相关试题
【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？___
【单选题】
8×51的P0采用哪种电路结构？___
A. 集电极开路式输出
B. 基极开路式输出
C. 发射机开路式输出
D. 图腾柱输出
【单选题】
17在8×51里，若要扩展外部存储器时，数据总线连接哪个输入/输出端口？___
【单选题】
点亮一般的LED所耗用的电流约为多少？___
A. 1~5µA
B. 10~20µA
C. 1~5mA
D. 10~20mA
【单选题】
19一般地，蜂鸣器属于哪种负载？___
A. 电阻性负载
B. 电感性负载
C. 电容性负载
D. 不导电负载
【单选题】
7405/7406的输出采用哪种电路结构？___
A. 集电极开路式输出
B. 基极开路式输出
C. 发射机开路式输出
D. 图腾柱输出
【单选题】
21在继电器中，NO接点是一种什么接点？___
A. 不使用接点
B. 不存在接点
C. 激磁后即开路的接点
D. 常开接点
【单选题】
22所谓2P的继电器，代表什么意思？___
A. 只有2个接点
B. 两相的负载
C. 两组电源
D. 2组c接点
推荐试题
【单选题】
Don't forget _________ the window before leaving the room.___
A. to have closed
B. to close
C. having closed
D. closing
【单选题】
Twenty people were______ wounded in the air crash.___
A. quickly
B. wrongly
C. bitterly
D. seriously
【单选题】
The top of the Great Wall is ________ for five horses to go side by side.___
A. wide
B. so wide
C. wide enough
D. enough wide
【单选题】
Nancy is considered to be _________ the other students in her class.___
A. less intelligent
B. the most intelligent
C. intelligent as well
D. as intelligent as
【单选题】
She is not only my classmate __________ also my good friend.___
A. or
B. but
C. and
D. too
【单选题】
I would like to do the job ________ you don't force me to study.___
A. in case
B. although
C. though
D. as long as
【单选题】
__________ she survived the accident is miracle.___
A. What
B. That
C. As
D. Which
【单选题】
I often see _________ the road on his way home.___
A. he cross
B. him cross
C. him crossed
D. he crossing
【单选题】
The workers are busy __________ models for the exhibition.___
A. to make
B. with making
C. being making
D. making
【单选题】
The higher the temperature, __________ the liquid evaporates.___
A. the faster
B. the more fast
C. the slower
D. the more slower
【单选题】
Australia is one of the few countries ___________ people drive on the left of the road.___
A. which
B. that
C. where
D. on which
【单选题】
The grey building is the place where the workers live, and the white building is the place where the spare parts _________ .___
A. are producing
B. are produced
C. produced
D. being produced
【单选题】
Once environmental damage ___________, it takes many years for the system to recover.___
A. is to do
B. does
C. had done
D. is done
【单选题】
We worked hard and completed the task ________.___
A. in the time
B. on the time
C. ahead of time
D. before time
【单选题】
I didn't expect you to turn __________ at the meeting yesterday.___
A. up
B. to
C. out
D. over
【单选题】
Mike is better than Peter _________ swimming.___
【单选题】
Eggs, though rich in nourishments, have ___________ of fat.___
A. a large number
B. the large number
C. a large amount
D. the large amount
【单选题】
His salary as a driver is much higher than _____________.___
A. a porter
B. is a porter
C. as a porter
D. that of a porter
【单选题】
I have been looking forward to__________ from my parents.___
A. hear
B. being heard
C. be heard
D. hearing
【单选题】
The manager will not __________ us to use his car.___
A. have
B. let
C. agree
D. allow
【单选题】
__________ her and then try to copy what she does.___
A. Mind
B. See
C. Stare at
D. Watch
【单选题】
It's bad __________ for you to smoke in the public places where smoking is not allowed.___
A. behavior
B. action
C. manner
D. movement
【单选题】
— I think John and Peter will.___
A. carry out
B. get through
C. take in
D. set aside
【单选题】
If she wants to keep slim, she must make a ________ in her diet.___
A. change
B. turn
C. run
D. go
【单选题】
___________ the War of Independence, the United States was an English colony.___
A.
B. efore B. At
C. In
D. Between
【单选题】
A police officer claimed he had attempted to _________ paying his fare.___
A. avoid
B. reject
C. refuse
D. neglect
【单选题】
He is not seriously ill, but only a _________ headache.___
A. obvious
B. delicate
C. slight
D. temporary
【单选题】
On average, a successful lawyer has to talk to several _________ a day.___
A. customers
B. supporters
C. guests
D. clients
【单选题】
What is the train _________ to Birmingham?___
A. fee
B. tip
C. fare
D. cost
【单选题】
He put forward a theory, _______ of great importance to the progress of science of technology.___
A. I think which is
B. which I think is
C. which is I think
D. I think it is
【单选题】
If the doctor had been available, the child ____________.___
A. would not die
B. could not have died
C. might not die
D. should not have died
【单选题】
The music sounded _______. I enjoyed every minute of it.___
A. well
B. boring
C. wonderfully
D. beautiful
【单选题】
Put it down, Richard. You mustn't read ______letter. ___
A. anyone's else's
B. anyone's else
C. anyone else's
D. anyone else
【单选题】
I saw that she was in difficulty with all those parcels, so I offered my_____.___
A. service
B. money
C. use
D. chance
【单选题】
We were all surprised when he made it clear that he _____________office soon.___
A. leaves
B. would leave
C. left
D. had left
【单选题】
The electric fan has blown away the terrible smell in the hall, ______?___
A. can't it
B. isn't it
C. hasn't it
D. doesn't it
【填空题】
In every cultivated language there are two great classes of words which, taken together, comprise the whole vocabulary. First, there are those words ___ which we become acquainted in daily conversation,
【填空题】
which we ___,that is to say, from the members of our own family and from our familiar associates,
【填空题】
and which we should know and use ___ we could not read or write.
【填空题】
They ___the common things of life,
