【正文】 so that smaller, more easily integrated into the plex and demanding with regard to the reference control devices. INTEL the Z80 is one of the earliest in accordance with this idea to design the processor, From then on, the MCU and the development of a dedicated processor parted ways. Early singlechip 8bit or all of four. One of the most successful are Intel39。s with the big consumer electronics product development, singlechip technology has been enormous improve. With INTEL i960 series, especially the later series of widely used ARM, 32bit singlechip 16bit singlechip microputer rapidly replacing highend status, and enter the mainstream market. Whereas the traditional 8bit MCU performance has been the rapid increase in processing power pared to the 8039。s dedicated processor, while the general model exfactory price dropped to one . dollars, the most highend models, only 10 . dollars. Contemporary singlechip microputer system is no longer only in the baremetal environment development and use of a large number of dedicated embedded operating system is widely used in on a full range of singlechip microputer. In the cell phone as a handheld puter and deal with highend singlechip core can even direct the use of a dedicated Windows and Linux operating systems. Singlechip 8051 CPU by the operator and controller. Calculator to plete the binary arithmetic/logic operations Parts ALU at the core, together with registers on TMP, accumulator ACC, register B, the procedure register PSW status symbol and Boolean processor. Accumulator ACC is an eight registers, which are the most frequent job of CPU registers. In arithmetic, logic operations, the accumulator ACC is often a temporary one at preputing operands (such as being summand), and puting and then save the results (such as algebra and). Register B mainly used for multiplication and division operations. PSW register is also a mark of eight registers, used to store the results of some of the characteristics of puting, if not binary, and so on, and borrow. Its specific meaning of each are shown below. PSW CY AC FO RS1 RS0 OVP to users, the most concerned about are the following four. First of all, the binary symbol CY (PSW7). Whether or not it has express a binary operator (or borrow bits). If the operation results at the highest level there is binary (addition) or borrow (subtraction), the bit is 1, otherwise to 0. Secondly, auxiliary binary symbol AC. Also known as semibinary logo, it reflects both the number eight puting whether there is a half low of four binary, that is, the sum of the four low (or minus) has not binary (or borrow), and if there is AC for one status, otherwise to 0. Third, the overflow flag OV. MCS1 to reflect the number of operator symbols with the results of whether there is any spill, there is spill, this bit is 1, otherwise to 0. Fourth, the parity symbol P. Reflect the content of accumulator ACC parity, if the ACC in an operation that results in evennumbered months have one (such as 11001100B, one of four there is one), then P is 0, otherwise, P = 1. PSW other places, will introduce at a later time. PSW stored procedures because of the status, it is also called the program status character have a calculator in bitwise (bit) to carry out logic operations logic processor (also known as Boolean processor). Its function in the introduction explainbit instruction. About the controller, CPU controller is the nerve center, which includes the timing control logic circuit, an instruction register, decoder, address pointer DPTR and the program counter PC, stack pointer SP and so on. This program counter PC is 16bit register consisting of counters. To singlechip implementation of a program, it is necessary to put the program into memory in advance in order ROM of an area. Single chip action should be taken out of a sequence of mands to be implemented. Therefore, we must have a circuit to find out where the mand module address, the circuit is the program counter PC. When beginning the implementation of singlechip program, to the PC load instructions where the first address, it took out one of each mand (such as for multibyte instructions, each took out a mand byte), PC will automatically add the contents of one to point to the next instruction address, so that instruction can be the order of implementation. Only when the process encountered in the transfer of instructions, subroutine call instructions, or encountered failure (after the introduction), PC only needed to go to go places. 8051 CPU39。 and ADD is the English word, which means the sum. Therefore, users have some knowledge of English to grasp the meaning of singlechip instruction are more convenient. Operand has a wide range of express law, such as more than a few 20H is called immediately, namely, 20H operand is true. And 70H is the memory address of a unit in the unit, placed operand (for example, are 3AH), ADD A, 70H instead of 70H and add the contents of A, but from memory 70H unit 3AH will remove the content and the sum of A. By up, we can see that the actual operation to find a few, and sometimes have to turn a corner, and even turn some bends, this process is known as addressable, MCS51 a total of seven kinds of addressing, are presented below: First, immediately addressing: operand writing in the directive on, and on the procedures with opcode in memory. Put is placed immediately in front of a few to express the way for addressing the immediate addressing, such as 20H. Second, register addressing: operand on the register, in the directive to register the name directly to express operand address. For example, MOV A, R0 to belong to register addressing, the contents of register R0 is about to accumulator A Medium. Third, directly addressing: operand MCU internal RAM on a unit, in the instruc