问题 单项选择题

下面关于8237可编程DMA控制器的叙述中,错误的是

A.8237中4个通道的方式寄存器共用一个端口地址

B.8237每个通道在每次DMA传输后,其当前字节计数器的值可通过编程设置成自动加1或减1

C.8237每个通道有单字节传送方式、数据块传送方式、请求传送方式和级联传输方式

D.8237在固定优先级情况下,DREQ0优先级最高,DPEQ3优先级最低

答案

参考答案:B

解析: 本题考查8257工作原理。当前地址寄存器的值在每次DMA传输后自动加 1或减1,为传输下一个字节作好准备,并不需要通过编程设置,所以B是错的。

单项选择题
完形填空
As a young man, Al was a skilled artist, a potter. He had a wife and two fine sons. One night, his oldest son   36  a severe stomachache and died suddenly. To make matters worse, his wife left him a short time later,   37  him alone with his six-year- old younger son. The hurt and pain of the two situations were _ 38 _ Al could handle, and he _ 39  to alcohol. Al began to lose everything he possessed---his home, his land, his art objects, everything.   40  he died alone in a San Francisco motel room.
When I heard of Al’s death, I reacted with the same disdain(蔑视)the world shows for one who ends his life with nothing   41 _ left. “What a complete failure!” I thought. “What a totally   42__  life!”
As time went by, I began to re-evaluate my earlier _ 43  judgment. You see, I knew Al’s now adult son, Ernie. He is one of the kindest, most   44  most loving men I have ever known. I watched Ernie with his children and saw the free   45  of the love between them. I knew that kindness and caring had to come   46  somewhere.
I hadn’t heard Ernie talk much about his father. It is so hard to   47  an alcoholic. One day I get up my   48  to ask him. “I’m really puzzled by something,” I said. “I know your father was basically the only one to   49  you.   50  on earth did he do that you became such a special person?
Ernie sat _ 51 _ and thought for a few moments. Then he said, “From my  _52   memories as a child until I left home at 18, Al came into my room every night, gave me a __53  and said, “I love you, son.”
Tears came to my eyes as I realized what a fool I had been to   54  Al as a failure. He had not left any material possession behind,   55  he left behind one of the finest, most giving men I have ever known.
小题1:
A.obtainedB.developedC.curedD.recovered
小题2:
A.takingB.lockingC.findingD.leaving
小题3:
A.more thanB.less thanC.other than D.rather than
小题4:
A.got B.turnedC.lovedD.changed
小题5:
A.LuckilyB.SuddenlyC.EventuallyD.Jokingly
小题6:
A.materialB.expensiveC.realD.special
小题7:
A.happyB.thoughtfulC.desertedD.wasted
小题8:
A.angryB.sharpC.actualD.proper
小题9:
A.handsomeB.richC.caringD.ordinary
小题10:
A.flowB.riseC.flyD.move
小题11:
A.outB.fromC.upD.down
小题12:
A.defendB.becomeC.discussD.argue
小题13:
A.confidenceB.courageC.beliefD.strength
小题14:
A.feedB.loveC.careD.raise
小题15:
A.HowB.WhatC.WhyD.Which
小题16:
A.angrilyB.comfortably C.quietlyD.excitedly
小题17:
A.earliestB.nearestC.bestD.hardest
小题18:
A.patB.lessonC.kissD.present
小题19:
A.judgeB.sayC.rememberD.respect
小题20:
A.soB.andC.butD.or