【正文】 gramand data memory. In this mode, P0 has internalpullups.Port 0 also receives the code bytes during Flash programming and outputs the code bytes during program verification. External pullups are required during program verification.Port 1Port 1 is an 8bit bidirectional I/O port with internal Port 1 output buffers can sink/source four TTL 1s are written to Port 1 pins, they are pulled high bythe internal pullups and can be used as inputs. As inputs,Port 1 pins that are externally being pulled low will sourcecurrent (IIL) because of the internal pullups. In addition, and can be configured to be thetimer/counter 2 external count input () and thetimer/counter 2 trigger input (), respectively, asshown in the following 1 also receives the loworder address bytes duringFlash programming and verification.Port 2Port 2 is an 8bit bidirectional I/O port with internal Port 2 output buffers can sink/source four TTL 1s are written to Port 2 pins, they are pulled high bythe internal pullups and can be used as inputs. As inputs,Port 2 pins that are externally being pulled low will sourcecurrent (IIL) because of the internal pullups.Port 2 emits the highorder address byte during fetches from external program memory and during accesses to external data memory that use 16bit addresses (MOVX DPTR). In this application, Port 2 uses strong internal pullups when emitting 1s. During accesses to external data memory that use 8bit addresses (MOVX RI), Port 2 emits the contents of the P2 Special Function Register.Port 2 also receives the highorder address bits and some control signals during Flash programming and verification.Port 3Port 3 is an 8bit bidirectional I/O port with internal Port 3 output buffers can sink/source four TTL 1s are written to Port 3 pins, they are pulled high by the internal pullups and can be used as inputs. As inputs,Port 3 pins that are externally being pulled low will source current (IIL) because of the 3 also serves the functions of various special features of the AT89S52, as shown in the following table. Port 3 also receives some control signals for Flash programming and verification.RSTReset input. A high on this pin for two machine cycles while the oscillator is running resets the device. This pin drives High for 96 oscillator periods after the Watchdog times DISRTO bit in SFR AUXR (address 8EH) can be used to disable this feature. In the default state of bit DISRTO,the RESET HIGH out feature is enabled.ALE/PROGAddress Latch Enable (ALE) is an output pulse for latching the low byte of the address during accesses to external memory. This pin is also the program pulse input (PROG)during Flash programming. In normal operation, ALE is emitted at a constant rate of1/6the oscillator frequency and may be used for external timing or clocking purposes. Note, however, that one ALEpulse is skipped during each access to external data memory. If desired, ALE operation can be disabled by setting bit 0 of SFR location 8EH. With the bit set, ALE is active only during a MOVX or MOVC instruction. Otherwise, the pin is weakly pulled high. Setting the ALEdisable bit has no effec。借此，我覺得日后還需要在以下幾個(gè)方面進(jìn)行一些改進(jìn)：（1）提高時(shí)間的計(jì)時(shí)精度；（2）拓展電子鐘的功能，如增加溫度檢測(cè)、溫度顯示功能、星期、日、年、遙控控制等功能。鬧鈴聲為蜂鳴器長鳴3秒鐘。使儀器對(duì)測(cè)量結(jié)果的影響減少到最低。這些功能具體為：（1）原理布圖 （2）SPICE電路仿真（3）PCB自動(dòng)或人工布線具有革命性的特點(diǎn)的則有： （1）互動(dòng)的電路仿真。我們通過2051單片機(jī)的基本的C語言進(jìn)行其邏輯編程，使其達(dá)到我們需要的功能。這兩個(gè)引腳如果把微調(diào)石英晶體振蕩器和電容跨接，就組成了一個(gè)自激振蕩器[5]。只需接一個(gè)電容把RST復(fù)位引腳連接到VCC，再接一個(gè)電阻連接到地就搞定了。 多功能數(shù)字電子鐘技術(shù)路線、流程圖多功能數(shù)字電子鐘鐘 鬧鈴按鍵模塊定時(shí)時(shí)間顯示校時(shí) 結(jié)構(gòu)功能圖NYYN系統(tǒng)初始化開外部中斷有無按鍵按下?讀定時(shí)器獲取時(shí)間信息LED數(shù)碼管顯示當(dāng)前時(shí)間T=T?繼續(xù)按鍵處理子程序開始鬧鈴處理子程序 數(shù)字時(shí)鐘流程圖時(shí)鐘的功能：上電后會(huì)顯示出10：10：00 ，寄意十全十美。MCS51是由包含PC在內(nèi)的一共有22個(gè)特殊功能的寄存器，每個(gè)除了有特定的名稱外，還擁有各自確定的地址，離散的分布于片內(nèi)RAM中，具體是在80H～FFH，共128個(gè)存儲(chǔ)單元中。 F0當(dāng)對(duì)端口寫1時(shí)，經(jīng)過內(nèi)部的上拉電阻實(shí)現(xiàn)了端口拉=至高電位，這時(shí)具有作輸入口的功用。由于單片機(jī)具備質(zhì)量輕，體積小，價(jià)格便宜的優(yōu)點(diǎn)；強(qiáng)大的控制功能，豐富的指令；抗干擾能力強(qiáng)；IO引腳相對(duì)較少；片內(nèi)存儲(chǔ)器容量比較小等諸多特點(diǎn)，因此其在日常家電，游戲機(jī)，幼童玩具，儀表儀器，計(jì)算機(jī)的外圍設(shè)備，機(jī)電一體化的產(chǎn)品，分布式的監(jiān)控，工業(yè)控制等諸多領(lǐng)域有著廣泛的應(yīng)用。(2)大力發(fā)展專用單片機(jī)專用型與通用型的區(qū)別是經(jīng)過某一型號(hào)單片機(jī)具體能夠適用的范圍區(qū)分的。單片機(jī)MCS51系列的一經(jīng)推出，標(biāo)志了Single Chip Microputer體系結(jié)構(gòu)已經(jīng)趨于完善?！　≈悄芑瘍x器儀表的突出優(yōu)點(diǎn)可以體現(xiàn)在：①智能化儀器儀表能夠做到靈活多變的輸出信息；②智能化儀器儀表有自行檢測(cè)故障的功能；③智能化儀器儀表能夠?qū)?fù)雜的被測(cè)信號(hào)進(jìn)行相應(yīng)的計(jì)算和正確處理的功能，增強(qiáng)儀器儀表的實(shí)用性；④智能化儀器儀表通過切換自動(dòng)量程，可以提高分辨率與精度；⑤智能化儀器儀表有自行修復(fù)誤差功能；⑥智能化儀器儀表具有實(shí)現(xiàn)多參數(shù)/多回路的精準(zhǔn)監(jiān)測(cè)功能；⑦智能化儀器儀表具有對(duì)特定信號(hào)實(shí)行定點(diǎn)、定時(shí)測(cè)量強(qiáng)大功能。單片機(jī)這個(gè)”心臟”，做電子鐘的核心控制器用時(shí)，電子鐘計(jì)時(shí)功能就可以通過時(shí)鐘信號(hào)實(shí)現(xiàn)，單片機(jī)就能輸出時(shí)間數(shù)據(jù)，顯示器就能顯示出來相應(yīng)的結(jié)果，定時(shí)、校時(shí)功能由配置的鍵盤控制。這正是中國制表業(yè)發(fā)展和未來的方向。經(jīng)實(shí)驗(yàn)證明，振蕩部分如果使用石英晶體作為時(shí)間基準(zhǔn)信號(hào)源，那么鐘表計(jì)時(shí)變得更精確、調(diào)整起來更加方便。據(jù)史料的記載，紀(jì)元前漢武帝太初年間，落下閎這位才子創(chuàng)造了渾天儀，這是表示天體運(yùn)動(dòng)最早的儀器。本次畢業(yè)設(shè)計(jì)的電子時(shí)鐘系統(tǒng)由時(shí)鐘電路，LED顯示電路，定時(shí)報(bào)警電路，按鍵調(diào)整電路組成。鑒于石英鐘如此精確的計(jì)時(shí)，英國格林尼治天文臺(tái)于1942年也開始選用了石英鐘作為御用計(jì)時(shí)工具。當(dāng)今中國的電子業(yè)發(fā)展十分快速，達(dá)到了日新月異的程度，電子業(yè)的快速發(fā)展同時(shí)也促進(jìn)了鐘表業(yè)的發(fā)展。 研究狀況數(shù)字電子時(shí)鐘從誕生起，憑借自己的強(qiáng)大魅力就成為人類的好伙伴，給人們的生活、工作、學(xué)習(xí)、娛樂提供各種各樣的便利。為了避免混淆不同的控制器，只需一個(gè)控制器就能夠做到對(duì)各種電器進(jìn)行操作；也可以增添溫度傳感器，實(shí)時(shí)掌握溫度，擴(kuò)展到利用溫度的不同實(shí)現(xiàn)對(duì)某些特定的電氣產(chǎn)品進(jìn)行數(shù)字自動(dòng)的操控；也可增加濕度傳感器，通過對(duì)實(shí)時(shí)濕度測(cè)量，對(duì)濕度進(jìn)行控制，實(shí)現(xiàn)數(shù)字化的方便人性化的健康生活。Intel8031指令系統(tǒng)是目前比較廣泛運(yùn)用的系統(tǒng)，所有兼容這個(gè)指令系統(tǒng)的單片機(jī)統(tǒng)稱為51單片機(jī)，該系列單片機(jī)的鼻祖為Intel的8031單片機(jī)，后來Flansh rom技術(shù)不斷的發(fā)展，8031單片機(jī)成為了當(dāng)前應(yīng)用最廣泛的8位單片機(jī)之一[12]。為了達(dá)到滿足不同的要求，涌現(xiàn)出了高速、運(yùn)算功能強(qiáng)大、尋址快范圍廣和可以多機(jī)通信的132位三種的升級(jí)版通用型單片機(jī)，還有外圍系統(tǒng)集成、袖珍廉價(jià)型的專用型單片機(jī)，形形色色各具特色的現(xiàn)代單片機(jī)陸續(xù)出現(xiàn)在大家的面前。8038051和8751等通用產(chǎn)品是MCS51系列單片機(jī)的主要組成，其主要的功能具體有：8位CPU、數(shù)據(jù)存儲(chǔ)器(RAM) 、程序存儲(chǔ)器(ROM)111條指令（大部分為單字節(jié)指令）、32條I/O口線可編程定時(shí)/計(jì)數(shù)器、專用寄存器全雙工串行通信口邏輯操作的位尋址功能、外部程序的存儲(chǔ)器尋址、外部數(shù)據(jù)的存儲(chǔ)器尋址單一+5V電源供電由于51MCU擁有性能比較優(yōu)越的專用寄存器、統(tǒng)一管理和典型的網(wǎng)絡(luò)結(jié)構(gòu)，對(duì)于擁有控制方式多樣的指令系統(tǒng)以及眾多邏輯位控制功能，被稱作一代“名機(jī)”，巨大的效益等等都為以后的其它單片機(jī)的發(fā)展奠定了不可磨滅的堅(jiān)實(shí)基礎(chǔ)。 AT98C2051外部引腳圖 D4 D3一個(gè)能夠?qū)ぶ?4KB 的16位寄存器 。靜態(tài)驅(qū)動(dòng)有顯示的亮度高、編程方便簡單的優(yōu)點(diǎn)，缺點(diǎn)則是占用I/O端口較多，實(shí)際應(yīng)用時(shí)還需要添加譯碼驅(qū)動(dòng)器實(shí)現(xiàn)驅(qū)動(dòng)，麻煩使得硬件電路更加復(fù)雜。 本章小結(jié)本章主要是關(guān)于AT89C2051單片機(jī)的模塊介紹，包括引腳電器性能、內(nèi)部單元、片內(nèi)工作寄存器組、存儲(chǔ)器等；LED顯示模塊是關(guān)于LED數(shù)碼管的原理和LED數(shù)碼管驅(qū)動(dòng)方式 ；多功能數(shù)字電子鐘技術(shù)路線等。電路圖如圖42所示：，則表示有鍵按下，進(jìn)行相應(yīng)操作 ；當(dāng)變?yōu)榈碗娖綍r(shí)，則停止，則表示有鍵按下，進(jìn)行相應(yīng)操作；當(dāng)變?yōu)榈碗娖綍r(shí)，則停止，則表示有鍵按下，進(jìn)行相應(yīng)操作；當(dāng)變?yōu)榈碗娖綍r(shí)，則停止 時(shí)鐘電路如果單片機(jī)跟人一樣有心臟的話，那就是時(shí)鐘，因?yàn)閱纹瑱C(jī)中的各個(gè)功能部件的運(yùn)行都需要以時(shí)鐘頻率作為基準(zhǔn)，隨著時(shí)鐘頻率井然有序的工作。通過變壓器變壓可以使220V電壓變?yōu)槲覀冃枰? V，在利用橋式整流[3]，穩(wěn)壓器的穩(wěn)壓作用，電容的濾波作用，達(dá)到輸出穩(wěn)定的5V電壓。它是目前使用最多最好的仿真單片機(jī)和仿真外圍器件的工具。（1）Protues能夠提供大量仿真元器件：數(shù)千種交流和直流元器件、模擬和仿真數(shù)字，元件庫有30多個(gè)。 數(shù)字電子鐘時(shí)鐘功能展示圖，上電后會(huì)顯示出10：10：00 ，寄意十全十美。本次設(shè)計(jì)對(duì)