【正文】 ctricity, electronic era and now has entered the puter era. However, this kind of puter, usually refers to the personal puter, the abbreviation PCS. It consists of host, keyboard, display etc. And those puter, most people do not so familiar with. This puter is intelligence gives all kinds of mechanical SCM (also called micro controller). As the name suggests, the puter is minimal systems only took a piece of integrated circuits, simple operation and control can be carried out. Because of its small size, usually hidden in the accused of mechanical stomach. It in the whole device, plays the role of like the human mind, it went wrong, the whole device broke down. Now, this SCM use field has been widely, such as intelligent instruments, realtime control, munication equipment, navigation system, household electric appliances, etc. Various products once using singlechip microputer, can have the effect that product upgrading, often in product specialty bariatric adjectives intelligent, such as intelligent washing machines etc. Now some factories technicians or other leisure electronic developers out some of the products, not the circuits are too plex, is functional too simple and the easy be imitators. Investigate its reason, may be stuck in product without using SCM or other programmable logic devices. . Microcontroller history 1971 Intel pany developed the world39。s first four microprocessor, The Intel pany hoff successfully developed the world39。s first piece of four 4004 Intel microprocessor chips, marks the first generation of microprocessor market, microprocessor and puter era begins. For invention microprocessor, hoff by the British economist magazine named the most influential since world war ii the seven scientists one. In 1971, the Intel on November launch MCS 4 microputer system (including 4001 ROM chip, 4002 RAM chips, 4003 shift register chips and 4004 microprocessor) which 4004 (figure below) contains 2,300 transistor, the dimension of 3mm x 4mm, puting performance than that ENIAC, initially sells for $200. April 1972, hoff etc, developed the first eight Intel microprocessor 8008. Because 8008 USES is P in gully MOS microprocessor, and therefore still belong to the first generation of microprocessors. 1973 Intel pany develop 8 bits of the microprocessor 8080。 In 1973, August hoff person such as developed eight microprocessor 8080 to N in gully intelbased MOS circuit replaced P channel, the second generation microprocessor at birth. Frequency of 2MHz 8080 chip speed 8008 10 times faster than, can access 64KB memory, use based on six micron technology 6,000 transistors, processing speed of the MIPS (at) Million will conference. In 1975, MITS issued on April first generalpurpose Altair 8,800, price $, with 1KB memory. This is the world39。s first microputer. 1976 the Intel pany develop MCS 48 series of 8 bits of single chip microcontroller, this also is published. Zilog pany in 1976 development Z80 microprocessor, widely used in microputer and industrial automatic control equipment. At that time, Zilog, Motorola and Intel microprocessor field in Japan. In the early 1980s, the Intel pany in MCS 48 series microcontroller, on the basis of launched MCS 51 series 8 bits of highgrade microcontroller. MCS 51 series microcontroller whether pieces (RAM capacity, I/O mouth function, system extension aspects had the very big enhancement. Singlechip the bus: we know that a circuit is always from the ponents through wires connected, and in analog circuits, the connection does not bee a problem, because the devices are generally serial interrelationship between the various devices connection is not much, but not the same as puter circuits, which is based on the microprocessor as the core, the device must be connected with the microprocessor, the device must be between the mutual coordination and so on need to connect on a lot of If still the same as analog circuits, in the microprocessor and a separate connection between the devices, the quantity line will be many alarmingly so in the microprocessor introduced the concept of bus, all devices share the connection All devices of all eight data lines from eight public online, which is equivalent to all devices in parallel, but only this is not enough, if there is two devices send data simultaneously, a 0, a 1, then , the receiving party received what is it? This situation is not allowed, so to pass the line of control to control the device time job, any time there can be only one device to send data (which may have multiple devices simultaneously receiving). Device39。s data lines will be referred to as data bus, all the line of control devices known as control bus. Singlechip at internal or external memory and other devices have memory cells, these memory cells to be assigned addresses to use, the allocation of addresses is of course to give the form of electrical signals, and because memory cells are more so for address the allocation of more lines, these lines were known as the address bus. Second, data, address, mand: The reason why these three together, because these three are the essence is the same figure, or are a string of39。0 39。and39。139。, posed of sequence . In other words, addresses, instructions are also data. Command: from singlechip chip designer provides a figure, it is consistent with our mnemonic monly used mands have a strict onetoone relationship, not by the developer to change the MCU. Address: Singlechip are looking for internal, external storage units, input and output port based on the value of the internal unit39。s address has been provided for the chip designers, and can not be changed, the external unit can be singlechip developers to decide, but Yes there is some address must be the unit (see procedures for the implementation process). Data: This is the object