问题 单项选择题

以下叙述中错误的是______。

A.实时系统就是响应快的系统

B.JTAG主要用于芯片内部测试及系统调试

C.嵌入式系统在开发过程中,下载bootloader可以采用Jtag接口

D.触摸屏是一种输入输出设备

答案

参考答案:A

解析:实时系统是一种特殊的嵌入式系统,其正确性不仅依赖系统计算的逻辑结果,还依赖于产生这个结果的时间。实时系统不是响应快的系统,而是能够在指定或者确定的时间内完成系统功能和外部或内部、同步或异步时间做出响应的系统。 JTAG是一种国际标准测试协议(IEEE 1149.1兼容),主要用于芯片内部测试。基本原理是在器件内部定义一个TAP(Test Access Port测试访问口)通过专用的JTAG测试工具对内部节点进行测试。JTAG测试允许多个器件通过JTAG接口串联在一起,形成一个JTAG链,能实现对各个器件分别测试。 现今多数的高级器件都带有JTAG接口,支持JTAG协议,如DSP、FPGA、ARM、部分单片机器件等,方便多目标系统进行测试,同时还可以实现ISP(In-System Programmable在线编程),对FLASH等器件进行编程。 触摸屏(touch screen)是一种可接收触头等输入信号的感应式液晶显示装置,当接触了屏幕上的图形按钮时,屏幕上的触觉反馈系统可根据预先编程的程式驱动各种连接装置,可用以取代机械式的按钮面板,并借由液晶显示画面制造出生动的影音效果。触摸屏作为一种最新的电脑输入输出设备,是目前最简单、方便、自然的一种人机交互方式,主要应用于公共信息的查询、领导办公、工业控制、军事指挥、电子游戏、点歌点菜、多媒体教学、房地产预售等。

阅读理解

阅读理解。

     After graduation I returned home to my small town in Indiana. I didn't have a job yet. Mr. Hobbs, a

friend of my father's, owned a small shirt factory in town. Within the past five years it had grown from

twenty to eighty workers. Mr. Hobbs was worried that his plant was getting too big and inefficient, so he

asked me to come in on a short-term basis as a consultant.

    I went to the plant and spent about a week looking around and making notes. I was really a mazed at

what I saw.

    Most curious of all, there was no quality control at all. No one inspected the final product of the factory. As a result some of the shirts that were put in boxes for shipment were missing one or two buttons, the

collar, and even a sleeve sometimes!

    The working conditions were poor. The tables where the workers sat were very high and

uncomfortable. Except for a half hour at lunchtime, there were no breaks in the day to relieve the boring

work. There was no music. The walls of the workrooms were a dull gray color. I was amazed that the

workers hadn't gone on strike.

    Furthermore, the work flow was irregular. There was one especially absent-minded young man in the

assembly (组装) line who sewed on buttons. After a while I recognized him as "Big Jim", who used to sit

behind me in math class in high school. He was very slow and all the shifts were held up at his position.

Workers beyond him in line on his shift had to wait with nothing to do; therefore, a great deal of time and

efficiency were lost as Big Jim daydreamed while he worked. All week I wondered why he wasn't fired.

    After I made observations for a week, Mr. Hobbs asked me for an oral report of my findings.

1. The shirts from Mr. Hobbs' factory can be described as ____.

A. of low quality    

B. of high quality  

C. fashionable  

D. unfashionable

2. Why did Mr. Hobbs ask the writer to the factory?

A. The factory was too big.

B. The factory was not producing fast enough.

C. The factory was not big enough.

D. The writer was a college graduate.

3. Which is not likely to happen in the factory?

A. The workers will have more rest in the day.    

B. Someone will examine the final product.

C. New machines will be bought.             

D. The factory will be repainted.

4. Big Jim may get fired mainly because ____.

A. he was slow                                  

B. he wasted much time

C. he was absent-minded                  

D. the work flow was irregular

单项选择题