【正文】 , military products, as well as household appliances and other fields, often singlechip microputer as a core ponent to use, in accordance with the specific hardware architecture, as well as applicationspecific features of the software object to be perfect. The graduation project through its study and application to achieve the study, design, development hardware and software capabilities. With a variety of puteraxis of the birth of information processing devices, in order to adapt to this new situation, information appliances, network terminals, radio munications, such as the use of LCD market will expand rapidly, and now not only the development direction of LCD to the big screen, but also in small and mediumsized screen, such as car navigation systems, video cameras, digital cameras, portable TV, PDA (Personal Digital Assistant), entertainment / video game consoles, cameras, etc. have further development. Liquid Crystal Display (LCD) with low power consumption, small size, light weight, ultrathin displays and many other advantages unmatched in recent years been widely used in singlechip smart control devices, instrumentation and lowpower electronic products. LCD can be divided into Segment LCD, charactertype LCD and dot matrix LCD. Among them, the piece character LCD and LCDstyle characters and figures can only be used for simple display, can not satisfy the graphics curve and show that the requirements of Chinese characters。該電子鐘上電或按鍵復(fù)位后能自動(dòng)顯示系統(tǒng)提示符“P.”， 進(jìn)入時(shí)鐘準(zhǔn)備狀態(tài)；第一次按電子鐘啟動(dòng)/調(diào)整鍵，電子鐘從0時(shí)0分0秒開始運(yùn)行，進(jìn)入時(shí)鐘運(yùn)行狀態(tài)；再次按電子鐘啟動(dòng)/調(diào)整鍵，則電子鐘進(jìn)入時(shí)鐘調(diào)整狀態(tài)，此時(shí)可利用各調(diào)整鍵調(diào)整時(shí)間，調(diào)整結(jié)束后可按啟動(dòng)/調(diào)整鍵再次進(jìn)入時(shí)鐘運(yùn)行狀態(tài)。用片內(nèi)RAM的7BH單元對(duì)50ms計(jì)數(shù)，計(jì)20次產(chǎn)生秒計(jì)數(shù)器78H單元加1，秒計(jì)數(shù)器加到60則分計(jì)數(shù)器79H單元加1，分計(jì)數(shù)器加到60則時(shí)計(jì)數(shù)器7AH單元加1，時(shí)計(jì)數(shù)器加到24則時(shí)計(jì)數(shù)器清0。顯示格式為小時(shí)十位、小時(shí)個(gè)位分十位、分個(gè)位秒十位、秒個(gè)位。2 課題硬件系統(tǒng)設(shè)計(jì) 各模塊電路簡(jiǎn)要介紹 單片機(jī)最小系統(tǒng)單片機(jī)最小系統(tǒng)包括電源電路、時(shí)鐘電路、復(fù)位電路。電源電路給單片機(jī)供電，時(shí)鐘電路給單片機(jī)提供計(jì)數(shù)時(shí)間，復(fù)位電路可以實(shí)現(xiàn)單片機(jī)的復(fù)位。 流水燈電路流水燈電路直接掛接在單片機(jī)的P3口上，采用共陽(yáng)接法。 下載口電路，2腳懸空，3腳接單片機(jī)的復(fù)位口，,，6腳接地，10腳接地。它由加法計(jì)數(shù)器、方式寄存器TMOD、控制寄存器TCON等組成。 （2）每個(gè)定時(shí)計(jì)數(shù)器既可以對(duì)系統(tǒng)時(shí)鐘計(jì)數(shù)實(shí)現(xiàn)定時(shí)，也可以外部信號(hào)計(jì)數(shù)實(shí)現(xiàn)計(jì)數(shù)功能通過編程設(shè)定來實(shí)現(xiàn)。通過編程可設(shè)定工作于某種方式。 （4）每一個(gè)定時(shí)計(jì)數(shù)器定時(shí)計(jì)數(shù)時(shí)間到時(shí)產(chǎn)生溢出，使相應(yīng)的溢出位置位，溢出可通過查詢或中斷方式處理。（2）MCS51單片機(jī)中沒有專門的開中斷和關(guān)中斷指令，對(duì)各個(gè)中斷源的允許和屏蔽是由內(nèi)部的中斷允許寄存器IE的各位來控制的。系統(tǒng)復(fù)位時(shí)，中斷允許寄存器IE的內(nèi)容為00H，如果要開放某個(gè)中斷源，則必須使IE中的總控置位和對(duì)應(yīng)的中斷允許位置“1”。通過由內(nèi)部的中斷優(yōu)先級(jí)寄存器IP來設(shè)置，中斷優(yōu)先級(jí)寄存器IP的字節(jié)地址為B8H，可以進(jìn)行位尋址。對(duì)于同級(jí)中斷源，系統(tǒng)有默認(rèn)的優(yōu)先權(quán)順序，從高到低優(yōu)先權(quán)順序?yàn)橥獠恐袛?、定時(shí)計(jì)數(shù)器T0中斷、外部中斷定時(shí)計(jì)數(shù)器T1中斷、串行口中斷。（4）MCS51單片機(jī)響應(yīng)中斷的條件為：中斷源有請(qǐng)求且中斷允許。LED數(shù)碼管顯示器是由發(fā)光二極管按一定的結(jié)構(gòu)組合起來的顯示器件。所謂譯碼方式是指由顯示字符轉(zhuǎn)換得到對(duì)應(yīng)的字段碼的方式。LED數(shù)碼管在顯示時(shí)，通常有兩種顯示方式：靜態(tài)顯示方式和動(dòng)態(tài)顯示方式。在實(shí)際應(yīng)用時(shí)，如果數(shù)碼管個(gè)數(shù)較少，通常用硬件譯碼靜態(tài)顯示，在數(shù)碼管個(gè)數(shù)較多時(shí)，則通常用軟件譯碼動(dòng)態(tài)顯示。當(dāng)按下K0按鍵時(shí)，進(jìn)入調(diào)分狀態(tài)，時(shí)鐘停止走動(dòng)即暫停；按K1或K2按鍵可進(jìn)行加1或減1操作；繼續(xù)按K0鍵可分別進(jìn)行分和小時(shí)的調(diào)整；最后按K0鍵將退出調(diào)整狀態(tài)，時(shí)鐘開始計(jì)時(shí)運(yùn)行；按K3鍵停止一切功能，顯示器呈現(xiàn)ELEC 0901(電子0901)字符。由第一個(gè)鍵開始檢測(cè)按鍵是否被按下，延時(shí)消除抖動(dòng)，判斷按鍵是否被放開，跳出執(zhí)行對(duì)應(yīng)的按鍵程序，否則檢測(cè)下一個(gè)鍵是否按下。采用軟件譯碼動(dòng)態(tài)顯示。選擇方式1，重復(fù)定時(shí)，定時(shí)時(shí)間設(shè)為50ms，定時(shí)時(shí)間到則中斷，在中斷服務(wù)程序中用一個(gè)計(jì)數(shù)器對(duì)50ms計(jì)數(shù)，計(jì)20次則對(duì)秒單元加1，秒單元加到60則對(duì)分單元加1，同時(shí)秒單元清0；分單元加到60則對(duì)時(shí)單元加1，同時(shí)分單元清0；時(shí)單元加到24則對(duì)時(shí)單元清0，標(biāo)志一天時(shí)間計(jì)滿。程序設(shè)計(jì)的流程圖如下：22圖6 主程序流程圖圖7 定時(shí)器/計(jì)數(shù)器T0中斷服務(wù)程序流程圖圖8 鍵掃描子程序流程圖圖9 數(shù)碼管顯示器顯示顯示子程序流程圖(見附錄A)4 仿真結(jié)果、設(shè)計(jì)結(jié)論及使用說明由于系統(tǒng)軟件的問題，本設(shè)計(jì)仿真不是很理想，有些代碼的生成出現(xiàn)了混亂的現(xiàn)象，但各鍵功能與運(yùn)行良好。實(shí)物運(yùn)行總體結(jié)果比較理想，不過一開始王老師指出了在按下鍵時(shí)會(huì)出現(xiàn)顯示器全滅的現(xiàn)象，經(jīng)過程序的修改，已良好的解決這一問題。從原理圖與PCB版的設(shè)計(jì)到程序的編寫，每一步都遇到了很大的困難，特別是在程序編寫時(shí)，開始時(shí)不懂