【導讀】　　單片機要自動完成計算，它應該具有哪些最重要的部分呢？我們以打算盤為例計算一道算術題。例：36＋163×156－166÷34?，F在要進行運算，首先需要一把算盤，其次是紙和筆。這類器件就稱為“存貯器”。但是光有這三部分還不夠，原始的數據與命令要輸入，計算的結果要輸出，都需要按先后順序進行，有時還需等待。所以，這一類信息就稱為控制命令，即由控制器去控制運算器一步步地進行運算和處理，又控制存貯器的讀和寫等。第三類信息是地址信息，其作用是告訴運算器和控制器在何處去取命令取數據，將結果存放到什么地方，通過哪個口輸入和輸出信息等。這些指令是用十六進制表示二進制的機器碼?！　CS－51單片機的字長為8位，有時，要完成某些操作用一個字節(jié)尚不能充分表達。所以，在指令系統(tǒng)中有單字節(jié)指令，也有多字節(jié)指令。機器碼是由一連串的0和1組成，沒有明顯的特征，不好記憶，不易理解，易出錯。用助記符來編寫的程序稱為匯編語言程序。

　　

【正文】 cial Function Registers P0 ~ P3, they are in fact four of eight latches (one for each I / O port A), each additional latch corresponding output driver and input buffer constitutes a parallel port. MCS51 a total of four such P0 ~ P3 the parallel port provides 32 I / O lines, each line is a twoway, and has the second largest function. The rest used for chip control register, the accumulator A, marks register PSW, the data pointer DPTR function mentioned before, while others function registers part of the back of the further introduction Singlechip instruction and addressing mode To the normal operation of singlechip, to be programmed in advance, and then the procedure Add memory, and then from the CPU to implement the program. Procedure is posed by the directive, Directive is an essential ponent of the operation code and operands. Many varieties of singlechip, the design of how that operation code and operands, have their own requirements, and then there are instructions code varies, therefore, must be singlechip all the selected mand, which is the socalled instruction sufficient understanding. Although the various series of singlechip systems have different mands, but also has its monality. Instructions have a singlechip system, for other series of singlechip can play a role prehend by analogy. MCS51 singlechip applications, derived varieties, representative, therefore, here to MCS51 series as an example of the mand system mand the position and , MOV A, 20H The instructions said to 20H into the accumulator A of the number of (a special function register).4. In intelligent instruments on the application Singlechip microputer with small size, low power consumption, control function is strong, flexible, miniaturization and extended use of convenience etc, widely used in instrumentation, bined with different kinds of sensors, such as voltage, power can be realized, the frequency, the humidity, temperature and flow rate, speed, thickness, Angle, length, hardness, elements, pressure measurements of physical quantities. Adopting SCM control makes instrumentation digital, intelligent, miniaturization, and function by electronic or digital circuit than more powerful. For example precision measurement equipment (power meter, oscilloscope, various analyzer).2. The application in industrial control Using SCM can make various control systems, data acquisition system. For example factory assembly line of intelligent tube 芯片chip Richard, elevator intelligent control, various alarm system, and puter networking constitute a secondary control system, etc. 3. The application in household appliances It can be said that now of household appliances basically all adopted MCU control, from electric cooker, washing machines, refrigerators, air conditioner, TVS and other audio video equipment, electronic equipment, again to amount is multifarious, omnipresent. 4. In puter network and munication field application Modern singlechip generally have the munication interface can be easily and puter data munications, for in puter network and munication between devices applied to provide the excellent material conditions, now of munication equipment basically all realized microcontroller intelligent control, from mobile, telephone, small pabx, building automatic munication call system, train wireless munication, to daily work ubiquitous mobile phone, cluster mobile munications, radios, etc. 5. Microputer in the medical device field application The USES of microputer in the medical equipment is quite widespread, such as medical also breathing machine, various analyzer, monitors, ultrasound diagnostic equipment and sickbed call system, etc. 6. In various largescale electric appliance of modular applications Some special MCU designed to acplish a specific function, thus in the various circuits for modular application, and not require staff know its internal structure. If music integration microcontroller, deceptively simple function, miniature in pure electronic chip (different from the principle of tape) be plex resemble puter principle. Such as: music signals in digital form stored in memory (ROM), similar to read by micro controller into analog signals (similar to the music sound card). In large circuit, this modular applications have greatly reduced volume, simplified the circuit, reduced damage, the error rate, also facilitate replacement. 7. Microputer in the application fields of auto equipment The application of microputer in the automotive electronics is very extensive, for example, in the car engine controller based on CAN bus automobile engine intelligence electronic controllers, GPS navigation system, abs antilock brake systems, braking system, etc. In addition, microputer in the industry and merce, finance, scientific research, education, national defence aerospace and other fields have a wide range of purposes.16