输入输出程序设计

第8章输入输出程序设计8.1I/O设备的数据传送方式一、CPU与外设控制信息状态信息数据信息二、直接存储器存取（DMA）方式系统完成DMA传送的步骤如下:(1)DMA控制器向CPU发出HOLD信号,请求使用总线.(2)CPU发出响应信号HOLD给DMA控制器,并将总线让出.(3)传输数据的存储器地址通过地址总线发出.(4)传输的数据字节通过数据总线进行传输.(5)地址寄存器增1,以便指向下一个要传送的字节.(6)字节计数器减1.(7)若字节计数器非0,转向第3步.(8)否则,DMA控制器撤消总线请求信号HOLD,传送结束8.2程序直接控制I/O方式一、I/O端口I/O地址功能I/O地址功能00~0FDMA控制器8237A20~3F可编程中断控制器8259A40~5F可编程中断计时器60~638255APPI70~71CMOSRAM81~8FDMA页表地址寄存器93~9FDMA控制器A0~A1可编程中断控制器2C0~CEDMA通道,传输地址寄存器F0~FF协处理器170~1F7硬盘控制器200~20F游戏控制端口278~27A3号并行口(LPT2打印机)2E0~2E3EGA/VGA使用2F8~2FE2号串行口(COM2)320~324硬盘适配器366~36FPC网络372~377软盘适配器378~37A2号并行口(LPT1打印机)380~38FSDLC及BSC通信390~393Cluster适配器3A0~3AFBSC通信3B0~3BFMDA视频寄存器3BC~3BE1号并行口3C0~3CFEGA/VGA视频寄存器3D0~3D7CGA视频寄存器3F0~3F7软盘控制寄存器3F8~3FE1号串行口(COM1)表8.1I/O端口地址分配二、I/O指令INAL,PORT;(AL)（PORT）INAX,PORT;(AX)（PORT+1,PORT）INAL,DX;(AL)（(DX)）INAX,DX;(AL)（(DX+1),(DX)）OUTPORT,AL;（PORT）(AL)

OUTPORT,AX;（PORT+1,PORT）(AX)

OUTDX,AL;（(DX)）(AL)

OUTDX,AX;（(DX+1),(DX)）(AL)

例如:INAX,28HMOVDATA_WORD,AXINAL,27HTESTAL,00000100BJNZERRORMOVDX,126HINAL,DXORAL,80HOUTDX,AL三、I/O程序举例例8.1发声子程序SOUND1/0076543210控制其他外部设备2号定时器门控&放大器程序如下:SOUNDPROCNEARPUSHAXPUSHDXMOVDX,CXINAL,61HANDAL,11111100BTRIG:XORAL,2OUT61H,ALMOVCX,BXDELAY:LOOPDELAYDECDXJNETRIGPOPDXPOPAXRETSOUNDENDP例8.2打印字符的程序段PRT_CHARDATASEGMENTMESSDB‘PRINTERISMORMAL’,0DH,0AHCOUNTEQU$-MESSDATAENDSCSEGSEGMENTMAINPROCFARASSUMECS:CSEG,DS:DATASTART:MOVSI,OFFSETMESSMOVCX,COUNTNEXT:MOVDX,379HWAIT:INAL,DXTESTAL,80HJEWAITMOVAL,[SI]MOVDX,378HOUTDX,ALMOVAL,0DHMOVDX,37AHOUTDX,ALMOVAL,0CHOUTDX,ALINCSILOOPNEXTMOVAH,4CHINT21HMAINENDPCSEGENDSENDSTART例8.3CPU要从3个设备轮流输入数据,PROC1,PROC2,PROC3分别是设备1,设备2和设备3的数据输入程序.它们的状态寄存器的端口地址分别用STAT1,STAT2,STAT3表示,这三个状态寄存器的5位是输入准备好.INPUT:INAL,STAT1TESTAL,20HJZDEV2CALLFARPTRPROC1DEV2:INAL,STAT2TESTAL,20HJZDEV3CALLFARPTRPROC2DEV3:INAL,STAT3TESTAL,20HJZNO_INPUTCALLFARPTRPROC3NO_INPUT:…8.3中断传送方式非屏蔽中断请求中断逻辑INTn指令INTO指令除法错误单步TF=108090A0B0F0E0D0CIR0IR1IR2IR3IR4IR5IR6IR7系统定时器键盘彩色图形接口串行通信接口2串行通信接口1LPT2控制器磁盘控制器LPT1控制器8259A图8.380X86中断源一、8086的中断分类1.软件中断(1)中断指令INT引起的内中断INT20H(2)处理CPU某些错误的中断除法错中断溢出中断INTO(3)为调试程序(DEBUG)设置的中断2.硬件中断(1)非屏蔽中断(2)来自各种外部设备的中断只允许键盘中断,可设置如下中断屏蔽字MOVAL,11111101BOUT21H,AL系统重新增设键盘中断,指令如下:INAL,21HANDAL,11111101BOUT21H,AL设置和清除IF位STICLI打印机软盘硬盘串行通信口一串行通信口二保留键盘定时器(a)中断屏蔽寄存器(I/O端口21H)RSLEOI00L2L1L0(a)中断命令寄存器(I/O端口20H)结束硬件中断的指令:MOVAL,20HOUT20HAL二、中断向量表中断操作的五个步骤类型0中断向量类型1中断向量类型3CH中断向量602000A0类型3FH中断向量……INT3DHMOVCX,300:00000:00040:00F00:00F40:00F8向量地址=3DH*4=0F4H2060A000STIPUSHDSIRET中断处理程序A000:2060…表8.2中断向量表地址分配地址中断型号地址中断类型号0~7F0~1FBIOS中断向量80~FF20~3FDOS中断向100~17F40~5F扩充BIOS中断向量180~19F60~67用户中断向量1A0~1BF68~6F保留1C0~1DF70~77I/O设备中断向量1E0~1FF78~7F保留200~3C380~FDBASIC3C4~3FFF1~FF保留…0:N*4INHAND:IRET…MOVAX,0MOVES,AXMOVBX,N*4MOVAX,OFFSETINTHANDMOVES:WORDPTR[BX],AXMOVAX,SEGINTHANDMOVES:WORDPTR[BX+2],AX……中断向量表使用DOS功能调用(21H)存取中断向量的方法:设置中断向量把由AL指定的中断类型的中断向量DS:DX放在中断向量表中.预置:AH=25HAL=中断向量号执行:INT21H取中断向量把由AL指定的中断类型的中断向量从中断向量表中取到ES:BX中.预置:AH=35HAL=中断向量号执行:INT21H返回时送:ES:BX=中断向量例8.4使用DOS功能调用存取中断向量.INTHAND:…IRETMOVAL,NMOVAH,35HINT21HPUSHESPUSHBXPUSHDSMOVAX,SEGINTHANDMOVDS,AXMOVDX,OFFSETINTHANDMOVAL,NMOVAH,25HINT21HPOPDS…POPDXPOPDSMOVAL,NMOVAH,25HINT21HRET…三、中断过程当中断发生时,由中断机构自动完成下列动作:(1)取中断类型号N(2)标志寄存器内容(FLAGS)入栈(3)当前代码段寄存器(CS)内容入栈(4)当前指令计数器(IP)内容入栈(5)禁止硬件中断和单步中断(IF=0,TF=0)(6)从中断向量表中取4*N的字的内容送IP,取4*N+2中的字内容送CS(7)转中断处理程序………INTHAND:………IRET产生中断1.FLAGS,CS和IP入栈2.清除IF,TF3.转中断处理程序INTHAND中断返回1.IP,CS和FLAGS出栈2.返回断点,继续执行下一条指令INT12H四、中断优先级和中断嵌套8086规定的优先级次序为:软件中断(除法错,溢出,中断指令)非屏蔽中断(NMI)可屏蔽中断(INTR)单步中断高低………..主程序......IR2处理程序.…IR1处理程序...IR4处理程序......IR3处理程序IR2和IR4中断请求STI(EOI)IRETIR3中断请求STI(EOI)IRET(EOI)IRETSTISTI(EOI)IRET开中断IR1中断清除IR2中断清除正常优先级方式下的典型中断序列IR1中断请求五、中断处理程序主程序（1）设置中断向量（2）设置设备的中断屏蔽位（3）设置CPU的中断允许IF位（开中断)硬件（4）外设接口送中断请求给CPU（5）当前指令执行完后,CPU送响应信号给外设接口(6)CPU接收中断类型号(7)当前的FLAGS,CS和IP保存入栈(8)清除IF和TF(9)中断向量送IP和CS例8.5编写一个中断处理程序,要求在主程序运行过程中,每隔10秒钟响铃一次,同时在屏幕上显示出信息“Thebellisring”.MODELSMALL.STACK.DATACOUNTDW1MSGDB‘Thebellisringing!’,0dh,0ah,’$’.CODEMAINPROCFARSTART:MOVAX,@DATAMOVDS,AXMOVAL,1CHMOVAH,35HINT21HPUSHESPUSHBXPUSHDSMOVAX,SEGRINGMOVDS,AXMOVDX,OFFSETRINGMOVAL,1CHMOVAH,25HINT21HPOPDSINAL,21HANDAL,11111110BOUT21H,ALSTIMOVDI,20000DELAY:MOVSI,30000DELAY1:DECSIJNZDELAY1DECDIJNZDELAYRINGPROCNEARPUSHDSPUSHAXPUSHCXPUSHDXMOVAX,@DATAMOVDS,AXSTIDECCOUNTJNZEXITMOVDX,OFFSETMSGMOVAH,09HINT21HMOVDX,100INAL,61HANDAL,0FCHSOUND:XORAL,02OUT61H,ALMOVCX,1400HWAIT1:LOOPWAIT1DECDXJNESOUNDMOVCOUNT,182EXIT:CLIPOPDXPOPCXPOPAXPOPDSRINGENDPENDSTART例8.6在配置了键盘输入(中断类型09)和打印机输出(中断类型0FH)两种外部设备的80X86中断系统中,要求从键盘上接收字符,同时对32字节的输入缓冲区进行测试,如果缓冲区已满,则键盘挂起,(禁止键盘中断输入),有打印机输出一个提示信息..MODELSMALL.STACK.DATAOLD_IP09DW?OLD_CS09DW?OLD_IP0FDW?OLD_CS0FDW?COUNTDW?BUFFERDB20HDUP(‘’)BUF_PDW?START_MSGDB0ah,0dh,’RUN’,0ah,0dh,’$’END_MSGDB0ah,0dh,’END’,0AH,0DH,’$’FULL_MSGDB’Bufferfull’,0AH,0DH,’$’MAINPROCFARSTART:MOVAX,@DATAMOVDS,AX.CODELEAAX,BUFFERMOVBUF_P,AXMOVCOUNT,0MOVAL,09HMOVAH,35HINT21HMOVOLD_CS09,ESMOVOLD_IP09,BXPUSHDSLEADX,KBDINTMOVAX,SEGKBDINTMOVDS,AXMOVAL,09HMOVAH,25HINT21HPOPDSINAL,21HANDAL,0FDHOUT21H,ALMOVAL,0FHMOVAH,35HINT21HMOVOLD_CS0F,ESMOVOLD_IP0F,BXPUSHDSLEADX,PRTINTMOVAX,SEGPRTINTMOVDS,AXMOVAL,0FHMOVAH,25HINT21HPOPDSLEADX,START_MSGMOVAH,09HINT21HSTIMOVDI,20000MAINP:MOVSI,30000MAINP1:DECSIJNZMAINP1DECDIJNZMAINPLEADX,END_MSGMOVAH,09HINT21HMOVDX,OLD_IP09MOVAX,OLD_CS09MOVDS,AXMOVAL,09HMOVAH,25HINT21HPOPDSCLIPUSHDSMOVDX,OLD_IP0FMOVAX,OLD_CS0FMOVDS,AXMOVAL,0FHMOVAH,25HINT21HPOPDSPUSHDSINAL,21HANDAL,0FDHOUT21H,ALSTIMOVAX,4C00HINT21HMAINENDPKDBINTPROCNEARPUSHAXPUSHBXCLDINAL,60HPUSHAXINAL,61HMOVAH,ALORAL,80HOUT61H,ALXCHGAH,ALOUT61H,ALPOPAXTESTAL,80HJNZRETURN1MOVBX,BUF_FMOV[BX],ALCALLDISPLAY_HEXINCBXINCCOUNTMOVBUF_P,BXCHECK:CMPCOUNT,20HJBRETURN1INAL,21HORAL,2ANDAL,7FHOUT21H,ALCALLINIT_PRTRETURN1:CLIMOVAL,20HOUT20H,ALIRETKBDINTENDPPRTINTPROCNEARPUSHAXPUSHBXPUSHDXMOVBX,BUF_PMOVAL,[BX]MOVDX,378HOUTDX,ALPUSHAXMOVAL,1DHMOVDX,37AHOUTDX,ALJMP$+2MOVAL,1CHOUTDX,ALPOPAXINCBXMOVBUF_P,BXCMPAL,0AHJNZRETURN2INAL,21HORAL,80HOUT21H,ALRETURN2:MOVAL,20HOUT20H,ALPOPDXPOPBXPOPAXIRETPRTINTENDPINIT_PRTPROCNEARPUSHAXPUSHBXPUSHDXCLILEABX,FULL_MSGMOVBUF_P,BXMOVAL,0DHMOVDX,378HOUTDX,ALMOVAL,1DHMOVDX,37AHOUTDX,ALJMP$+2MOVAL,1CHOUTDX,ALPOPDXPOPBXPOPAXIRETINIT_PRTENDPDISPLAY_HEXPROCNEARPUSHAXPUSHCXPUSHDXMOVCH,2MOVCL,4NEXTB:ROLAL,CLPUSHAXMOVDL,ALANDDL,0FHORDL,30HCMPDL,3AHJLDISPITADDDL,7DISPIT:MOVAH,2INT21HPOPAXDECCHJNZNEXTBMOVAH,2MOVDL,‘.’INT21HPOPDXPOPBXPOPAXIRETDISPLAY_HEXENDPENDSTART例8.7除数为0时的软件中断.MODELSMALL.STACK.CODEMAINPROCNEARMOVAX,SEGZDIVMOVDS,AXMOVDX,OFFSETZDIVMOVAL,0MOVAH,25HINT21HMOVAX,@CODEMOVDS,AXMOVDX,OK_MSGMOVAH,9