【正文】 nciple of MCUSinglechip is an integrated on a single chip a plete puter system. Even though most of his features in a small chip, but it has a need to plete the majority of puter ponents: CPU, memory, internal and external bus system, most will have the Core. At the same time, such as integrated munication interfaces, timers, realtime clock and other peripheral equipment. And now the most powerful singlechip microputer system can even voice, image, networking, input and output plex system integration on a single chip. Also known as singlechip MCU (Microcontroller), because it was first used in the field of industrial control. Only by the singlechip CPU chip developed from the dedicated processor. The design concept is the first by a large number of peripherals and CPU in a single chip, the puter system so that smaller, more easily integrated into the plex and demanding on the volume control devices. INTEL the Z80 is one of the first design in accordance with the idea of the processor, From then on, the MCU and the development of a dedicated processor parted ways. Early singlechip 8bit or all of the four. One of the most successful is INTEL39。s 8031, because the performance of a simple and reliable access to a lot of good praise. Since then in 8031 to develop a singlechip microputer system MCS51 series. Based on singlechip microputer system of the system is still widely used until now. As the field of industrial control requirements increase in the beginning of a 16bit singlechip, but not ideal because the price has not been very widely used. After the 9039。s with the big consumer electronics product development, singlechip technology is a huge improvement. INTEL i960 Series with subsequent ARM in particular, a broad range of applications, quickly replaced by 32bit singlechip 16bit singlechip highend status, and enter the mainstream market. Traditional 8bit singlechip performance has been the rapid increase in processing power pared to the 8039。s to raise a few hundred times. At present, the highend 32bit singlechip frequency over 300MHz, the performance of the mid9039。s close on the heels of a special processor, while the ordinary price of the model dropped to one . dollars, the most highend models, only 10 . dollars. Contemporary singlechip microputer system is no longer only the baremetal environment in the development and use of a large number of dedicated embedded operating system is widely used in the full range of singlechip microputer. In PDAs and cell phones as the core processing of highend singlechip or even a dedicated direct access to Windows and Linux operating systems. More than a dedicated singlechip processor suitable for embedded systems, so it was up to the application. In fact the number of singlechip is the world39。s largest puter. Modern human life used in almost every piece of electronic and mechanical products will have a singlechip integration. Phone, telephone, calculator, home appliances, electronic toys, handheld puters and puter accessories such as a mouse in the Department are equipped with 12 single chip. And personal puters also have a large number of singlechip microputer in the workplace. Vehicles equipped with more than 40 Department of the general singlechip, plex industrial control systems and even singlechip may have hundreds of work at the same time! SCM is not only far exceeds the number of PC and other integrated puting, even more than the number of human beings.Hardwave introductionThe 8051 family of micro controllers is based on an architecture which is highly optimized for embedded control systems. It is used in a wide variety of applications from military equipment to automobiles to the keyboard on your PC. Second only to the Motorola 68HC11 in eight bit processors sales, the 8051 family of microcontrollers is available in a wide array of variations from manufacturers such as Intel, Philips, and Siemens. These manufacturers have added numerous features and peripherals to the 8051 such as I2C interfaces, analog to digital converters, watchdog timers, and pulse width modulated outputs. Variations of the 8051 with clock speeds up to 40MHz and voltage requirements down to volts are available. This wide range of parts based on one core makes the 8051 family an excellent choice as the base architecture for a pany39。s entire line of products since it can perform many functions and developers will only have to learn this one platform. The basic architecture consists of the following features: an eight bit ALU 32 descrete I/O pins (4 groups of 8) which can be individually accessed two 16 bit timer/counters full duplex UART 6 interrupt sources with 2 priority levels 128 bytes of on board RAM separate 64K byte address spaces for DATA and CODE memoryOne 8051 processor cycle consists of twelve oscillator periods. Each of the twelve oscillator periods is used for a special function by the 8051 core such as op code fetches and samples of the interrupt daisy chain for pending interrupts. The time required for any 8051 instruction can be puted by dividing the clock frequency by 12, inverting that result and multiplying it by the number of processor cycles required by the instruction in question. Therefore, if you have a system which is using an clock, you can pute the number of instructions per second by dividing this value by 12. This gives an instruction frequency of 921583 instructions per second. Inverting this will provide the amount of time taken by each instruction cycle ( microseconds).40