选题】
Q1:What is conversation mainly about?___
A. The woman's happy college life the man's doubt .
B. The woman's spending habits and the man's concerns .
C. The man's reminding the woman of the exam this Thursday .
D. The man's support for the woman over the past 15 years .
【单选题】
Q2:What did the woman do last night?___
A. She bought a new leather coat .
B. She studied very hard for an exam .
C. She treated all her friends to dinner .
D. She went to a concert with her friends .
【单选题】
Q3:Where did the woman get the money?___
A. She just received her student loan .
B. She saved some money for herself .
C. She borrowed the money from her friends .
D. She asked her mom to send her the money .
【单选题】
Q4:What is the man?___
A. A teacher of biology .
B. An undergraduate student .
C. A freshman in biology class .
D. A graduate teaching assistant .
【单选题】
Q1: What is this passage mainly about?___
A. How businesses can compete with each other .
B. How small businesses operate during holidays .
C. How small businesses manage holiday workers .
D. How can earn more money during holidays .
【单选题】
Q2: According to Rubin, what can small companies do to thank holiday workers?___
A. Have talks with their families .
B. Give them good extra benefits .
C. Offer them expensive holiday tokens .
D. Show appreciation to them face to face .
【单选题】
Q3: What can small business owners do to help holiday workers get into the holiday spirit?___
A. Entertain them with big meals .
B. Let them enjoy some holiday games .
C. Give them handmade thank-you cards .
D. Send their families some holiday gift cards .
【单选题】
Q4: Who are supposed to benefit most from this passage?___
A. Workers who have to work during holidays .
B. Employees who intend to earn extra money .
C. Big companies that usually close on holidays .
D. Small businesses that try to be more competitive .
【单选题】
In the first two paragraphs of the passage the writer tries to tell us that___
A. he had lived in Washington D.C. for twenty years
B. he was very imaginative when he was a child
C. he had fond memories of his old neighborhood
D. )he had come from a very poor neighborhood
【单选题】
The writer ,as a child ,was very fond of playing in the basement because ___
A. it was bright and alive
B. it contained a movie house and a space station
C. it was ideal for playing hide-and-seek
D. it was surrounded by trees and flowers
【单选题】
How did the writer feel when he visited his old neighborhood in Washington D.C. ?___
A. Greatly surprised .
B. Very regretful .
C. Quite excited .
D. Very sad .
【单选题】
On his visit to his hometown ,the writer found the old apartment building___
A. see medunfit to live in
B. had been repaired
C. could hardly be recognized
D. looked dirty and smelt horrible
【单选题】
" Youcan never go home again "inthe last sentence of this passage means that___
A. one should never revisit his hometown after many years of absence
B. one will never find his hometown the same as it was in his childhood memory
C. avisit to one's hometown will bring back one's fond memories of home
D. avisit to one's hometown will bring back many sad memorie
【单选题】
We learn from the passage that Tracy died___
A. on December 8,1992
B. of brain damage
C. 24 hours after he fell off the roof of a car
D. in a car crash
【单选题】
Tracy's parents decided to donate Tracy's organs because___
A. Tracy told them to do so just before he died
B. they wanted to save others the pain of seeing a dear one die
C. David's life could continue in a meaningful way
D. they knew David was suffering from a hopeless liver disease
【单选题】
The meeting between the writer's family and Tracy's parents was arranged because___
A. the writer and her husband wished to express their thanks to Tracy's parents
B. the local organ bank wanted to see how both families felt about the donation
C. Tracy's parents wanted to see someone whose life had been saved by the donation
D. the two families were linked by the most bittersweet ties imaginable
【单选题】
The writer and her husband learned how Tracy died___
A. from his parents
B. from the organ bank
C. from the hospital
D. from the doctor who performed the operation
【单选题】
The meeting between the two families helped to ease the Marshes'suffering because___
A. they saw that David looked very much like their son
B. they saw that David had regained health with Tracy's liver
C. they now had someone to share their memories of Tracy
D. they now knew for sure they had done the right thing
【单选题】
The writer's first marriage was unsuccessful because___
A. her husband often woke her up at midnight
B. her husband kept criticizing her
C. she was so unattractive
D. she had a self-esteem problem
【单选题】
When the writer asked for a divorce ,her husband___
A. told her that she would never find one who loved her as he did
B. delayed two years before giving her a reply
C. accused her of having an affair
D. said that she was unattractive and not worth loving
【单选题】
When the writer first met Clint ,she felt that___
A. she should have listened to her friend and met Clint earlier
B. Clint was a nice ,dazzling young man
C. Clint could not be really interested in her
D. she would find true love in Clint
【单选题】
The writer was particularly touched by Clint because___
A. he loved her children and asked for their approval of the marriage
B. he said that he could not imagine a life without her and the children
C. he believed that at 2 and 4 ,the two children were the "menof the house "
D. hekept her company and talked with her until the next morning
【单选题】
The writer's marriage to Clint is important to her mainly because___
A. it gave her and her sons a second chance to live a happy life
B. every day Clint would tell the writer that he loved her
C. it helped her to regain her self respect
D. it made her children happy ,which is all she cared about in life
【单选题】
What was Goodall's childhood dream ?___
A. She dreamed of going to college .
B. She dreamed of studying animals in Africa .
C. She dreamed of becoming a scientist .
D. She dreamed of traveling all around the world .
【单选题】
What did Goodall's mother think of her dream ?___
A. As a girl she should not go to the African jungle .
B. Her dream would remain a dream unless she got the right training .
C. As a girl she should stay away from violent animals .
D. She could make her dream come true if she was determined .
【单选题】
Goodall's most important discovery was that___
A. some animals use tools
B. like humans animals have emotions
C. chimpanzees could attack each other violently
D. termites are chimpanzees'favorite food
【单选题】
Goodall's success is chiefly due to her___
A. exceptional talents
B. scientific training
C. determination and patience
D. enthusiasm and good luck
【单选题】
What is Goodall doing now ?___
A. Studying animal behavior at Cambridge University .
B. Raising funds for the preservation of wildlife .
C. Observing chimpanzees in African jungles .
D. Working hard supervising postgraduate students.
【单选题】
___是我们理解当前所处历史方位的关键词。
A. 新时期
B. 新时代
C. 重要战略机遇期
D. 关键期
