【正文】 ing true ReadWhileWrite operation. By bining an 8bit RISC CPU with InSystem Self Programmable Flash on a monolithic chip, the Atmel ATmega8 is a powerful microcon troller that provides a highlyflexible and costeffective solution to many embedded control applications. The ATmega8 AVR is supported with a full suite of program and system development tools, including C pilers, macro assemblers, program debugger/simulators, InCir cuit Emulators, and evaluation kits. MCU application Currently microcontroller perated into every aspect of our lives, almost hard to find which field no trace of single chip. Missile navigation devices, the plane on various kinds of instrument control, puter work munication and data transmission, industrial automation process realtime control and data processing, is widely used in all kinds of intelligent IC card, civil luxury car security system, video camera, video camera, fullautomatic washing machine control, as well as programcontrolled toys, electronic pets, etc, these are inseparable from microcontroller. Mention automatic control field of robot, intelligent instruments, medical equipment and various kinds of intelligent machinery. Therefore, SCM39。 POP 39。 PUSH 39。advanced after that lastin firstout 39。000039。0000 39。 unit begin implementation of, that is to say: the system39。, so the procedure always39。 as a generalpurpose I / O port to use. At mand you can arrange a Medium of Instruction SETB , and when the singlechip implementation of this Article directions, will also bee high, but users will not do so, because This usually will lead to the collapse of the system. Four, the program implementation process: singlechip poweron reset in 8051 after the program counter (PC) in the value of39。 but (user) 39。 is not 39。s second feature is pletely automatic, no need to use mand to convert. Such as , , respectively, are WR, RD signal, when the microchip RAM or external justifications machine has an external I / O port, they were used as the second function, can not be used as generalpurpose I / O port to use, as long as one microprocessor implementation of the MOVX instruction 1, there will be a corresponding signal sent from the or , no prior use instructions indicate. In fact 39。, 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。and39。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。 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 four microprocessor, The Intel pany hoff successfully developed the world39。 The single chip puter abbreviation Microcontroller is typical of embedded Microcontroller controller (Microcontroller Unit), mon English letters is the abbreviation of MCU said Microcontroller, it was first used in industrial control field. SCM by chip inside only CPU dedicated processor. The earliest design concept is through the huge amounts of peripheral and CPU integration in a chip, make the puter system smaller, more easy to integrate into the plex and to volume demanding control equipment of. Intelbased Z80 is the earliest designed according to this kind of thought the processor, henceforth, SCM and dedicated processor development parted. Early microcontroller is 8 bits or 4 digit. One of the most successful intelbased 8031 is simple, reliable performance, because good got a lot of praise. Then in the microputer 8031 developed MCS51 series microcontroller systems. Based on this system of SCM system have until now in widespread use. With the improvement of industrial control area requirement, begin to emerge 16bit single chip, but because the price is not ideal did not get very widely. After the 1990s with consumer electronic products development, microcontroller technology has been a tremendous increase. As the INTEL i960 series especially later ARM series widely, 32bit SCM rapidly replacing 16bit single chip of highend status, and into the mainstream market. While the traditional 8 bit microcontroller performance also obtained the rapid increase, processing power than 1980s raised hundreds times. At present, highend 32bit SCM frequency has exceeded 300MHz, performance straight after the middle of 9039。s of dedicated processor, whereas normal type exfactory price dropped to $1, the highestprofile [1] type was only ten dollars. Contemporary SCM system no longer only in LuoJi environment, development and use of special embedded operating system is widely used in the whole range of singlechip microputer. While in as a handheld puters and mobile phones key processing of highen