【正文】 s largest puter. Modern human life used in almost every piece of electronic and machinery products will have singlechip integration. Cell phone, telephone, calculator, home appliances, electronic toys, handheld puter and the puter mouse and other fittings are equipped with the Ministry of Singlechip 12. Personal puter will also have a large number of singlechip microputer at work. General Motors on the Ministry of singlechip microputer is equipped with more than 40 plex industrial control systems there is probably even hundreds of singlechip at the same time job! SCM is not only far exceeds the number of PC and other puting General, even more so than human beings than quantity.Introduce SinglechipSinglechip, also known as singlechip microcontroller, it is not pleted by a certain logic function of the chip, but put into a puter system on a chip. General stresses: a chip bees a puter. Its small size, light weight, cheap, for the study, application and development of facilities provided. At the same time, are studying the use of singlechip puter know the principle and structure of the best selection. Singlechip and puter also with similar functional modules, such as CPU, memory, parallel bus, and hard disk have the same effect as the memory difference is that its performance of these ponents are relatively weak . home puter much, but The prices and fees are low, there is generally no more than 10 yuan you can do with it some control for a class of electrical work is not very plex is sufficient. We are now using fully automatic drum washing machines, smoke hood, VCD and so on inside the home appliances can see its shadow! It is mainly as a control are part of the core ponents.It is an online realtime control puter, is the sceneline control is required there is a strong antiinterference ability, low cost, which is and offline puter (such as home PC) The main difference. Singlechip are relying on the procedure, and can be amended. Through different procedures achieve different functions, in particular, are special and unique features, which other devices are required fee in order to do a great effort, while some are also very difficult to make great efforts to do so. Is not a very plicated function of the United States if the 5039。s 8031, because the performance of a good reliable and easy access to great acclaim. Later on in 8031 developed a series of singlechip microputer system MCS51. Based on singlechip microputer system of the system is still widely used until now. As the field of industrial control requirements improve, beginning a 16bit singlechip, but not ideal because costeffective has not been very widely used. After the 9039。整個(gè)設(shè)計(jì)過(guò)程中，系里領(lǐng)導(dǎo)給予了很大的支持和關(guān)懷，也受到了實(shí)驗(yàn)室老師的照顧，為我們提供了很好的實(shí)驗(yàn)環(huán)境和足夠的實(shí)驗(yàn)時(shí)間，在此表示深深的感謝。而且數(shù)據(jù)的準(zhǔn)確性、實(shí)時(shí)性也得到了保證，整個(gè)成品操作簡(jiǎn)單、維護(hù)方便，為溫度的測(cè)量提供了保證。但要想在實(shí)際應(yīng)用中達(dá)到剛好的使用效果，還需要做大量的改動(dòng)，增加很多功能。 ④在DS1820測(cè)溫程序設(shè)計(jì)中，向DS1820發(fā)出溫度轉(zhuǎn)換命令后，程序總要等待DS1820的返回信號(hào)，一旦某個(gè)DS1820接觸不好或斷線，當(dāng)程序讀該DS1820時(shí)，將沒有返回信號(hào)，程序進(jìn)入死循環(huán)。試驗(yàn)中，當(dāng)采用普通信號(hào)電纜傳輸長(zhǎng)度超過(guò)50m時(shí)，讀取的測(cè)溫?cái)?shù)據(jù)將發(fā)生錯(cuò)誤。在使用PL/M、C等高級(jí)語(yǔ)言進(jìn)行系統(tǒng)程序設(shè)計(jì)時(shí)，對(duì)DS1820操作部分最好采用匯編語(yǔ)言實(shí)現(xiàn)。由于DS18B20與微處理器間采用串行數(shù)據(jù)傳送方式，因此，在對(duì)DS18B20進(jìn)行讀寫編程時(shí)，必須嚴(yán)格地保證讀寫時(shí)序，否則，將無(wú)法正確讀取測(cè)溫結(jié)果。主機(jī)控制DS18B20完成溫度轉(zhuǎn)換時(shí)，在每一次讀寫之前，都要對(duì)DS18B20進(jìn)行復(fù)位，而且該復(fù)位要求主CPU要將數(shù)據(jù)線下拉500μs，然后釋放。硬件調(diào)試比較容易，首先檢查電路的焊接是否正確，然后可用萬(wàn)用表或通電檢測(cè)。 液晶顯示流程初始化退出返回清除顯示屏設(shè)置輸入模式延時(shí)5ms開顯示，無(wú)光標(biāo)延時(shí)5ms功能設(shè)置162顯示、57點(diǎn)陣八位數(shù)據(jù)、不忙檢測(cè)，執(zhí)行三次延時(shí)5ms延時(shí)5ms圖45 液晶顯示器的程序流程圖 1602LCD的一般初始化（復(fù)位）過(guò)程下面我們對(duì)上面的流程圖進(jìn)行語(yǔ)言描述如下：初始化程序延時(shí)15mS寫指令38H（不檢測(cè)忙信號(hào)）延時(shí)5mS寫指令38H（不檢測(cè)忙信號(hào)）延時(shí)5mS寫指令38H（不檢測(cè)忙信號(hào)）以后每次寫指令、讀/寫數(shù)據(jù)操作均需要檢測(cè)忙信號(hào)寫指令38H：顯示模式設(shè)置寫指令08H：顯示關(guān)閉寫指令01H：顯示清屏寫指令06H：顯示光標(biāo)移動(dòng)設(shè)置寫指令0CH：顯示開及光標(biāo)設(shè)置 液晶顯示器的軟件代碼下面我們就軟件的代碼列寫如下，并進(jìn)行了大部分的解釋。在采用12位轉(zhuǎn)換精度時(shí)，就是實(shí)際的十進(jìn)制溫度值。WR1820: CLR C ；發(fā)送1個(gè)字節(jié) MOV R1,8WR18201:CLR DQ ；產(chǎn)生寫信號(hào) LCALL DELAY15 ；延時(shí)17微秒 RRC A MOV DQ,C ；發(fā)送一位數(shù)據(jù)給DS18B20 LCALL DELAY15 ；延時(shí)17微秒 SETB DQ NOP DJNZ R2,WR18201 ；判斷字節(jié)是否發(fā)送發(fā)DS18B20復(fù)位程序發(fā)跳過(guò)ROM發(fā)溫度開始轉(zhuǎn)換命令結(jié)束 SETB DQ RET圖43 溫度轉(zhuǎn)換命令子程序流程圖 計(jì)算溫度子程序計(jì)算溫度子程序?qū)AM中讀取值進(jìn)行BCD碼的轉(zhuǎn)換運(yùn)算，并進(jìn)行溫度值正負(fù)的判定，其程序流程圖如圖11所示。寫時(shí)隙起始于單片機(jī)拉低總線。讀時(shí)隙起始于單片機(jī)拉低總線至少1μs。由于DS18B20通過(guò)單總線與單片機(jī)進(jìn)行通訊，所以其通訊功能是分時(shí)完成的。DS18B20在接受到復(fù)位脈沖后等待15～60μs才發(fā)出應(yīng)答脈沖。具體是由主機(jī)先給DS18B20發(fā)一個(gè)復(fù)位脈沖，在DS18B20發(fā)回響應(yīng)脈沖給主機(jī)后，主機(jī)再發(fā)讀ROM命令(代碼33H)，并發(fā)一個(gè)15μs左右的脈沖，接著再讀取DS18B20序列號(hào)的一位，并用同樣方法讀取序列號(hào)的每一位)。每一步操作必須嚴(yán)格按照時(shí)序規(guī)定進(jìn)行。圖35 系統(tǒng)總的接線圖第4章 軟件設(shè)計(jì)及調(diào)試本系統(tǒng)程序采用模塊化設(shè)計(jì)，主要包括：主程序、讀出溫度子程序、溫度轉(zhuǎn)換命令子程序、計(jì)算溫度子程序、顯示數(shù)據(jù)刷新子程序和延時(shí)程序等。溫度傳感器DS18B20的DQ端實(shí)現(xiàn)與AT89C2051通信，而AT89C51的P0口接液晶顯示器1602對(duì)其進(jìn)行數(shù)據(jù)傳輸。VCC端口接抓換來(lái)的電源。PQ05RF11是+5V穩(wěn)壓集成電路，為4腳直插式塑料封裝。復(fù)位后P0－P3口均置1引腳表現(xiàn)為高電平，程序計(jì)數(shù)器和特殊功能寄存器SFR全部清零。~12MHz ，典型值取12 MHz。時(shí)鐘電路產(chǎn)生的振蕩脈沖經(jīng)過(guò)二分頻以后，才成為單片機(jī)的時(shí)鐘信號(hào)。XTAL1和XTAL2分別為反向放大器的輸入和輸出。②晶振、復(fù)位電路 MCS—51系列單片機(jī)的時(shí)鐘電路是產(chǎn)生單片機(jī)工作所需要的時(shí)鐘信號(hào)，而時(shí)序是指令執(zhí)行中各信號(hào)之間在時(shí)間上的相互關(guān)系。液晶顯示：LCD有明顯的優(yōu)點(diǎn)：微功耗、尺寸小、超薄輕巧、顯示信息量大、字跡清晰、美觀、視覺舒適；適于用LCD液晶顯示器顯示中文菜單。另一種是寄生電源供電方式，如圖35單片機(jī)端口接單線總線，為保證在有效的DS18B20時(shí)鐘周期內(nèi)提供足夠的電源，可用一個(gè)MOSFET管來(lái)完成對(duì)總線的上拉。表210 字符代碼與圖形對(duì)應(yīng)圖高位低位0000001001000101011001111010101111001101111011110000(1)0aP\pスつαβ0001(2)!1AQaqァコаκγ0010(3)2BRbrィヶмλδ0011(4)3CScsサクуμε0100(5)$4DTdtナォйνζ0101(6)%5EUeuマゥжξη0110(7)amp。要顯示字符時(shí)要先輸入顯示字符地址，也就是告訴模塊在哪里顯示字符，圖25是1602的內(nèi)部顯示地址。 指令9：讀忙信號(hào)和光標(biāo)地址 BF：為忙標(biāo)志位，高電平表示忙，此時(shí)模塊不能接收命令或者數(shù)據(jù)，如果為低電平表示不忙。 指令5：光標(biāo)或顯示移位 S/C：高電平時(shí)移動(dòng)顯示的文字，低電平時(shí)移動(dòng)光標(biāo)。指令3：光標(biāo)和顯示模式設(shè)置 I/D：標(biāo)移動(dòng)方向，高電平右移，低電平左移 S：屏幕上所有文字是否左移或者右移。第16腳：背光源負(fù)極。當(dāng)RS和R/W共同為低電平時(shí)可以寫入指令或者顯示地址，當(dāng)RS為低電平R/W為高電平時(shí)可以讀忙信號(hào)，當(dāng)RS為高電平R/W為低電平時(shí)可以寫入數(shù)據(jù)。第2腳：VDD接5V正電源。 液晶顯示的工作原理[8](1)1602LCD的基本參數(shù)及引腳功能1602LCD分為帶背光和不帶背光兩種，控制器大部分為HD44780，帶背光的比不帶背光的厚，是否帶背光在應(yīng)用中并無(wú)差別。字符的顯示：用LCD顯示一個(gè)字符時(shí)比較復(fù)雜，因?yàn)橐粋€(gè)字符由68或88點(diǎn)陣組成，既要找到和顯示屏幕上某幾個(gè)位置對(duì)應(yīng)的顯示RAM區(qū)的8字節(jié)，還要使每字節(jié)的不同位為“1”，其它的為“0”，為“1”的點(diǎn)亮，為“0”的不亮。如果根據(jù)驅(qū)動(dòng)方式來(lái)分，可以分為靜態(tài)驅(qū)動(dòng)（Static）、單純矩陣驅(qū)動(dòng)（Simple Matrix）和主動(dòng)矩陣驅(qū)動(dòng)（Active Matrix）三種。③體積小、重量輕液晶顯示器通過(guò)顯示屏上的電極控制液晶分子狀態(tài)來(lái)達(dá)到顯示的目的，在重量上比相同顯示面積的傳統(tǒng)顯示器要輕得多。相對(duì)而言，液晶顯示器具有厚度薄、適用于大規(guī)模集成電路直接驅(qū)動(dòng)、易于實(shí)現(xiàn)全彩色顯示的特點(diǎn)，被廣泛應(yīng)用在便攜式電腦、數(shù)字?jǐn)z像機(jī)、PDA移