11.74LS138是(      )

A.八位緩沖器                                               

B.單穩(wěn)態(tài)觸發(fā)器     

C.八位鎖存器                                               

D.譯碼器

12.在8254的以下幾種工作方式中,具有自動(dòng)重裝初值功能的是(      )

A.方式0                                                       

B.方式1  

C.方式2                                                       

D.方式4

13.8254的一個(gè)計(jì)數(shù)器計(jì)數(shù)結(jié)束時(shí)輸出單拍負(fù)脈沖信號(hào),則其工作在(      )

A.方式0                                                       

B.方式1  

C.方式2                                                       

D.方式3

14.IBM PC/AT機(jī)的內(nèi)部數(shù)據(jù)總線為16位，那么系統(tǒng)總線標(biāo)準(zhǔn)是(      )

A.ISA總線                                                   

B.PCI總線     

C.ISA+PCI總線                                            

D.HOST總線

15.對(duì)于外設(shè)引發(fā)的非屏蔽中斷，CPU的輸入引腳是(      )

A.INTR                                                         

B.INT      

C.NMI                                                          

D.ALE

16.在HDLC高級(jí)數(shù)據(jù)鏈路協(xié)議的幀格式中，作為廣播地址的地址字段是(      )

A.00000000                                                  

B.00001111     

C.11110000                                                   

D.11111111

17.ISA總線I/O讀寫周期是從(      )

A.ALE有效開始的                                        

B.BALE有效開始的      

C. 有效開始的                                        

D. 有效開始的

18.PC機(jī)的可屏蔽硬件中斷結(jié)構(gòu)由8259A中斷控制器組成，其中作為并行口2的中斷口是(      )

A.IRQ₃                                                         

B.IRQ₄    

C.IRQ₅                                                         

D.IRQ₇

19.IEEE1284接口ECP模式中的ECR(擴(kuò)展控制)寄存器，可選擇IEEE1284協(xié)議中除了哪種模式之外的各個(gè)模式？(      )

A.兼容模式                                                  

B.半字節(jié)模式 

C.字節(jié)模式                                                  

D.EPP模式

20.PC機(jī)(PC/AT型)的可屏蔽硬件中斷結(jié)構(gòu)用到的8259A中斷控制器的片數(shù)是(      )

A.1                                                               

B.2   

C.3                                                               

D.4