电子万年历设计与制作

-4推算阴历日期的程序流程图5测试结果设计完成后，给系统上电，液晶显示屏显示结果如图5-1所示。滚动显示天津工程师范学院自动化0302班许宁毕业设计SOLAR2000/01/01LUNAR2095/11/25滚动显示天津工程师范学院自动化0302班许宁毕业设计SOLAR2000/01/01LUNAR2095/11/2500:00:00SUN闹铃关闰月00:00滚动显示图5-1液晶显示屏的显示结果调节10K电位器R4可调整液晶显示屏的亮度。调整到合适亮度后，按控制按钮，光标会从阳历年位开始闪烁，进入设定调整状态。此时按加按钮，当前数字就可改变。按一次，数字加1；若长按，则数字连续加。此时，调整的位一直在闪烁，直到再次按光标移动控制位，光标跳到下一位闪烁。调整顺序依次为：阳历年、月、日，阴历年、月、日，时、分、秒，闹铃时、分。当全部参数调整完毕后，按退出按钮，光标停止闪烁，退出设定调整状态；当再次按下此按钮，闹铃显示“开”；当第三次按下此键，闹铃显示“关”。若当前月为闰月，则屏幕左下角会显示“闰月”；若不是闰月，则无显示。调试分为硬件调试和软件调试。硬件调试主要是检测硬件电路是否有短路、断路、虚焊等。DS1302的硬件电路很简单，只通过3根线与单片机相连，很容易检测，主要是检查其引脚，如晶振和电源等是否接好。另外可以通过软件来调试硬件，如为了测试显示电路连接是否正确，可以编写一个简单的显示程序来测试它。接下来可进行软件调试，可以编写只含DS1302的计时和读写程序、显示程序，测试DS1302是否正常工作。最后调试时间调整程序和阴历推算程序。计时器最关键的是计时的精度。电子万年历中DS1302电路使用专用的晶振，经测试制作的电子万年历，一星期快了3s左右，误差较大，实验设计中可换用标准晶振或用软件进行修正。6结论本设计硬件电路的使用比较简单，所用元器件较少，电路中使用了AT89S52单片机、DS1302时钟芯片、24C02FLASH存储器和HY-12864液晶显示器等主要芯片,实现了预计的功能。在对芯片的管脚功能和用法有了充分的了解后，根据原先的选择好的设计要求设计硬件电路，包括单片机控制电路、时钟电路、存储电路、键盘接口电路、显示电路和闹铃电路。然后通过软件编程，实现了对年、月、日、时、分、秒、星期、闰年和阴历的自动调整，用按键进行控制，用液晶模块进行显示，并具有闹铃功能。电子万年历可以正常显示时间并进行时间调整，基本完成了预期要实现的目标。但是本设计中还有许多不尽如人意的地方，比如说电路板设计不太合理，体积过大，不便于摆放，阴历查询日期从2000年至2050年，时间过于局限等等。希望老师多多指点和帮助。参考文献[1]吴金戌，沈庆阳．8051单片机实践与应用，北京：清华大学出版社，2003.12，26－38．[2]何立民．单片机应用文集，北京：北京航空航天大学出版社，1991，53－72．[3]公茂法．单片机人机接口实例集，北京：北京航空航天大学出版社，1998.2，32－59．[4]何立明．单片机高级教程——应用与设计，北京：北京航天航空大学出版社，2000.4，149－173．[5]李广弟，朱月秀．单片机基础，北京：北京航空航天大学出版社，2001.8，36－85．[6]楼然苗，李光飞．MCS－51系列单片机设计实例，北京：北京航天航空大学出版社，2001.3，75－83．[7]李华．单片机原理与接口技术，北京：清华大学出版社，33－80．[8]王伟．高性能、低功耗带RAM实时时钟芯片DS1302（上），电子世界：第一期,1995，26－35．[9]王伟．高性能、低功耗带RAM实时时钟芯片DS1302（下），电子世界：第四期，1995，32－41．[10]刘光潭．中外集成电路简明速察手册，上海：电子工业出版社，1991．[11]一九九九年产品目录（第一期），武汉力源股份有限公司，1999．[12]刘利．液晶显示原理，上海：电子工业出版社，2002.5，52－70．[13]李宏，张家田．液晶显示器件应用技术，北京：机械工业出版社，2004，156－183．[14]沈庆阳．汉字显示应用技术，上海：电子工业出版社，2002.3，128－139．[15]MAXIM．NEWRELEASESDATABOOK（VOLUMEV），AMERICA，1996．附录1：电子万年历设计电路原理图附录2：主程序MAIN:MOVSP,#70HLCALLDELAY;LCALLDELAY;LCALLDELAYMOV59H,#00H;判断调整地址CLR22H;停止周期第三位闪烁CLR23H;判断是否开闹铃CLRP3.5MOVIE,#00H;关所有中断MOVTMOD,#10HMOVTL1,#0F0HMOVTH1,#00H;MOVIP,#01H;SETBEX0 ;开外中断SETBEA ;开总中断允许LCALLVIICREAD;将EEPROM中原频率数据调入内存;MOV65H,#00H;MOV66H,#00H;MOV67H,#00H;MOV68H,#00HLCALLINTLCALLCLEARLCALLINTSHILCALLDDD;静态字显示DONGXIAN:MOVDPTR,#CCTAB;以下字为动态显示MOVZIDI,DPLMOVZIGAO,DPHMOVDONGXH,#1CHDXH1:MOVPAGER,#00H;16X16点阵字体,第2页MOVCOLUMN,#00H;起始列为第0列MOVCODER,#00H;字符代码LCALLCCW_PRMOVPAGER,#00HMOVCOLUMN,#10HMOVCODER,#01HLCALLCCW_PRMOVPAGER,#00HMOVCOLUMN,#20HMOVCODER,#02HLCALLCCW_PRMOVPAGER,#00H;16X16点阵字体,第2页MOVCOLUMN,#30H;起始列为第0列MOVCODER,#03H;字符代码LCALLCCW_PRMOVPAGER,#00HMOVCOLUMN,#40HMOVCODER,#04HLCALLCCW_PRMOVPAGER,#00HMOVCOLUMN,#50HMOVCODER,#05HLCALLCCW_PRMOVPAGER,#00HMOVCOLUMN,#60HMOVCODER,#06HLCALLCCW_PRMOVPAGER,#00HMOVCOLUMN,#70HMOVCODER,#07HLCALLCCW_PRLCALLDELAYCLRC;动态显示循环程序控制MOVA,ZIDIADDA,#20HMOVZIDI,AMOVA,ZIGAOADDCA,#00HMOVZIGAO,AL1:MOV3CH,#0F7H;开始键扫描MOV3DH,#00HL2:MOVA,3CHMOVP2,AMOVA,P2MOV3EH,ASETBCMOV3FH,#04HL3:RLCAJNCMNJIXUINC3DHDJNZ3FH,L3LCALLDISP1MOVA,3CHSETBCRRCAMOV3CH,AJCL2JMPMNMNMNJIXU:MOVA,P2XRLA,3EHJNZDF3AJMPDF3;MNJIXUDF3:CLRCMOVA,3DHRLCAMOVDPTR,#TABLEJMP@A+DPTRAJMPDONGXIANTABLE:AJMPMN0;键盘入口地址AJMPMN1AJMPMN2AJMPMN3AJMPMN4AJMPMN5AJMPMN6AJMPMN7AJMPMN8AJMPMN9AJMPMN10AJMPMN11AJMPMN12AJMPMN13AJMPMN14AJMPMN15MNFH:AJMPDXH1MNMN:DJNZDONGXH,MNFHAJMPDONGXIAN;键盘入口地址MN0:CLREAMOVBAOHUDI2,ZIDIMOVBAOHUGAO2,ZIGAOMOVCDAT1,#10001110B;打开写保护MOVCDAT2,#00000000BLCALLDSWORD;判断调整的地址SETBTR1SETBET1MOVA,59HCJNEA,#00H,JIANPAN1MOV5AH,#8CHINC59H;年时间MOVYJSSDZ0,#82HMOVYJSSDZ1,#40HMOVYJSSDZ2,#82HMOVYJSSDZ3,#48HLJMPJIAN1_0JIANPAN1:MOVA,59HCJNEA,#01H,JIANPAN2MOV5AH,#88HINC59H;月时间MOVYJSSDZ0,#82HMOVYJSSDZ1,#58HMOVYJSSDZ2,#82HMOVYJSSDZ3,#60HLJMPJIAN1_0JIANPAN2:MOVA,59HCJNEA,#02H,JIANPAN3MOV5AH,#86HINC59H;日时间MOVYJSSDZ0,#82HMOVYJSSDZ1,#70HMOVYJSSDZ2,#82HMOVYJSSDZ3,#78HLJMPJIAN1_0JIANPAN3:MOVA,59HCJNEA,#03H,JIANPAN4MOV5AH,#84HINC59H;时时间MOVYJSSDZ0,#84HMOVYJSSDZ1,#10HMOVYJSSDZ2,#84HMOVYJSSDZ3,#18HLJMPJIAN1_0JIANPAN4:MOVA,59HCJNEA,#04H,JIANPAN6MOV5AH,#82HINC59H;分时间MOVYJSSDZ0,#84HMOVYJSSDZ1,#28HMOVYJSSDZ2,#84HMOVYJSSDZ3,#30HLJMPJIAN1_0JIANPAN6:MOVA,59HCJNEA,#05H,JIANPAN7MOV5AH,#8AHINC59H;周期SETB22H;启动周期第三位闪烁MOVYJSSDZ0,#84HMOVYJSSDZ1,#58HMOVYJSSDZ2,#84HMOVYJSSDZ3,#60HMOVYJSSDZ4,#84HMOVYJSSDZ5,#68HLJMPJIAN1_0JIANPAN7:MOVA,59HCJNEA,#06H,JIANPAN8MOV5AH,#01H;判断是否能执行键2键3INC59H;时闹铃MOVYJSSDZ0,#87HMOVYJSSDZ1,#30HMOVYJSSDZ2,#87HMOVYJSSDZ3,#38HCLR22H;停止周期第三位闪烁LJMPJIAN1_0JIANPAN8:MOVA,59HCJNEA,#07H,JIANPAN9INC59H;分闹铃MOVYJSSDZ0,#87HMOVYJSSDZ1,#48HMOVYJSSDZ2,#87HMOVYJSSDZ3,#50HCLR22H;停止周期第三位闪烁LJMPJIAN1_0JIANPAN9:MOV59H,#01H;年时间MOV5AH,#8CHMOVYJSSDZ0,#82HMOVYJSSDZ1,#40HMOVYJSSDZ2,#82HMOVYJSSDZ3,#48HJIAN1_0:LCALLDSWRPRT;写保护MOVZIDI,BAOHUDI2MOVZIGAO,BAOHUGAO2;LCALLVIICWRITE;频率数据存入EEPROMSETBEAAJMPMNMNMN1:CLREAMOVBAOHUDI2,ZIDIMOVBAOHUGAO2,ZIGAOMOVA,5AH;看是否进入调整状态CJNEA,#00H,JIAN1_1LJMPJIAN1_11JIAN1_1:MOVA,59HCJNEA,#01H,JIAN1_2MOVCDAT1,#10001110B;打开写保护MOVCDAT2,#00000000BLCALLDSWORDMOVCDAT1,#8Dh;读年LCALLDSRORD;MOVA,CDAT2LCALLADD1MOVCDAT2,ACJNEA,#51H,NIAN1_01MOVCDAT2,#01HNIAN1_01:MOVCDAT1,#8CHLCALLDSWORD;写年LCALLDSWRPRT;写保护LJMPJIAN1_11JIAN1_2:MOVA,59HCJNEA,#02H,JIAN1_3MOVCDAT1,#10001110B;打开写保护MOVCDAT2,#00000000BLCALLDSWORDMOVCDAT1,#89h;读月LCALLDSRORD;MOVA,CDAT2LCALLADD1MOVCDAT2,ACJNEA,#13H,NIAN1_02MOVCDAT2,#01HNIAN1_02:MOVCDAT1,#88HLCALLDSWORD;写月LCALLDSWRPRT;写保护LJMPJIAN1_11JIAN1_3:MOVA,59HCJNEA,#03H,JIAN1_4ALJMPNEXXIJIAN1_4A:LJMPJIAN1_4NEXXI:MOVCDAT1,#10001110B;打开写保护MOVCDAT2,#00000000BLCALLDSWORDMOVCDAT1,#87h;读日LCALLDSRORD;MOVA,CDAT2LCALLADD1MOVCDAT2,AMOVR0,CYEAR;判断日期是30还是31还是28还是29LCALLBCD_10MOVA,R0MOVB,#04HDIVABMOVA,BJNZGGG11MOVA,CMONTHCJNEA,#02H,GGG11MOVA,CDAT2CJNEA,#30H,NIAN1_031MOVCDAT2,#01HNIAN1_031:MOVCDAT1,#86HLCALLDSWORD;写日LCALLDSWRPRT;写保护LJMPJIAN1_11GGG11:MOVA,CMONTH;非闰年CJNEA,#01H,NIAN1_033LJMPNIAN1_032NIAN1_033:MOVA,CMONTHCJNEA,#02H,NIAN1_034MOVA,CDAT2CJNEA,#29H,NIAN1_0333MOVCDAT2,#01HNIAN1_0333:MOVCDAT1,#86HLCALLDSWORD;写日LCALLDSWRPRT;写保护LJMPJIAN1_11NIAN1_034:MOVA,CMONTHCJNEA,#03H,NIAN1_035LJMPNIAN1_032NIAN1_035:MOVA,CMONTHCJNEA,#04H,NIAN1_036LJMPNIAN1_0336NIAN1_036:MOVA,CMONTHCJNEA,#05H,NIAN1_037LJMPNIAN1_032NIAN1_037:MOVA,CMONTHCJNEA,#06H,NIAN1_038LJMPNIAN1_0336NIAN1_038:MOVA,CMONTHCJNEA,#07H,NIAN1_039LJMPNIAN1_032NIAN1_039:MOVA,CMONTHCJNEA,#08H,NIAN1_040LJMPNIAN1_032NIAN1_040:MOVA,CMONTHCJNEA,#09H,NIAN1_041LJMPNIAN1_0336NIAN1_041:MOVA,CMONTHCJNEA,#10H,NIAN1_042LJMPNIAN1_032NIAN1_042:MOVA,CMONTHCJNEA,#11H,NIAN1_043LJMPNIAN1_0336NIAN1_043:LJMPNIAN1_032NIAN1_032:MOVA,CDAT2CJNEA,#32H,NIAN1_03MOVCDAT2,#01HNIAN1_03:MOVCDAT1,#86HLCALLDSWORD;写日31LCALLDSWRPRT;写保护LJMPJIAN1_11NIAN1_0336:MOVA,CDAT2CJNEA,#31H,NIAN1_03AMOVCDAT2,#01HNIAN1_03A:MOVCDAT1,#86HLCALLDSWORD;写日30LCALLDSWRPRT;写保护LJMPJIAN1_11JIAN1_4:MOVA,59HCJNEA,#04H,JIAN1_5MOVCDAT1,#10001110B;打开写保护MOVCDAT2,#00000000BLCALLDSWORDMOVCDAT1,#85h;读时LCALLDSRORD;MOVA,CDAT2LCALLADD1MOVCDAT2,ACJNEA,#24H,NIAN1_04MOVCDAT2,#00HNIAN1_04:MOVCDAT1,#84HLCALLDSWORD;写时LCALLDSWRPRT;写保护LJMPJIAN1_11JIAN1_5:MOVA,59HCJNEA,#05H,JIAN1_6MOVCDAT1,#10001110B;打开写保护MOVCDAT2,#00000000BLCALLDSWORDMOVCDAT1,#83h;读分LCALLDSRORD;MOVA,CDAT2LCALLADD1MOVCDAT2,ACJNEA,#60H,NIAN1_05MOVCDAT2,#00HNIAN1_05:MOVCDAT1,#82HLCALLDSWORD;写分LCALLDSWRPRT;写保护LJMPJIAN1_11JIAN1_6:MOVA,59HCJNEA,#06H,JIAN1_7MOVCDAT1,#10001110B;打开写保护MOVCDAT2,#00000000BLCALLDSWORDMOVCDAT1,#8Bh;读星期LCALLDSRORD;MOVA,CDAT2LCALLADD1MOVCDAT2,ACJNEA,#08H,NIAN1_06MOVCDAT2,#01HNIAN1_06:MOVCDAT1,#8AHLCALLDSWORD;写星期LCALLDSWRPRT;写保护LJMPJIAN1_11JIAN1_7:MOVA,59HCJNEA,#07H,JIAN1_8MOVA,65H;写闹时SWAPAORLA,66HADDA,#01HDAAMOV69H,ACJNEA,#24H,JIAN1_71MOV65H,#00HMOV66H,#00HLCALLVIICWRITELJMPJIAN1_11JIAN1_71:MOVA,69HSWAPAANLA,#0FHMOV65H,AMOVA,69HANLA,#0FHMOV66H,ALCALLVIICWRITELJMPJIAN1_11JIAN1_8:MOVA,67H;写闹分SWAPAORLA,68HADDA,#01HDAAMOV69H,ACJNEA,#60H,JIAN1_81MOV67H,#00HMOV68H,#00HLCALLVIICWRITELJMPJIAN1_11JIAN1_81:MOVA,69HSWAPAANLA,#0FHMOV67H,AMOVA,69HANLA,#0FHMOV68H,ALCALLVIICWRITEJIAN1_11:MOVZIDI,BAOHUDI2MOVZIGAO,BAOHUGAO2;LCALLVIICWRITE;频率数据存入EEPROMSETBEAAJMPMNMNMN2:CLREAMOVBAOHUDI2,ZIDIMOVBAOHUGAO2,ZIGAOMOVA,5AH;看是否进入调整状态CJNEA,#00H,JIAN4_1CPL23HJIAN4_1:CLR22H;停止周期第三位闪烁CLRTR1CLRET1MOV59H,#00HMOV5AH,#00HMOVZIDI,BAOHUDI2MOVZIGAO,BAOHUGAO2SETBEAAJMPMNMN致谢首先我要感谢我的指导老师XX老师的大力帮助和支持。无论是在课题立项还是在课题的研究阶段X老师都给了我很大的帮助。在毕业设计的这段时间中，X老师不仅使我在学业上有了很大的提高，而且言传身教，使我学到了作为一名大学生所应具备的那种踏实勤恳、一丝不苟、认真求实的优良品质和学习作风。在我进行课题内容的研究中，从技术上给予了我极大的帮助和支持，而且在论文的最后评阅过程中，也给我提出了非常有价值的意见，使我获益极深。衷心地谢谢您，X老师！此外，我还要感谢X老师给予我的无私的帮助，他在程序编写和调试过程中给予了我莫大的帮助。在此，我真诚地感谢他们。最后，我要感谢我的母校XX学院，在校期间，这里给我留下了美好的回忆。特别是在我即将踏上工作岗位的同时，毕业设计整个过程给了我这样一个锻炼的机会，使我加深了对以前知识的理解和巩固，拓宽了知识面，也提高了我对所学知识的综合应用能力。我要对母校说：母校有我三五载，我爱母校一万年。祝愿母校的将来更加美好！PAGEPAGE17英文原文OverviewThe8051familyofmicrocontrollersisbasedonanarchitecturewhichishighlyoptimizedforembeddedcontrolsystems.ItisusedinawidevarietyofapplicationsfrommilitaryequipmenttoautomobilestothekeyboardonyourPC.SecondonlytotheMotorola68HC11ineightbitprocessorssales,the8051familyofmicrocontrollersisavailableinawidearrayofvariationsfrommanufacturerssuchasIntel,Philips,andSiemens.Thesemanufacturershaveaddednumerousfeaturesandperipheralstothe8051suchasI2Cinterfaces,analogtodigitalconverters,watchdogtimers,andpulsewidthmodulatedoutputs.Variationsofthe8051withclockspeedsupto40MHzandvoltagerequirementsdownto1.5voltsareavailable.Thiswiderangeofpartsbasedononecoremakesthe8051familyanexcellentchoiceasthebasearchitectureforacompany'sentirelineofproductssinceitcanperformmanyfunctionsanddeveloperswillonlyhavetolearnthisoneplatform.Thebasicarchitectureconsistsofthefollowingfeatures:1aneightbitALU232descreteI/Opins(4groupsof8)whichcanbeindividuallyaccessed3two16bittimer/counters4fullduplexUART56interruptsourceswith2prioritylevels6128bytesofonboardRAM7separate64KbyteaddressspacesforDATAandCODEmemoryOne8051processorcycleconsistsoftwelveoscillatorperiods.Eachofthetwelveoscillatorperiodsisusedforaspecialfunctionbythe8051coresuchasopcodefetchesandsamplesoftheinterruptdaisychainforpendinginterrupts.Thetimerequiredforany8051instructioncanbecomputedbydividingtheclockfrequencyby12,invertingthatresultandmultiplyingitbythenumberofprocessorcyclesrequiredbytheinstructioninquestion.Therefore,ifyouhaveasystemwhichisusingan11.059MHzclock,youcancomputethenumberofinstructionspersecondbydividingthisvalueby12.Thisgivesaninstructionfrequencyof921583instructionspersecond.Invertingthiswillprovidetheamountoftimetakenbyeachinstructioncycle(1.085microseconds).MemoryOrganizationThe8051architectureprovidestheuserwiththreephysicallydistinctmemoryspaceswhichcanbeseeninFigureA-1.Eachmemoryspaceconsistsofcontiguousaddressesfrom0tothemaximumsize,inbytes,ofthememoryspace.Addressoverlapsareresolvedbyutilizinginstructionswhichreferspecificallytoagivenaddressspace.Thethreememoryspacesfunctionasdescribedbelow.TheCODESpaceThefirstmemoryspaceistheCODEsegmentinwhichtheexecutableprogramresides.Thissegmentcanbeupto64K(sinceitisaddressedby16addresslines).TheprocessortreatsthissegmentasreadonlyandwillgeneratesignalsappropriatetoaccessamemorydevicesuchasanEPROM.However,thisdoesnotmeanthattheCODEsegmentmustbeimplementedusinganEPROM.ManyembeddedsystemsthesedaysareusingEEPROMwhichallowsthememorytobeoverwritteneitherbythe8051itselforbyanexternaldevice.ThismakesupgradestotheproducteasytodosincenewsoftwarecanbedownloadedintotheEEPROMratherthanhavingtodisassembleitandinstallanewEPROM.Additionally,batterybackedSRAMcanbeusedinplaceofanEPROM.ThismethodoffersthesamecapabilitytouploadnewsoftwaretotheunitasdoesanEEPROM,anddoesnothaveanysortofread/writecyclelimitationssuchasanEEPROMhas.However,whenthebatterysupplyingtheRAMeventuallydies,sodoesthesoftwareinit.UsinganSRAMinplaceofanEPROMindevelopmentsystemsallowsforrapiddownloadingofnewcodeintothetargetsystem.Whenthiscanbedone,ithelpsavoidthecycleofprogramming/testing/erasingwithEPROM,andcanalsohelpavoidhasslesoveranincircuitemulatorwhichisusuallyararecommodity.Inadditiontoexecutablecode,itiscommonpracticewiththe8051tostorefixedlookuptablesintheCODEsegment.Tofacilitatethis,the8051providesinstructionswhichallowrapidaccesstotablesviathedatapointer(DPTR)ortheprogramcounterwithanoffsetintothetableoptionallyprovidedbytheaccumulator.Thismeansthatoftentimes,atable'sbaseaddresscanbeloadedinDPTRandtheelementofthetabletoaccesscanbeheldintheaccumulator.Theadditionisperformedbythe8051duringtheexecutionoftheinstructionwhichcansavemanycyclesdependingonthesituation.Anexampleofthisisshownlaterinthischapterin.TheDATASpaceThesecondmemoryspaceisthe128bytesofinternalRAMonthe8051,orthefirst128bytesofinternalRAMonthe8052.ThissegmentistypicallyreferredtoastheDATAsegment.TheRAMlocationsinthissegmentareaccessedinoneortwocyclesdependingontheinstruction.ThisaccesstimeismuchquickerthanaccesstotheXDATAsegmentbecausememoryisaddresseddirectlyratherthanviaamemorypointersuchasDPTRwhichmustfirstbeinitialized.Therefore,frequentlyusedvariablesandtemporaryscratchvariablesareusuallyassignedtotheDATAsegment.Suchallocationmustbedonewithcare,however,duetothelimitedamountofmemoryinthissegment.VariablesstoredintheDATAsegmentcanalsobeaccessedindirectlyviaR0orR1.Theregisterbeingusedasthememorypointermustcontaintheaddressofthebytetoberetrievedoraltered.Theseinstructionscantakeoneortwoprocessorcyclesdependingonthesource/destinationdatabyte.TheDATAsegmentcontainstwosmallersegmentsofinterest.Thefirstsubsegmentconsistsofthefoursetsofregisterbankswhichcomposethefirst32bytesofRAM.The8051canuseanyofthesefourgroupsofeightbytesasitsdefaultregisterbank.TheselectionofregisterbanksischangeableatanytimeviatheRS1andtheRS0bitsintheProcessorStatusWord(PSW).Thesetwobitscombineintoanumberfrom0to3(withRS1beingthemostsignificantbit)whichindicatestheregisterbanktobeused.Registerbankswitchingallowsnotonlyforquickparameterpassing,butalsoopensthedoorforsimplifyingtaskswitchingonthe8051.Thesecondsub-segmentintheDATAspaceisabitaddressablesegmentinwhicheachbitcanbeindividuallyaccessed.ThissegmentisreferredtoastheBDATAsegment.Thebitaddressablesegmentconsistsof16bytes(128bits)abovethefourregisterbanksinmemory.The8051containsseveralsinglebitinstructionswhichareoftenveryusefulincontrolapplicationsandaidinreplacingexternalcombinatoriallogicwithsoftwareinthe8051thusreducingpartscountonthetargetsystem.Itshouldbenotedthatthese16bytescanalsobeaccessedona"byte-wide"basisjustlikeanyotherbyteintheDATAspace.SpecialFunctionRegistersControlregistersfortheinterruptsystemandtheperipheralsonthe8051arecontainedininternalRAMatlocations80hexandabove.TheseregistersarereferredtoasspecialfunctionRegisters(orSFRforshort).Manyofthemarebitaddressable.ThebitsinthebitaddressableSFRcaneitherbeaccessedbyname,indexorbitaddress.Thus,youcanrefertotheEAbitoftheInterruptEnableSFRasEA,IE.7,or0AFH.TheSFRcontrolthingssuchasthefunctionofthetimer/counters,theUART,andtheinterruptsourcesaswellastheirpriorities.TheseregistersareaccessedbythesamesetofinstructionsasthebytesandbitsintheDATAsegment.AmemorymapoftheSFRSindicatingtheregisterswhicharebitaddressableisshowninTableA-1.TheIDATASpaceCertain8051familymemberssuchasthe8052containanadditional128bytesofinternalRAMwhichresideatRAMlocations80hexandabove.ThissegmentofRAMistypicallyreferredtoastheIDATAsegment.BecausetheIDATAaddressesandtheSFRaddressesoverlap,addressconflictsbetweenIDATARAMandtheSFRsareresolvedbythetypeofmemoryaccessbeingperformed,sincetheIDATAsegmentcanonlybeaccessedviaindirectaddressingmodes.TheXDATASpace.Thefinal8051memoryspaceis64Kinlengthandisaddressedbythesame16addresslinesastheCODEsegment.Thisspaceistypicallyreferredtoastheexternaldatamemoryspace(ortheXDATAsegmentforshort).ThissegmentusuallyconsistsofsomesortofRAM(usuallyanSRAM)andtheI/Odevicesorexternalperipheralstowhichthe8051mustinterfaceviaitsbus.ReadorwriteoperationstothissegmenttakeaminimumoftwoprocessorcyclesandareperformedusingeitherDPTR,R0,orR1.InthecaseofDPTR,itusuallytakestwoprocessorcyclesormoretoloadthedesiredaddressinadditiontothetwocyclesrequiredtoperformthereadorwriteoperation.Similarly,loadingR0orR1willtakeminimumofonecycleinadditiontothetwocyclesimposedbythememoryaccessitself.Therefore,itiseasytoseethatatypicaloperationwiththeXDATAsegmentwill,ingeneral,takeaminimumofthreeprocessorcycles.Becauseofthis,theDATAsegmentisaveryattractiveplacetostoreanyfrequently.usedvariablesItispossibletofillthissegmententirelywith64KofRAMifthe8051doesnotneedtoperformanyI/OwithdevicesinitsbusorifthedesignerwishestocycletheRAMonandoffwhenI/Odevicesarebeingaccessedviathebus.Methodsforperformingthistechniquewillbediscussedinchapterslaterinthisbook.On-BoardTimer/CountersThestandard8051hastwotimer/counters(other8051familymembershavevaryingamounts),eachofwhichisafull16bits.Eachtimer/countercanbefunctionasafreerunningtimer(inwhichcasetheycountprocessorcycles)orcanbeusedtocountfallingedgesonthesignalappliedtotheirrespectiveI/Opin(eitherT0orT1).Whenusedasacounter,theinputsignalmusthaveafrequencyequaltoorlowerthantheinstructioncyclefrequencydividedby2(ie:theoscillatorfrequency/24)sincetheincomingsignalissampledeveryinstructioncycle,andthecounterisincrementedonlywhena1to0transitionisdetected(whichwillrequiretwosamples).Ifdesired,thetimer/counterscanforceasoftwareinterruptwhentheyoverflow.TheTCON(TimerControl)SFRisusedtostartorstopthetimersaswellasholdtheoverflowflagsofthetimers.TheTCONSFRisdetailedbelowinTableA-7.Thetimer/countersarestartedorstoppedbychangingthetimerrunbits(TR0andTR1)inTCON.ThesoftwarecanfreezetheoperationofeithertimeraswellasrestartthetimerssimplybychangingtheTrxbitintheTCONregister.TheTCONregisteralsocontainstheoverflowflagsforthetimers.Whenthetimersoverflow,theysettheirrespectiveflag(TF0orTF1)inthisregister.Whentheprocessordetectsa0to1transitionintheflag,aninterruptoccursifitisenabled.Itshouldbenotedthatthesoftwarecansetorclearthisflagatanytime.Therefore,aninterruptcanbepreventedaswellasforcedbythesoftware.MicrocomputerinterfaceAmicrocomputerinterfaceconvertsinformationbetweentwoforms.Outsidethemicrocomputertheinformationhandledbyanelectronicsystemexistsasaphysicalsignals,butwithintheprogram,itisrepresentednumerically.Thefunctionofanyinterfacecanbebrokendownintoanumberofoperationswhichmodifythedatainsomeway,sothantheprocessofconversionbetweentheexternalandinternalformsiscarriedoutinanumberorsteps.ThiscanbeillustratedbymeansofanexamplesuchasthanorFig18.1,whichshowsaninterfacebetweenamicrocomputerandatransducerproducingacontinuouslyvariableanalogsignal.transducersoftenproduceverysmalloutrequiringamplyfrication,ortheymaygeneratesignals.inaformthatneedstobeconvertedagainbeforebeinghandledbytherestofthesystem.Forexample,manytransducersthesevariableresistancewhichmustbeconvertedtoavoltagebyaspecialcircuit.Thisprocessofconvertingthetransduceroutputintoavoltage4signalwhichcanbeconnectedtotherestofthesystemiscalledsignalconditioning.IntheexampleofFigure18.1,thesigmaconditioningsectiontranslatestherangelfvoltageorcurrentsignalsfromthetransducertoonewhichcanbeconvertedtodigitalforumbyananalog-to-digitalconverter.TransducerADCSignalconditioningTransducerADCSignalconditioningI/OSectionI/OSectionFig10-1outputInterfaceAnalog-to-digital–digitalconverter(ADC)isusedtoconvertacontinuouslyvariablesignaltoacorrespondingdigitalforumwhichcantakeanyoneofafixednumberofpossiblebinaryvalues.Iftheoutputlfthetransducerdoesnotvarycontinuously,noADCisnecessary.Inthiscasethesignalconditioningsectionmustconverttheincomingsignaltoaformwhichcanbeconnecteddirectlytothenextpartoftheinterface,theinput/outputsectionlfthemicrocomputeritself.TheI/Osectionconvertsdigital“on/off”voltagesignalstoaformwhichcanbepresentedtotheprocessorviatheviathesystembuses.Herethestateofeachinputlinewhetheritis“on”or“off”,isindicatedbyacorresponding“1”or“0”.Inthelineinputswhichhavebeenconvertedtodigitalform,thepatternsofonesandzerosintheinternalrepresentationwillformbinarynumberscorrespondingtothequantitybeingconverted.The“raw”numbersfromtheinterfacearelimite