【正文】 址是相同的，但在物理上它們是分開的。欲使 CPU 僅 訪問外部程序存儲器 (地址為0000HFFFFH ) 。 （ 6） P3 口 :P3 口是一組帶有內(nèi)部上拉電阻的 8 位雙向 I/O 口。對端口寫“ 1”，通過內(nèi)部的上拉電阻把端口拉到高電平，此時可作輸入口。 三、實現(xiàn)方案簡介 DS18B20 采用外接電源方式工作，一線測溫的一線與 AT89C52 的 連接并加上上拉電阻使其工作，測出的數(shù)據(jù)存直接顯示在 LED 顯示器上。因此本溫度計成本降低，使用起來更加的方便。 單片機課程設(shè)計論文 指導教師：基于 DS18B20 數(shù)字溫度計的設(shè)計 1 摘 要 本論文主要講述了數(shù)字溫度計的設(shè)計過程，主要包括硬件設(shè)計和程序設(shè)計。 關(guān)鍵詞：單片機、顯示電路、溫度傳感器 DS18B20 基于 DS18B20 數(shù)字溫度計的設(shè)計 2 目錄 1. 設(shè)計任務及方案分析 2. 芯片功能簡介 3. 硬件系統(tǒng)電路設(shè)計 （一定要有硬件連接圖） 4. 軟件編程調(diào)試及性能分析 （應該包含程序框圖和程序） 總結(jié) 參考文獻 謝辭 基于 DS18B20 數(shù)字溫度計的設(shè)計 3 1. 設(shè)計任務 及方案分析 一、任務要求 設(shè)計內(nèi)容 ： 用單片機、溫度傳感器等器件實現(xiàn)溫度采集， 要求采集的溫度精確到 設(shè)計要求： ?？傮w方案框圖如下圖所示。作輸入口使用時，因為內(nèi)部存在上拉電阻，某個引腳被外部信號拉低時會輸出一個電流 (ILL)。 P3 口輸出緩沖級可驅(qū)動 (吸收或輸出電流 )4 個 TTL 邏輯門電路。 EA 端必須保持低電平 (接地 )。 基于 DS18B20 數(shù)字溫度計的設(shè)計 7 當一條指令訪問 7FH 以上的內(nèi)部地址單元時，指令中使用的尋址方式是不同的，也即尋址方式?jīng)Q定是訪問高 128 字節(jié)。采用外部時鐘的電路如圖 41（ b）圖所示。 （ 5） 可編程的分辨率為 9～ 12 位，對應的可分辨溫度分別為 ℃ 、 ℃ 、℃ 和 ℃ ，可實現(xiàn)高精度測溫 。 3 VDD 可選擇的 VDD 引腳。 例如＋ ℃的數(shù)字輸出為 0191H，－ ℃的數(shù)字輸出為 FF6FH。高速暫存器 RAM 結(jié)構(gòu)圖如下表 2 所示。主機在讀時間片下降沿之后 15us 內(nèi)基于 DS18B20 數(shù)字溫度計的設(shè)計 12 完成讀位。只有和 64 位 ROM 序列 完全匹配的DS18B20 才能響應隨后的存儲器操作。 （ 5） Alarm Search [0ECH] 這條命令的流程和 Search ROM 相同。如果不想讀完所有字節(jié)，控制器可以在任何時刻發(fā)出復位命令來中止讀取。 （ 10） Read E2 [0B8H] 這條命令把 觸發(fā)器里的值拷貝回暫存器。 sbit p20=P2^0。 void delay(unsigned int i) { while(i)。 x=DQ。 j++。 } //寫一個字節(jié)程序 write(unsigned char dat) { unsigned char i=0。 dat=1。 DQ=1。 p21=1。 p23=1。 基于 DS18B20 數(shù)字溫度計的設(shè)計 21 a=read()。 shi=t/10。 p21=1。 p23=1。 p21=0。 p23=0。 for(count=0。 P0=tab[shi]。 基于 DS18B20 數(shù)字溫度計的設(shè)計 25 p23=1。 } else p20=0。 p22=0。t appealed against the disciplinary action your employer has taken against you. However, if you win your case, the tribunal may reduce any pensation awarded to you as a result of your failure to appeal. Remember that in most cases you must make an application to an employment tribunal within three months of the date when the event you are plaining about happened. If your application is received after this time limit, the tribunal will not usually accept it. If you are worried about how the time limits apply to you, take advice from one of the anisations listed under Further help. Employment tribunals are less formal than some other courts, but it is still a legal process and you will need to give evidence under an oath or affirmation. Most people find making a claim to an employment tribunal challenging. If you are thinking about making a claim to an employment tribunal, you should get help straight away from one of the anisations listed under Further help. If you are being represented by a solicitor at the tribunal, they may ask you to sign an agreement where you pay their fee out of your pensation if you win the case. This is known as a damagesbased agreement. In England and Wales, your solicitor can39。s governing body, has also ordered an immediate investigation into the referee39。 Junior high school, thought to have a crush on just means that the real growth, but over the past three years later, his writing of alumni in peace, suddenly found that isn39。想要的，不想要的，界限明確，好像沒有什么可以撼動自己。t start planning... Those years, those days of do, finally, like youth, will end in our life. 此刻，天空 是陰暗的，空氣里有著剛下過雨之后的清新因子。 Baumgartner the disappointing news: Mission aborted. r plays an important role in this mission. Starting at the ground, conditions have to be very calm winds less than 2 mph, with no precipitation or humidity and limited cloud cover. The balloon, with capsule attached, will move through the lower level of the atmosphere (the troposphere) where our daytoday weather lives. It will climb higher than the tip of Mount Everest ( miles/ kilometers), drifting even higher than the cruising altitude of mercial airliners ( miles/ kilometers) and into the stratosphere. As he crosses the boundary layer (called the tropopause),e can expect a lot of turbulence. The supersonic descent could happen as early as Sunda. The weatheThe balloon will slowly drift to the edge of space at 120,000 feet ( Then, I would assume, he will slowly step out onto something resembling an Olympic div