【正文】 ed addresses, you can use, distribution, of course, to address given in the form of electrical signals, and as more memory cells, so, for the address allocation The line is also more of these lines is called the address bus.Second, data, address, mandThe reason why these three together because of the nature of these three are the same the number, or are a string of 39。s dedicated processor, while the average model prices fall to one . dollars, the most highend [1] model only 10 SCM systems are no longer only in the development and use of bare metal environment, a large number of proprietary embedded operating system is widely used in the full range of SCM. The handheld puters and cell phones as the core processing of highend microcontroller can even use a dedicated Windows and Linux operating systems.SCM is more suitable than the specific processor used in embedded systems, so it was up to the application. In fact the number of SCM is the world39。四、程序的執(zhí)行過程：單片機(jī)在通電復(fù)位后8051內(nèi)的程序計(jì)數(shù)器（PC）中的值為‘0000’，所以程序總是從‘0000’單元開始執(zhí)行，也就是說：在系統(tǒng)的ROM中一定要存在‘0000’這個單元，并且在‘0000’單元中存放的一定是一條指令。 二、數(shù)據(jù)、地址、指令：之所以將這三者放在一起，是因?yàn)檫@三者的本質(zhì)都是一樣的——數(shù)字，或者說都是一串‘0’和‘1’組成的序列。如音樂集成單片機(jī)，看似簡單的功能，微縮在純電子芯片中（有別于磁帶機(jī)的原理），就需要復(fù)雜的類似于計(jì)算機(jī)的原理。 單片機(jī)廣泛應(yīng)用于儀器儀表、家用電器、醫(yī)用設(shè)備、航空航天、專用設(shè)備的智能化管理及過程控制等領(lǐng)域，大致可分如下幾個范疇： 單片機(jī)具有體積小、功耗低、控制功能強(qiáng)、擴(kuò)展靈活、微型化和使用方便等優(yōu)點(diǎn)，廣泛應(yīng)用于儀器儀表中，結(jié)合不同類型的傳感器，可實(shí)現(xiàn)諸如電壓、功率、頻率、濕度、溫度、流量、速度、厚度、角度、長度、硬度、元素、壓力等物理量的測量。因此，當(dāng)我們回顧嵌入式系統(tǒng)發(fā)展道路時，不要忘記Intel和Philips的歷史功績。 起初模型（Single Chip Microputer）階段，主要是尋求最佳的單片形態(tài)嵌入式系統(tǒng)的最佳體系結(jié)構(gòu)。顧名思義，這種計(jì)算機(jī)的最小系統(tǒng)只用了一片集成電路，即可進(jìn)行簡單運(yùn)算和控制。一個可視化高級語言編寫的小程序里面即使只有一個按鈕，也會達(dá)到幾十K的尺寸！對于家用PC的硬盤來講沒什么，可是對于單片機(jī)來講是不能接受的。它的體積小、質(zhì)量輕、價格便宜、為學(xué)習(xí)、應(yīng)用和開發(fā)提供了便利條件。事實(shí)上單片機(jī)是世界上數(shù)量最多的計(jì)算機(jī)。隨著工業(yè)控制領(lǐng)域要求的提高，開始出現(xiàn)了16位單片機(jī)，但因?yàn)樾詢r比不理想并未得到很廣泛的應(yīng)用。中文譯文單片機(jī)單片機(jī)也被稱為微控制器（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?；谶@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！ 由于單片機(jī)對成本是敏感的，所以目前占統(tǒng)治地位的軟件還是最低級匯編語言，它是除了二進(jìn)制機(jī)器碼以上最低級的語言了，既然這么低級為什么還要用呢？很多高級的語言已經(jīng)達(dá)到了可視化編程的水平為什么不用呢？原因很簡單，就是單片機(jī)沒有家用計(jì)算機(jī)那樣的CPU，也沒有像硬盤那樣的海量存儲設(shè)備。這種計(jì)算機(jī)就是把智能賦予各種機(jī)械的單片機(jī)（亦稱微控制器）。 單片機(jī)歷史單片機(jī)誕生于20世紀(jì)70年代末，經(jīng)歷了SCM、MCU、SoC三大階段。 Philips公司以其在嵌入式應(yīng)用方面的巨大優(yōu)勢，將MCS51從單片微型計(jì)算機(jī)迅速發(fā)展到微控制器。因此，單片機(jī)的學(xué)習(xí)、開發(fā)與應(yīng)用將造就一批計(jì)算機(jī)應(yīng)用與智能化控制的科學(xué)家、工程師。 某些專用單片機(jī)設(shè)計(jì)用于實(shí)現(xiàn)特定功能，從而在各種電路中進(jìn)行模塊化應(yīng)用，而不要求使用人員了解其內(nèi)部結(jié)構(gòu)。在單片機(jī)內(nèi)部或者外部存儲器及其它器件中有存儲單元，這些存儲單元要被分配地址，才能使用，分配地址當(dāng)然也是以電信號的形式給出的，由于存儲單元比較多，所以，用于地址分配的線也較多，這些線被稱為地址總線。你完全可以在指令中按排一條SETB ，并且當(dāng)單片機(jī)執(zhí)行到這條指令時，但使用者不會這么去做，因?yàn)檫@通常會導(dǎo)致系統(tǒng)的崩潰。sZ80 is the first designed in accordance with this idea processor, then on the development of microcontroller and dedicated processors have parted ways.Are 8bit microcontroller early or4 bits. One of the most successful is the INTEL 8031, for a simple, reliable and good performance was a lot of praise. Then developed in 8031 out of MCS51 MCU Systems. SCM systems based on this system until now is still widely used. With the increased requirements of industrial control field, began a 16bit microcontroller, because the cost is not satisfactory but have not been very widely used. After 90 years with the great development of consumer electronics, microcontroller technology has been a huge increase. With INTEL i960 series, especially the later series of widely used ARM, 32bit microcontroller quickly replace highend 16bit MCU status and enter the mainstream market. The traditional 8bit microcontroller performance have been the rapid increase capacity increase pared to 80 the number of times. Currently, highend 32bit microcontroller clocked over 300MHz, the performance catching the mid9039。 Therefore, the development of dedicated single chip SOC trend of the natural form. As the microelectronics, IC design, EDA tools development, application system based on MCU SOC design have greater development. Therefore, the understanding of the microcontroller chip microputer can be, extended to the singlechip microcontroller applications.MCU applicationsSCM now permeate all areas of our lives, which is almost difficult to find traces of the field without SCM. Missile navigation equipment, aircraft, all types of instrument control, puter network munications and data transmission, industrial automation, realtime process control and data processing, extensive use of various smart IC card, civilian luxury car security system, video recorder, camera, fully automatic washing machine control, and programcontrolled toys, electronic pet, etc., which are inseparable from the microcontroller. Not to mention the area of robot control, intelligent instruments, medical equipment was. Therefore, the MCU learning, development and application of the large number of puter applications and intelligent control of the scientists, engineers. SCM is widely used in instruments and meters, household appliances, medic