【導(dǎo)讀】寫MCU表示單片機(jī)，它最早是被用在工業(yè)控制領(lǐng)域。單片機(jī)由芯片內(nèi)僅有。CPU的專用處理器發(fā)展而來。最早的設(shè)計(jì)理念是通過將大量外圍設(shè)備和。積要求嚴(yán)格的控制設(shè)備當(dāng)中。早期的單片機(jī)都是8位或4位的。其中最成功的是INTEL的8031，因。為簡(jiǎn)單可靠而性能不錯(cuò)獲得了很大的好評(píng)。此后在8031上發(fā)展出了MCS51. 基于這一系統(tǒng)的單片機(jī)系統(tǒng)直到現(xiàn)在還在廣泛使用。想并未得到很廣泛的應(yīng)用。90年代后隨著消費(fèi)電子產(chǎn)品大發(fā)展，單片機(jī)技。術(shù)得到了巨大提高。隨著INTELi960系列特別是后來的ARM系列的廣泛。應(yīng)用，32位單片機(jī)迅速取代16位單片機(jī)的高端地位，并且進(jìn)入主流市場(chǎng)。目前，高端的32位單片機(jī)主頻已經(jīng)超過300MHz，性能直追90. 的型號(hào)也只有10美元。機(jī)的數(shù)量不僅遠(yuǎn)超過PC機(jī)和其他計(jì)算的總和，甚至比人類的數(shù)量還要多。作為控制部分的核心部件。因此，發(fā)展MCU的重任不可避免地落在電氣、電子技術(shù)廠家。來看，Intel逐漸淡出MCU的發(fā)展也有其客觀因素。形成了SOC化趨勢(shì)。SOC的單片機(jī)應(yīng)用系統(tǒng)設(shè)計(jì)會(huì)有較大的發(fā)展。

　　

【正文】 hey need to connect on a lot, as if still analog circuit like the microprocessor and devices in the connection between the individual, the number of lines will be a little more surprising, therefore the introduction of the microprocessor bus Zhong Each device Gongtong access connections, all devices 8 Shuju line all received eight public online, that is the equivalent of all devices together in parallel, but only this does not work, if there are two devices send data at the same time, a 0, a 1, then, whether the receiver received what is it? This situation is not allowed, so to be controlled by controlling the line, timesharing the device to work at any time only one device to send data (which can have multiple devices to receive both). Device39。s data connection is known as the data bus, the device is called line of control all the control bus. Internal or external memory in the microcontroller and other devices have memory cells, the memory cell to be assigned addresses, you can use, distribution, of course, to address given in the form of electrical signals, and as more memor y cells, so, for the address allocation The line is also more of these lines is called the address bus. Second, data, address, mand The reason why these three together because of the nature of these three are the same the number, or are a string of 39。0 39。and 39。139。 form the sequence. In other words, addresses, instructions are also data. Instruction: from single chip designer provides a number of monly used instructions with mnemonic we have a strict correspondence between the developer can not be change d by the MCU. Address: the search for MCU internal, external storage units, input and output port based on the address of the internal unit value provided by the chip designer is good, can not be changed, the external unit can be single chip developers to decide, but there are a number of address units is a must (see procedures for the implementation of the process). Third, P0 port, P2 and P3 of the second function I use: Beginners often on the P0 port, P2 and P3 port I use the second function puzzled that the second function and have a switch between the original function of the process, or have a directive, in fact, the port The second feature is automatic, do not need instructions to convert. Such as , respectively WR, RD signal, when the microchip processing machines external RAM or external I / O port, they are used as a second function, not as a generalpurpose I / O port used, so long as a A microprocessor implementation of the MOVX instruction, there will be a corresponding signal sent from the or , no prior use of mands. In fact 39。not as a generalpurpose I / O port use39。 is also not a 39。no39。 but (user) 39。not39。 as a general purpose I / O port to use. You can arrange the order of a SETB 39。s instructions, and when the MCU execution to the instruction, the also make into a high, but users will not do so because this is usually will cause the system to collapse. Fourth, the program39。s implementation: Reduction in power after the 8051 microcontroller within the program counter (PC) in the value of 0000 39。, the process is always from the 000039。 units started, that is: the system must exist in ROM 0000 39。this unit , and in 0000 39。unit must be stored in a single instruction. 5, the stack: Stack is a region, is used to store data, there is no special about the region itself is a part of internal RAM, special access to its data storage and the way that the socalled 39。advanced post out backward first out 39。, and the stack has a special data transmission instructions that39。 PUSH 39。and39。 POP 39。, has a special expertise in its services unit, that is, the stack pointer SP, whenever a PUSH instruction execution, SP on (in the Based on the original value) automatically add 1, whenever the implementation of a POP instruction, SP will (on the basis of the original value) automatically by 1. As the SP values can be changed with the instructions, so long as the beginning of the process to change the value of the SP, you can set the stack memory unit required, such as the program begins, with an MOV SP, 5FH instructions When set on the stack starting from the memory unit 60H unit. There is always the beginning of the general procedure with such a directive to set the stack pointer, because boot, SP initial value of 07H, 08H This unit from the beginning to stack next, and 08H to 1FH 8031 is the second in the region, three or four working register area, often used, this will lead to confusion of data. Different authors when writing programs, initialize the stack is not exactly the same directive, which i s the author39。s habit. When set up the stack zone, does not mean that the region bee a special memory, it can still use the same memory region as normal, but generally the programmer does not regard it as an ordinary memory used.