问题 单项选择题

高速设备以DMA方式工作时,CPU放弃总线控制权交给DMA控制器控制系统总线,实现设备与主存间的数据交换。DMA传送前,CPU对DMA控制器进行()工作。

A.预置主存首地址

B.预置交换数据个数

C.预置读/写命令

D.预置主存首地址、交换数据个数及读/写命令

答案

参考答案:D

解析:

高速设备进行DMA方式传送数据时,CPU交出系统总线控制权,由DMA控制器控制总线,实现存储器和设备直接交换数据。这时由DMA控制器给出访问存储器的首地址,交换数据个数,及读/写性质。而DMA本身没有这些控制信息,必须由CPU在DMA方式传送前对DMA控制器进行预置,才能进行DMA方式的数据传送。

完形填空

Since my family were not going to be helpful about my taking a cooking job, I decided I  1  look for one all by myself and   2   them about it till I'd get one. I had seen an agency advertised   3   a local paper, so   4  there was no one about to say “ Where are you going? ”, I rushed out of the house   5  it. I was widely   6   and was nervous as if I   7  on the stage. Finding the place quite easily, I tore up three flights of stairs, and swung breathlessly  8   a door which said “ Enter without knocking, if you   9  . ”   

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1.A.would       B.ought       C.wanted     D.liked

2.A.told    B.not tell     C.not told    D.not to tell

3.A.on      B.at     C.for   D.in

4.A.as soon as B.as to        C.far    D.as

5.A.search for B.in search of     C.finding    D.looked for

6.A.excited      B.worried    C.exciting   D.worrying

7.A.was going B.were coming   C.was coming     D.were going

8.A.through     B.by    C.in     D.to

9.A.pleased      B.pleasant   C.please      D.pleasure

10.A.calmed       B.excited     C.moved      D.frightened

11.A.opposite     B.against     C.back        D.face

12.A.glass   B.glasses     C.eyes D.eye

13.A.while B.before      C.after        D.when

14.A.rather  B.fairly       C.too   D.little

15.A.it        B.that C.know       D.it known

16.A.how    B.why C.whether   D.where

17.A.were   B.should be        C.would be D.was

18.A.experience B.experiment      C.time        D.money

19.A.In a fact     B.As a matter of fact   C.As to fact     D.As a matter

20.A.a very        B.very a       C.very the   D.this very

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