【正文】 of good 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 microcontroller0, 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 has been the rapid increase capacity increase pared to 80 the number of times. Currently, highend 32bit microcontroller clocked over 300MHz, the performance catching the mid90’s dedicated processor, while the average model prices fall to one dollar, the most highend model only 10 dollars. Modern SCM systems are no longer only in the development and use of bare mental 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.More than a dedicated MCU processor suitable for embedded systems, so it was up to the application. In fact the number of SCM is the world’s largest puter. Modern human life used in almost every piece of electronic and mechanical products will be integrated single chip. Phone, telephone, calculator, home appliances, electronic toys, handheld puters and puter accessories such as a mouse with a 12 in both the Department of SCM. Personal puter will have a large number of SCM in the work. General car with more than 40 SCM, plex industrial control systems may even have hundreds of SCM in the same time work! SCM is not only far exceeds the number of PC and other puting the sum, or even more than the number of human beings.An onechip puter system is made up of several following parts: (1)One microprocessor of 8(CPU). (2)At slice data memory RAM(128/256B), it use not depositing not can reading/data that write, such as result not middle of operation, final result and data wanted to show, etc.(3)Procedure memory ROM/EPROM(4KB/8KB), is used to preserve the procedure, some initial data and form in slice. But does not take ROM/EPROM within some onechip puters, such as 8031,8032,80C,etc..(4)Four 8 run side by side I/O interface P0 four P3,each mouth can use as introduction, may use as exporting too.(5)Two timer/counter, each timer/counter may set up and count in the way, used to count to the external incident, can set up into a timing way too, and can according to count or result of timing realize the control of the puter. (6) Five cut off cutting off the control system of the source. (7) One all duplexing serial I/O mouth of UART(universal asynchronous receiver/transmitter(UART)), is it realize onechip puter or onechip puter and serial munication of puter to use for.(8)Stretch oscillator and clock produce circuit, quartz crystal finely tune electric capacity need outer. Allow oscillation frequency as 12 MHz now at most. Every the abovementioned part was joined through the inside data bus. Among them, CPU is a core of the onechip puter, it is the control of the puter and mand centre, made up of such part as arithmetic unit and controller, etc. The arithmetic unit can carry on 8 persons of arithmetic operation and unit ALU of logic operation while including one, the 1 storing device temporarilies of 8,storing device 2 temporarily,8’s accumulation device ACC, register B and procedure state register PSW, etc. Person who accumulate ACC count by 2 input ends entered of checking etc. temporarily as one operation often, e from person who store 1 operation is it is it make operation to go on to count temporarily, operation result and loopback ACC with another one. In addition, ACC is often regarded as the transfer station of data transmission on 8051 inside. The same as general microprocessor, it is the busiest register. Help remembering that agreeing with A expresses in the order. The controller includes the procedure counter, the order is deposited, the order decipher, the oscillator and timing circuit, etc. The procedure counter is made up of counter of 8 for two, amounts to is a byte address counter of the procedure in fact, the content is the next IA that will carried out in PC. The content which changes it can change the direction that the procedure carries out. Shake the circuit in 8051 onechip puters, only need outer quartz crystal and frequency to finely tune the electric capacity, its frequency range is its 12MHZ of , This pulse signal, as 8051 basic beats of working, namely the minimum unit of is the same as other puters, the work in harmony under the control of the basic beat, just like an orchestra according to the beat play that is manded.There are ROM (procedure memory, can only read) and RAM in 8051 slices(data memory, can is it can write) two to read, they have each independent memory address space, dispose way to be the same with general memory of puter. Procedure 8051 memory and 8751 slice procedure memory capacity 4KB, address begin from 0000H, used for preserving the procedure and form constant. Data 80518751 8031 of memory data memory 128B, address false 00FH, use for middle result to deposit operation, the data are stored temporarily and the data are buffered etc.. In RAM of this 128B,there is unit of 32 byte that can be appointed as the job register, this and general microprocessor is diffent,8051 slice RAM and job register rank one formation the same to arrange the location. It is not very the same that the memory of MCS51 series onechip puter and general puter diposes the way in addition. General puter for first address space, ROM and RAM can arrange in different space within the range of this address at will, namely the addresses of ROM and RAM, with distributing differe