硬件技术7-2概要.ppt

1、1,输入/输出接口,（2）,2,四.可编程通信接口16550/82501.RS-232接口标准,DB-25型连接器外形,3,用于异步通信RS-232C的引脚定义,*RS-232还有DB-9的连接器,4,下面介绍RS-232用于异步通信各信号的作用及对应的引脚功能。,1保护地线（引脚1）2信号地线（引脚7）3请求发送（引脚4）、清除发送（引脚5）4数据设备就绪（引脚6）5数据终端就绪（引脚20）,6载波检测（引脚8）7振铃指示（引脚22）8数据信号速率选择（引脚23）9发送数据引脚（引脚2）10.接收数据（引脚3）,返回本节,RS-232主要功能信号,5,串行通信接口的典型连接,6,串行接口适配

2、器由地址译码器、时钟电路、16550/8250UART、数据缓冲器、发送接收驱动器和RS-232插座等组成。由地址译码器接收系统发出的寻址信息，并使能有关的端口寄存器。串行端口COM1和COM2的地址如表所示。其作用为：,2.串行接口适配器(接口卡),串行通信靠发送器、接收器和线缆三部分来实现的。在程序控制下它主要完成以下任务：（1）数据的串并及并串转换。（2）线路和MODEM的控制及状态检测。（3）信号电平TTL与EIA电平的转换。（4）发送和接收数据。,返回本节,7,串行通信适配器框图,8,Auniversalasynchronousreceiver/transmitter(UART).O

3、perationspeed:0-1.5MBaud(Baudis#ofbitstransmitted/sec,includingstart,stop,dataandparity).Includes:AprogrammableBaudrategenerator.SeparateFIFObuffersforinputandandoutputdata(16byteseach).Asychronousserialdata:Transmittedandreceivedwithoutaclockortimingsignal.Two10-bitframesofasynchronousdata.7-or8-bi

4、tASCII,e.g.worw/oparity,ispossible.,3.可编程通信接口芯片16550/8250功能与引脚(DIP40/PLCC40）,*FIFO-FirstInFirstOut*PLCC-PlasticLead-lessChipCarrier塑料无引线芯片载体,9,Twoseparatesectionsareresponsiblefordatacommunications:ReceiverTransmitterCanfunctionin:simplex:transmitonlyhalf-duplex:transmitandreceivebutnotsimultaneousl

5、yfull-duplex:transmitandreceivesimultaneouslyThe16550cancontrolamodemthroughDSR,DTR,CTS,RTS,RIandDCD.Inthiscontext,themodemiscalledthedatasetwhilethe16550iscalledthedataterminal.,可编程通信接口芯片16550引脚信号,10,16550引脚功能,A0,A1andA2(input):Selectaninternalregisterforprogramminganddatatransfer.,ADS(input):Addre

6、ssstrobeusedtolatchaddressandchipselect.NotneededonIntelsystems-connectedtoground.BAUDOUT(output):ClocksignalfromBaudrategeneratorintransmitter.CS0,CS1,CS2(input):ChipselectsCTS(input):Cleartosend-indicatesthatthemodemordatasetisreadytoexchangeinformation.(Usedinhalf-duplextoturnthelinearound).,11,D

7、7-D0(input/output):Thedatabuspinsareconnectedtothemicroprocessordatabus.DCD(input):Thedatacarrierdetect-usedbythemodemtosignalthe16550thatacarrierispresent.DDIS(output):Disabledriveroutput-setto0toindicatethatthemicroprocessorisreadingdatafromtheUART.Usedtochangedirectionofdataflowthroughabuffer.DSR

8、(input):Datasetreadyisaninputto16550-indicatesthatthemodem(dataset)isreadytooperate.DTR(output):Dataterminalreadyisanoutput-indicatesthatthedataterminal(16550)isreadytofunction.INTR(output):Interruptrequestisanoutputtothemicro-usedtorequestaninterrupt.ReceivererrorDatareceivedTransmitbufferempty,12,

9、MR(input):Masterreset-connecttosystemRESETOUT1,OUT2(output):Userdefinedoutputpinsformodemorotherdevice.RCLK(input):Receiverclock-clockinputtothereceiversectionoftheUART.Always16XthedesiredreceiverBaudrate.RD,RD(input):Readinputs(eithercanbeused)-causedatatobereadfromtheregistergivenbytheaddressinput

10、s.RI(input):Ringindicatorinput-setto0bymodemtoindicatetelephoneisringing.RTS(output):Request-to-send-signaltomodem,indicatingUARTwishestosenddata.SIN(input),SOUT(output):Serialdatapins,inandout.RXRDY(input):Receiverready-usedtotransferreceiveddataviaDMAtechniques.TXRDY(output):Transmitterready-usedt

11、otransfertransmitterdataviaDMA.WR,WR(input):Write(eithercanbeused)-connectstomicrowritesignaltotransfercommandsanddatato16550.XIN,XOUT:Mainclockconnections-acrystaloscillatorcanbeused.,13,16550电路应用连接,与8088微处理器连接，端口地址为00F0H00F7H的16550,14,16550/8250UART内部寄存器框图,4.16550/8250UART内部寄存器,15,中断允许寄存器(A2A1A0=0

12、01),中断标识寄存器(A2A1A0=010),16,FIFO控制寄存器(A2A1A0=010),初始化FIFO的状态,17,线路控制寄存器(A2A1A0=011),设定串行数据格式和波特率,18,线路状态寄存器(A2A1A0=101),发送或接收时查询是否准备就绪，有否错误,19,5.编程与控制5.1初始化-编程线路控制寄存器、波特率发生器和FIFO,Twophases:Initialization,operation.Initialization:AfterRESET,thelinecontrolregisterandbaudrategeneratorneedtobeprogrammed.

13、Linecontrolregistersetsthe#ofdatabits,#ofstopbitsandtheparity.Addressedatlocation011.Stopbits:S=1,1.5stopbitsusedfor5databits,2usedfor6,7or8.,20,Initialization(cont.)ST,PandPEusedtosendevenoroddparity,tosendnoparityortosenda1ora0intheparitybitpositionforalldata.Noparity,both0-usedforinternetconnecti

14、ons.SB=1causesabreaktobetransmittedonSOUT.Abreakisatleasttwoframeof0data.DL=1enablesprogrammingofthebaudratedivisor.,21,Initialization(cont.)Baudrategeneratorisprogrammedwithadivisorthatsetsbaudrateoftransmitter.Baudrategeneratorisprogrammedat000and001.Port000usedtoholdleastsignificantbyte,001mostsi

15、gnificant.Valueuseddependsonexternalclock/crystalfrequency.For18.432MHzcrystal,10,473gives110bandrate,30gives38,400baud.Note,numberprogrammedgeneratesaclock16XthedesiredBaudrate.Last,theFIFOcontrolregistermustbeprogrammedat010.,22,波特率与除数寄存器值的关系,*波特率=晶体频率/(N*除数值)-N取1，16，32等*本例若选取晶体频率为18.432MHZ，N=16，则

16、除数值应乘以10,23,PC系统中串行端口寄存器地址,24,例：一个异步系统需要7位数据位、奇校验、9600的波特率及1位停止位，端口地址为3F8H3FFH（COM1），其初始化程序为LINEEQU3FBH；线路控制寄存器LSBEQU3F8H；波特率除数寄存器低位MSBEQU3F9H；波特率除数寄存器高位FIFOEQU3FAH；FIFO控制寄存器STARTPROCNEARMOVAL，10001010B；允许除数锁存MOVDX，LINE指向除数寄存器OUTDX，AL,25,MOVAL，120；除数值120，波特率9600MOVDX，LSBOUTDX，ALINCDX；指向高位MOVAL，0OUTD

17、X，ALINCDX；指向线路控制寄存器INCDXMOVAL，00001010B；7位数据位OUTDX，AL1位停止位，奇校验无间隔发送,26,MOVAL，00000111B；初始化FIFO，FIFO使能DECDX清除接收器/发送器OUTDX，ALRETSTARTENDP5.2发送串行数据-线路状态寄存器、发送器锁存,27,Operating:Statuslineregistergivesinformationabouterrorconditionsandstateofthetransmitterandreceiver.Thisregisterneedstobetestedinsoftwarer

18、outinesdesignedtousethe16550totransmit/receivedata.SupposeaprogramwantstosenddataoutSOUT.ItneedstopooltheTHbittodetermineiftransmitterisreadytoreceivedata.Toreceiveinformation,theDRbitistested.,28,例：将AH的内容发送给16550并通过其串行数据引脚SOUT输出，其程序为LSTATEQU3FDH；线路状态寄存器DATAEQU3F8H；发送器锁存SENDPROCNEARPUSHAXPUSHDXSEND1

19、：MOVDX，LSTATINAL，DX；读线路状态TESTAL，20H；测试TH位JZSEND1；等待发送器准备就绪,29,MOVAL，AH；取数据SUBDX，5；指向发送器锁存OUTDX，AL；发送数据POPDXPOPAXRETSENDENDP5.3接收串行数据-线路状态寄存器、接收缓冲器,30,Operating:Itisalsoagoodideatocheckforerrors.Parityerror（1）:Receiveddatahaswrongerror-transmissionbitflipduetonoise.Framingerror（1）:Startandstopbitsnotintheirproperplaces.Thisusuallyresultsifthereceiverisreceiving