【正文】 外部拉低的引腳由于內(nèi)部電阻的原因，將輸出電流(TTL)。作為輸出口，每位能驅(qū)動(dòng)8個(gè)TTL邏輯電平。整個(gè)電路都是通過軟件控制實(shí)現(xiàn)設(shè)計(jì)要求。(2) 明確各模塊之間的數(shù)據(jù)流傳遞關(guān)系，力求數(shù)據(jù)傳遞少，以增強(qiáng)各模塊的獨(dú)立性，便于軟件編制和調(diào)試。總體硬件結(jié)構(gòu)框圖如圖11所示。在技術(shù)上，以單片機(jī)控制的單參數(shù)單回路系統(tǒng)居多，尚無真正意義上的多參數(shù)綜合控制系統(tǒng)，與發(fā)達(dá)國家相比，存在較大差距。 國內(nèi)外研究狀況及發(fā)展1. 國外溫度測控系統(tǒng)研究國外對溫度控制技術(shù)研究較早，始于20世紀(jì)70年代。傳統(tǒng)的溫度采集電路相當(dāng)復(fù)雜，需要經(jīng)過溫度采集、信號放大、濾波、AD轉(zhuǎn)換等一系列工作才能得到溫度的數(shù)字量，并且這種方式不僅電路復(fù)雜，元器件個(gè)數(shù)多，而且線性度和準(zhǔn)確度都不理想，抗干擾能力弱。摘 要隨著國民經(jīng)濟(jì)的發(fā)展，單片機(jī)技術(shù)應(yīng)用已經(jīng)成為高、新科學(xué)技術(shù)的重要內(nèi)容和標(biāo)志之一，它在國民經(jīng)濟(jì)的各個(gè)領(lǐng)域正在發(fā)揮著引人注目的作用。以計(jì)算機(jī)為例，當(dāng)中的中央處理器的運(yùn)行速度愈快，所耗散的熱量便愈多，為免計(jì)算機(jī)系統(tǒng)過熱而受損，有關(guān)系統(tǒng)必須加強(qiáng)溫度過高保護(hù)功能。尋求性能可靠、價(jià)格低廉，且應(yīng)用廣泛的元器件是生產(chǎn)過程的首先要考慮的問題，因此設(shè)計(jì)一種控制簡單、精度較高、價(jià)格低廉的控制系統(tǒng)會(huì)有很好的發(fā)展前景。我國溫度測控設(shè)施計(jì)算機(jī)應(yīng)用，在總體上正從消化吸收、簡單應(yīng)用階段向?qū)嵱没⒕C合性應(yīng)用階段過渡和發(fā)展。2. 方案設(shè)計(jì)本系統(tǒng)采用了單片機(jī)AT89S52，利用數(shù)字溫度傳感器DS18B20對環(huán)境進(jìn)行測溫，同時(shí)采用MAX7219驅(qū)動(dòng)六位7段共陰極數(shù)碼管，同時(shí)還采用EEPROM對溫度上下限進(jìn)行存儲(chǔ)，此外還有鍵盤設(shè)備來實(shí)現(xiàn)溫度上下限值的設(shè)置，紅綠燈報(bào)警溫度的越線，繼電器和電機(jī)對溫度進(jìn)行調(diào)整等來實(shí)現(xiàn)該溫度控制器的智能化。本系統(tǒng)的設(shè)計(jì)方案和步驟如下：(1) 根據(jù)需求按照系統(tǒng)的功能要求，逐級劃分模塊。 AT89S52AT89S52是一種低功耗、高性能CMOS8位微控制器，具有8K在系統(tǒng)可編程Flash 存儲(chǔ)器。對P0端口寫 “1”時(shí)，引腳用作高阻抗輸入。此外。RST：復(fù)位輸入。EA/VPP：外部訪問允許，欲使CPU僅訪問外部程序存儲(chǔ)器(地址為0000HFFFFH)，EA端必須保持低電平(接地)。 鍵盤電路鍵盤是單片機(jī)應(yīng)用系統(tǒng)中的主要輸入設(shè)備，單片機(jī)使用的鍵盤分為編碼鍵盤和非編碼鍵盤。第三位數(shù)碼管靜態(tài)顯示符號“℃”。DS1822的精度較差為177。這種設(shè)計(jì)使總線上的器件在合適的時(shí)間驅(qū)動(dòng)它。自動(dòng)截止是為確保：1時(shí)，在總線操作的間隙總線處于空閑狀態(tài)，即高態(tài)。對于DS18B20寫0時(shí)序和寫1時(shí)序的要求不同，當(dāng)要寫0時(shí)序時(shí)，單總線要被拉低至少60us，保證DS18B20能夠在15us到45us之間能夠正確地采樣IO總線上的“0”電平，當(dāng)要寫1時(shí)序時(shí)，單總線被拉低之后，在15us之內(nèi)就得釋放單總線。如圖38所示，通過使用一個(gè) MOSFET 把 DQ 線直接接到電源可實(shí)現(xiàn)這一點(diǎn)，這時(shí)DS18B20 工作在寄生電源工作方式，在該方式下 VDD 引腳必須連接到地。連接DS18B20的總線電纜是有長度限制的。數(shù)據(jù)存儲(chǔ)格式如表32所示。SDA：串行數(shù)據(jù)/地址CAT24WC01/02/04/08/16雙向串行數(shù)據(jù)/地址管腳用于器件所有數(shù)據(jù)的發(fā)送或接收SDA是一個(gè)開漏輸出管腳可與其它開漏輸出或集電極開路輸出進(jìn)行線或wireOR。時(shí)鐘線為高電平時(shí)，數(shù)據(jù)線的任何電平變化將被當(dāng)作總線的啟動(dòng)或停止條件。5. 器件地址的約定：主器件在發(fā)送啟動(dòng)命令后開始傳送，主器件發(fā)送相應(yīng)的從器件的地址(見表33)，8位從器件地址的高4位固定為1010。C時(shí)序，WP引腳接地，如圖315所示。報(bào)警電路原理圖如圖317所示?！馧O：Normal Open常開點(diǎn)。操作協(xié)議為：初始化DS18B20(發(fā)復(fù)位脈沖)→發(fā)ROM功能命令→發(fā)存儲(chǔ)器操作命令→處理數(shù)據(jù)DS18B20雖然具有測溫系統(tǒng)簡單、測溫精度高、連接方便、占用口線少等優(yōu)點(diǎn)， DS18B20必須首先調(diào)用啟動(dòng)溫度轉(zhuǎn)換函數(shù)，根據(jù)數(shù)據(jù)手冊上對應(yīng)轉(zhuǎn)換時(shí)間來超作，如為12位轉(zhuǎn)換，則應(yīng)該是最大750mS，另外在對DS18B20超作時(shí)，時(shí)序要求非常嚴(yán)格，因此最好禁止系統(tǒng)中斷。DS18B20在完成一個(gè)讀時(shí)序過程，至少需要60us才能完成。DS18B20已經(jīng)被檢測到!!!!!!!!!!!!!!!跳過ROM匹配 LCALL WRITE_1820 MOV A,44H 。圖43 鍵盤掃描子程序流程圖 報(bào)警處理流程運(yùn)行程序后，溫度傳感器DS18B20即可對環(huán)境進(jìn)行溫度采集，并送LED數(shù)碼管顯示。如果能注意這些問題，電路基本不會(huì)出錯(cuò)。 數(shù)據(jù)測試1. 靜態(tài)數(shù)據(jù)測試取一桶凈水，改變它的溫度，觀察數(shù)碼管上顯示的溫度值，并用溫度計(jì)進(jìn)行測溫，記錄兩組數(shù)據(jù)，比較差異。同樣在對軟件進(jìn)行設(shè)計(jì)時(shí)，也可為一路坎坷。感謝母校為我們提供的良好學(xué)習(xí)環(huán)境，使我們能夠在此專心學(xué)習(xí)，陶冶情操。最后，我必須感謝我的朋友，正是因?yàn)樗麄冊陔娔X技術(shù)上的無私指引，我才能得以順利完成該論文。[6] ,2007。s largest number of puter. Of modern human life in almost every electronic and mechanical products will be integrated microcontroller. Mobile phone, telephone, calculator, household appliances, electronic toys, handheld puters, as well as mouse and other puter accessories with 12 Ministry microcontroller. The PC will have a large number of microcontroller work. Generally equipped with more than 40 singlechip in the car, even in plex industrial control systems may have hundreds of single chip at the same time! The number of SCM is not only far more than the sum of PC and other puting even more than the number of human beings even more. The singlechip, also known as singlechip microcontroller, it is not the pletion of a logical function of the chip, but a puter system integrated onto one chip. Equivalent to a miniputer and puter, microcontroller only the lack of I / O devices. Speaking in general terms: a chip has bee a puter. Its small size, light weight, inexpensive, and provide favorable conditions for learning, application and development. At the same time, learning to use the microcontroller is the best choice for the understanding of puter theory and structure. Internal microcontroller with a similar module and the puter functions, such as CPU, memory, parallel bus, the same memory and hard disk role, different performance of these ponents are relatively weak a lot of our home puter, but the price is low generally not more than 10 yuan can be use it for control appliances of a class is not very plex work enough. We are using household appliances inside of the drum fully automatic washing machine, exhaust hood, VCD and so on can be seen in its presence, it is mainly as part of the core parts. It is an online realtime control puter, online site control need is a strong antijamming capability, lower cost, this is also offline puter (such as home PC) the main difference. Single chip.A not very plex functions using pure hardware to get the words of the 1950s developed 74 series, or 60 during the CD4000 series, the circuit must be a big PCB board! If successful on the market in the United States in the 1970s series of microcontrollers, the result will be different! Just because a program written by the MCU through you can achieve high intelligence, high efficiency and high reliability! Microcontroller for cost sensitive, so accounting for the dominance of the software or the lowest level assembly language, which is the lowest level than binary machine code language, since such lowlevel why use it? A lot of highlevel language has reached a level of visual programming, why not? The equipment, navigation systems, home appliances and so on. A variety of products using the SCM, you can play the effect of product upgrades, often preceded by an adjective in front of the product name smart, such as smart washing machines. Some factories or other amateur electronics developers to engage in out of certain products, not the circuit is too plicated, too simple and can easily be imitation. The reason may be stuck in the product does not use a microcontroller or other programmable logic devices.單片微型計(jì)算機(jī)簡稱單片機(jī)，是典型的嵌入式微控制器(Microcontroller Unit)，常用英文字母的縮寫MCU表示單片機(jī)，它最早是被用在工業(yè)控制領(lǐng)域。基于這一系統(tǒng)的單片機(jī)系統(tǒng)直到現(xiàn)在還在廣泛使用。 　　單片機(jī)比專用處理器更適合應(yīng)用于嵌入式系統(tǒng)，因此它得到了最多的應(yīng)用。概括的講：一塊芯片就成了一臺計(jì)算機(jī)。一個(gè)不是很復(fù)雜的功能要是用美國50年代開發(fā)的74系列，或者60年代的CD4000系列這些純硬件來搞定的話，電路一定是一塊大PCB板！但是如果要是用美國70年代成功投放市場的系列單片機(jī)，結(jié)果就會(huì)有天壤之別！只因?yàn)閱纹瑱C(jī)的通過你編寫的程序可以實(shí)現(xiàn)高智能，高效率，以及高可靠性！可以說，二十世紀(jì)跨越了三個(gè)“電”的時(shí)代，即電氣時(shí)代、電子時(shí)代和現(xiàn)已進(jìn)入的電腦時(shí)代?，F(xiàn)在，這種單片機(jī)的使用領(lǐng)域已十分廣泛，如智能儀表、實(shí)時(shí)工控、通訊設(shè)備、導(dǎo)航系統(tǒng)、家用電器等。數(shù)碼管個(gè)位數(shù)存放內(nèi)存位置 B_BIT EQU 21H 。//此段為燈閃5次,無實(shí)際意義 。蜂鳴器斷續(xù)鳴叫MAIN1_1_A: CLR 。//再次查看 CLR JNB ,$。//////////上面這一段是讀取溫度后進(jìn)行轉(zhuǎn)換的意思! 。///////////////////////////////// 。將溫度高位和低位從DS18B20中讀出 MOV R1,29H。十位在A MOV B_BIT,B。顯示1MS SETB MOV A,A_