【单选题】
24在8×51的程序里，若要将某个输入/输出端口设置成输入功能，应如何处理？___
A. 先输出高电平到该输入/输出端口
B. 先输出低电平到该输入/输出端口
C. 先读取该输入/输出端口的状态
D. 先保存该输入/输出端口的状态
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相关试题
【单选题】
8×51提供几个外部中断和定时器/计数器中断？___
A. 2,2
B. 3,6
C. 2,3
D. 3,7
【单选题】
8×51的IP缓存器的功能如何？___
A. 设置中断优先级
B. 启动中断功能
C. 设置中断触发信号
D. 定义CPU的网址
【单选题】
28若要让采用低电平触发，则应如何设置？___
A. EX0=0
B. EX0=1
C. IT0=0
D. IT0=1
【单选题】
29在Keil µVision3里进行调试/仿真时，在哪里操作才能触动程序中断？___
A. 在Interrupt System
B. 在Cotorl Box对话框里
C. 直接单击魔术棒按钮即可
D. 直接按0键
【单选题】
30在8×51所提供的中断功能里，下列哪个优先级比较高？___
A. T1
B. RI/TI
C. T0
D. INT0
【单选题】
31在TCON缓存里，IE1的功能是什么？___
A. 触发 IE1中断
B. 指示IE1中断的标志
C. 提高IE1优先等级
D. 取消IE1中断
【单选题】
32在Keil C里，中断子程序与函数又何不同？___
A. 中断子程序不必声明
B. 函数不必声明
C. 中断子程序必须有形式参数
D. 中断子程序一定会有返回值
【单选题】
33若要同时启用INT0及INT1中断功能，则应如何设置？___
A. TCON=0×81
B. IE=0×85
C. IP=0×83
D. IE=0×03
【单选题】
35在8×51的Timer里，若使用Mode 0，其最大计数值为多少个机器周期？___
A. 65636
B. 8192
C. 1024
D. 256
【单选题】
36在12MHz的8×51系统里，哪一种方式一次可定时5ms？___
A. Mode 0及Mode 1
B. Mode 1及Mode 2
C. Mode 2及Mode 3
D. Mode3及Mode 1
【单选题】
37若要让Timer作为外部计数只用，应如何设置？___
A. Gate=0
B. Gate=1
C. C/=0
D. C/=1
【单选题】
39下列哪个不是8×51所提供的省电方式？___
A. PD方式
B. IDL方式
C. LP方式
D. 待机方式
【单选题】
89S51的看门狗有何作用？___
A. 重复执行程序
B. 找回遗失数据
C. 复位系统
D. 防止中毒
【单选题】
41若要启用WDT，则应依次填入WDTRST寄存器哪些数据？___
A. 0xe1、0xe2
B. 0xe1、0x1e
C. 0x1e、0xe1
D. 0x10、0x01
【单选题】
8×51的定时器，在下列哪种方式下具有自动加载功能？___
A. Mode0
B. Mode1
C. Mode2
D. Mode3
【单选题】
45下列哪种AD转换器的转换速度比较快？___
A. 双斜率型AD转换器
B. 比较型AD转换器
C. 连续计数式AD转换器
D. 逐渐接近式AD转换器
【单选题】
46下列哪种AD转换器的精密度比较高？___
A. 双斜率型AD转换器
B. 比较型AD转换器
C. 连续计数式AD转换器
D. 逐步逼近式AD转换器
【单选题】
47对于8×8 LED点阵而言，其中的LED个数及引脚各为多少？___
A. 64、16
B. 16、16
C. 64、12
D. 32、12
【单选题】
48在共阳极型8×8 LED点阵里，其阳极如何连接？___
A. 各行阳极连接到行引脚
B. 各列阳极连接到列引脚
C. 各行阳极连接到列引脚
D. 各列阳极连接到行引脚
【单选题】
49在共阳极型8×8 LED点阵里，其阴极如何连接？___
A. 各行阴极连接到行引脚
B. 各列阴极连接到列引脚
C. 各行阴极连接到列引脚
D. 各列阴极连接到行引脚
【单选题】
50双色8×8 LED点阵的列引脚与行引脚各位多少？___
A. 12、12
B. 8、16
C. 16、8
D. 24、8
【单选题】
___的方向规定由高电位点指向低电位点。
【单选题】
三相电动势到达最大的顺序是不同的，这种达到最大值的先后次序，称三相电源的相序，相序为U-V-W-U，称为___。
【单选题】
电路的作用是实现能量的传输和转换、信号的___和处理。
【单选题】
电阻器反映导体对电流起阻碍作用的大小，简称___。
A. 电动势
B. 功率
C. 电阻率
D. 电阻
【单选题】
___反映了在不含电源的一段电路中，电流与这段电路两端的电压及电阻的关系。
A. 欧姆定律
B. 楞次定律
C. 部分电路欧姆定律
D. 全欧姆定律
【单选题】
并联电路中的总电流等于各电阻中的___。
A. 倒数之和
B. 相等
C. 电流之和
D. 分配的电流与各电阻值成正比
【单选题】
串联电路中流过每个电阻的电流都___。
A. 电流之和
B. 相等
C. 等于各电阻流过的电流之和
D. 分配的电流与各电阻值成正比
【单选题】
___的一端连在电路中的一点，另一端也同时连在另一点，使每个电阻两端都承受相同的电压，这种联结方式叫电阻的并联。
A. 两个相同电阻
B. 一大一小电阻
C. 几个相同大小的电阻
D. 几个电阻
【单选题】
___的电阻首尾依次相连，中间无分支的联结方式叫电阻的串联。
A. 两个或两个以上
B. 两个
C. 两个以上
D. 一个或一个以上
【单选题】
电流流过负载时，负载将电能转换成___。
A. 机械能
B. 热能
C. 光能
D. 其他形式的能
【单选题】
电功的数学表达式不正确的是___。
A. W=Ut/R2t
B. W=UIt
C. W=U2t/Rt
D. W=I2Rt
【单选题】
测量电压时，电压表应与被测电路___。
【单选题】
测量电流时,万用表的接线方法与直流电流表一样，应把万用表___在电路中。测量直流电压时，应把万用表与被测电路并联。
【单选题】
串联电路中各电阻两端电压的关系是___。
A. 各电阻两端电压相等
B. 阻值越小两端电压越高
C. 阻值越大两端电压越高
【单选题】
确定正弦量的三要素为 ___。
A. 相位、初相位、相位差
B. 最大值、频率、初相角
C. 周期、频率、角频率
【单选题】
当电压为5V时,导体的电阻值为5欧,那么当电阻两端电压为2V时,电阻值为___欧。
【单选题】
对称负载接成星形时,三相总电流___。
A. 等于零
B. 等于其中一相电流的三倍
C. 等于其中一相电流。
推荐试题
【单选题】
Many frogs ___ the sound of their voice using special sacs(囊) in their throat.
A. amplify
B. widen
C. expand
D. enlarge
【单选题】
Some old people don’t like pop songs because they cannot ___ so much noise.
A. resist
B. sustain
C. tolerate
D. undergo
【单选题】
I have kept that portrait where I can see it every day, as it always ___ me of my university days in London.
A. recollects
B. reminds
C. recalls
D. invokes
【单选题】
The article suggests that when a person is under unusual ___ he should be especially careful to have a well-balanced diet.
A. weight
B. stress
C. press
D. nerve
【单选题】
You should hire a more ___ manager than the one you currently have.
A. sufficient
B. effective
C. respective
D. efficient
【单选题】
Surgeons began to ___ their hands and arms with soap and water before operating.
A. scrub
B. enhance
C. rub
D. exhibit
【单选题】
He might let something ___ in a moment of weakness.
A. slip
B. leak
C. to slip
D. to leak
【单选题】
Do not ___ the salad until you are ready to serve.
A. mix
B. toss
C. fling
D. eat
【单选题】
The ___ for which he had fought all his life no longer seemed important to him.
A. aims
B. objectives
C. subjects
D. goals
【单选题】
You should pause and ___ now.
A. tweet
B. ponder
C. squander
D. gossip
【单选题】
Eating too much fat can ____heart disease and cause high blood pressure.
A. contribute to
B. attribute to
C. attest to
D. devote to
【单选题】
It soon ___ that what she loved was not my person but my wealth.
A. widened
B. expanded
C. extended
D. developed
【单选题】
I want to buy a new tie to ___ this brown suit.
A. go into
B. go after
C. go with
D. go through
【单选题】
Our company decided to ___ the contract because a number of the conditions in it had not been met.
A. destroy
B. resist
C. assume
D. cancel
【单选题】
My first ___ was to turn and run.
A. institute
B. institution
C. instinct
D. tuition
【单选题】
I think it’s time I ___ in a new computer.
A. invested
B. insulted
C. interacted
D. impacted
【单选题】
The jeweler will ____ the inside of the ring with her name.
A. carve
B. engrave
C. cut
D. engross
【单选题】
He was bleeding from a _____ on his forehead.
A. lash
B. gash
C. ash
D. sash
【单选题】
Let us go to the next ______ on the agenda.
A. matter
B. debate
C. speech
D. item
【单选题】
They are _____ moving their office outside London.
A. considered
B. discussing
C. pondering
D. negotiating
【单选题】
Although she _____ the old pot thoroughly, she could not make it look completely clean.
A. scrubbed
B. washed
C. made
D. screwed
【单选题】
The mistake will remain an indelible ____ on his memory.
A. stain
B. thing
C. issue
D. accident
【单选题】
The wheel ____ through my frozen hand, and the car went right across the road.
A. slipped
B. sipped
C. dashed
D. disappeared
【单选题】
The cupboard was ____ with old fishing tackle.
A. stuffed
B. stocked
C. stored
D. filled
【单选题】
The decision depended on the ____ of a coin.
A. loss
B. lot
C. toss
D. sign
【单选题】
Teaching can be a tiring and ____ job.
A. meaningless
B. stressed
C. rewarded
D. stressful
【单选题】
The building is partly a museum and partly a private ____.
A. place
B. area
C. community
D. residence
【单选题】
Stop ______ your foot.
A. tossing
B. wiggling
C. exhibiting
D. reviewing
【单选题】
It was a bloody ___ between the two armies.
A. rebellion
B. encounter
C. meet
D. fight
【单选题】
They conferred on the best way to ______ business.
A. extend
B. adjust
C. expand
D. adopt
【单选题】
We had a party last month, and it was a lot of fun, so let’s have ____ one this month.
A. another
B. the other B. more D. other
【单选题】
I decided to go to the library as soon as I ____.
A. finish what I did
B. finished what I did
C. would finish what I was doing
D. finished what I was doing
【单选题】
The speaker, ______ for her splendid speeches, was warmly received by the audience.
A. having known
B. being known
C. knowing
D. known
【单选题】
No sooner had we reached the top of the hill ______ we all sat down to rest.
A. when
B. then
C. than
D. until
【单选题】
___ energy under the earth must be released in one form or another, for example, an earthquake.
A. Accumulated
B. Gathered
C. Assembled
D. Collected
【单选题】
Please ___ me for my rudeness. I really do not know the custom here.
A. engaged
B. comfort
C. execute
D. forgive
【单选题】
Sometimes it is very difficult to ___ some of the English words. Even the native speaker cannot help.
A. decrease
B. create
C. define
D. delight
【单选题】
In the wife’s eyes, his ___ to their marriage life is far from perfect.
A. requirement
B. commitment
C. participation
D. reflection
【单选题】
This newspaper often ___ the government’s opinion, not the public opinion.
A. affects
B. reacts
C. reflects
D. recognizes
【单选题】
It is predicted that heavy rains are ___ to flood the area in a few days.
A. frightening
B. threatening
C. scattering
D. warning
