【正文】 indispensable tool, especially in this era of efficient, the clock is in the human production and living, learning and other fields is widely. However, with the passage of time, people not only to the requirements of the clock is getting higher and higher precision, and functional requirements for the clock more and more, the clock has not only a tool used to display time, in many practical applications It also needs to be able to achieve more other functions. Features such as alarm clock, calendar display, temperature measurement function, humidity measurements, voltage measurements, frequency measurements, have been undervoltage alarm function. Digital clocks to the people39。諸如鬧鐘功能、日歷顯示功能、溫度測(cè)量功能、濕度測(cè)量功能、電壓測(cè)量功能、頻率測(cè)量功能、過欠壓報(bào)警功能等。高精度、多功能、小體積、低功耗，是現(xiàn)代時(shí)鐘發(fā)展的趨勢(shì)。同時(shí)，該時(shí)鐘系統(tǒng)還具有功耗小、成本低的特點(diǎn)，具有很強(qiáng)的實(shí)用性。在實(shí)際的時(shí)鐘模型中，我們要考慮時(shí)鐘樹傳播中的偏斜、跳變和絕對(duì)垂直的偏差以及其它一些不確定因素。門控時(shí)鐘在許多應(yīng)用中，整個(gè)設(shè)計(jì)項(xiàng)目都采用外部的全局時(shí)鐘是不可能或不實(shí)際的。邏輯門的一個(gè)輸入作為實(shí)際的時(shí)鐘，而該邏輯門的所有其它輸入必須當(dāng)成地址或控制線，它們遵守相對(duì)于時(shí)鐘的建立和保持時(shí)間的約束。多時(shí)鐘系統(tǒng)許多系統(tǒng)要求在同一個(gè)PLD內(nèi)采用多時(shí)鐘。9。由于兩個(gè)時(shí)鐘信號(hào)之間要求一定的建立和保持時(shí)間，所以，上述應(yīng)用引進(jìn)了附加的定時(shí)約束條件。即使樣機(jī)或仿真結(jié)果沒有顯示出靜態(tài)險(xiǎn)象，但實(shí)際上仍然可能存在著危險(xiǎn)。然而，當(dāng)你用陣列時(shí)鐘時(shí)，應(yīng)仔細(xì)地分析時(shí)鐘函數(shù)，以避免毛刺。數(shù)據(jù)同樣應(yīng)該在時(shí)鐘工作沿過去后保持一段時(shí)間，這段時(shí)間稱為保持時(shí)間（hold time）。時(shí)鐘設(shè)計(jì)無淪是用離散邏輯、可編程邏輯，還是用全定制硅器件實(shí)現(xiàn)的任何數(shù)字設(shè)計(jì)，為了成功地操作，可靠的時(shí)鐘是非常關(guān)鍵的。本文正是基于這種設(shè)計(jì)方向，以單片機(jī)為控制核心，設(shè)計(jì)制作一個(gè)符合指標(biāo)要求的多功能數(shù)字時(shí)鐘。諸如定時(shí)自動(dòng)報(bào)警、按時(shí)自動(dòng)打鈴、時(shí)間程序自動(dòng)控制、定時(shí)廣播、自動(dòng)起閉路燈、定時(shí)開關(guān)烘箱、通斷動(dòng)力設(shè)備、甚至各種定時(shí)電氣的自動(dòng)啟用等，所有這些，都是以鐘表數(shù)字化為基礎(chǔ)的。 外文資料翻譯L ED using digital tube digital display its highbrightness, indicating the advantages of intuitive intelligence is widely used in areas such as equipment and household appliances. AT89C52This article describes a singlechip microputer as the core, to a total of anode highbrightness LED L ED as a display posed of seven figures show that the practical design of multifunction electronic clocks, the clock shows a week, hour, minute, second, it can be switched to year, month, day showed that the whole point of music at the same time and from time to time the alarm time and other functions can also be used for electronic stopwatch.Clock circuit is the heart of the puter, which controls the rhythm of the work of the puter is through the pletion of plex sequential circuits function in different directions.Clock, since it was invented that day on, people39。鐘表的數(shù)字化給人們的生產(chǎn)生活帶來了極大的方便，而且大大地?cái)U(kuò)展了鐘表原先的報(bào)時(shí)功能。在這種趨勢(shì)下，時(shí)鐘的數(shù)字化、多功能化已經(jīng)成為現(xiàn)代時(shí)鐘生產(chǎn)研究的主導(dǎo)設(shè)計(jì)方向。由于系統(tǒng)所用元器件較少，單片機(jī)所被占用的I/O口不多，因此系統(tǒng)具有一定的可擴(kuò)展性。對(duì)于寄存器而言，當(dāng)時(shí)鐘工作沿到來時(shí)它的數(shù)據(jù)端應(yīng)該已經(jīng)穩(wěn)定，這樣才能保證時(shí)鐘工作沿采樣到數(shù)據(jù)的正確性，這段數(shù)據(jù)的預(yù)備時(shí)間我們稱之為建立時(shí)間（setup time）。PLD具有乘積項(xiàng)邏輯陣列時(shí)鐘（即時(shí)鐘是由邏輯產(chǎn)生的），允許任意函數(shù)單獨(dú)地鐘控各個(gè)觸發(fā)器。多級(jí)邏輯時(shí)鐘當(dāng)產(chǎn)生門控時(shí)鐘的組合邏輯超過一級(jí)(即超過單個(gè)的“與”門或“或”門)時(shí)，證設(shè)計(jì)項(xiàng)目的可靠性變得很困難。最常見的例子是兩個(gè)異步微處理器器之間的接口，或微處理器和異步通信通道