单片机毕业设计外文文献翻译

英文原文：
80C51
8051 single-chip micro-computer, referred to as microcontrollers, there are known as micro-controller, a micro-computer re -
To branch. SCM is developed in the mid 70s a large-scale integrated circuit chip, a CPU, RAM, ROM, I / O interfaces and interrupt system on the same silicon device. Since the 80s, Microcontroller rapid development, all kinds of new products are constantly emerging, there have been many high-performance of new models now become the field of factory automation and control of the pillar industries.
Pin Function:
MCS-51 is a standard 40-pin DIP IC chip, pin distribution ---- microcontroller pin diagram please refer to:
P0.0 ~ P0.7 P0 port 8-bit bidirectional port lines (in the pin 39 to No. 32 terminal). P1.0 ~ P1.7 P1 port 8-bit bidirectional port line (pin 1 in the No. 8 terminal).
P2.0 ~ P2.7 P2 port 8-bit bidirectional port lines (in the pin terminal 21 ~ 28).
P3.0 ~ P3.7 P3 port 8-bit bidirectional port lines (in the pin terminal 10 ~ 17).
This four I / O port has not exactly the same function, we can get to learn, and other books though, but written in too deep, difficult to understand for beginners, here are according to my own expression to write the I believe that you can understand.
P0 port has three functions:
1, external expansion memory, as the data bus (Figure 1 in D0 ~ D7 of data bus interface)
2, external expansion memory, as the address bus (Figure 1 in A0 ~ A7 to address bus interface)
3, is not extended, it can do a general I / O to use, but within the supreme pull-up resistor, as an input or output should be connected to an external pull-up resistor.
P1 port Zhizuo I / O port to use: its internal pull-up resistor.
P2 port has two functions:
1,An extended external memory when used as an address bus
2, doing a general I / O port used, and their internal pull-up resistor;
P3 port has two functions:
As well as I / O using the external (the internal pull-up resistor), there are some special features, from a special register to set the specific features please refer to our explanation behind the pin.
Internal EPROM of the microcontroller chip (for example, 8751), for the writing process required to provide specialized programming and programming pulse power, these signals are also provided in the form from the signal pin, and Namely: programming pulse: 30 feet (ALE / PROG)
Programming voltage (25V): 31 feet (EA / Vpp)
In introducing the four I / O port referred to a "pull-up resistor" Then, pull-up resistor is what Dongdong do? What role does he play? Said the resistance that is of course, is a resistor, when as an input, the pull-up resistor pulled its potential, if the input is low you can provide a current source; Therefore, if the P0 port as long as the input, in the high impedance state, only an external pull-up resistor to be effective. ALE / PROG address latch control signal: in a system is extended, ALE is used to control the P0 port output low 8-bit address latch latch get together in order to achieve low address and data segregation. (In the back on the expansion of the curriculum, we will see the 8051 expansion of EEPROM circuit, the ALE and the 74LS373 in Figure G-latches connected to the external CPU to access when the time to lock the address low address, the P0 port output. ALE may be high may also be low, when the ALE is high, allowing address latch signal when accessing external memory, ALE signals a negative transition (from positive to negative) P0 port on the lower eight address signals into the latch. when ALE is low, when, P0 port on the content and the output latch line. on the latch, and we will be introduced later.
In the absence of access to external memory during the period, ALE 1 / 6 oscillator frequency output cycle (ie, frequency of 6 points), when access to external memory to 1 / 12 oscillator cycle, the output (12 min frequency). From here we can see that when the system does not extend when the ALE will be 1 / 6 cycle, fixed frequency oscillator output, so can be used as an external clock, or the use of an external timing pulse.
PORG pulse input for the program: In the fifth lesson MCU's internal structure and composition, we know that in 8051 within the a 4KB or 8KB of program memory (ROM), ROM's role is to be used to store user needs implementation of the program, then we are into how to write good programs into this ROM in it? Is actually programmed into the pulse input can be written, this pulse input port is PROG. PSEN external program memory read strobe: In reading an external ROM, PSEN low effective, in order to achieve an external ROM module read.
1, the internal ROM reading, PSEN is not action;
2, external ROM reading at each machine cycle will move twice;
3, external RAM read, the two PSEN pulse is skipped will not be output;
4, external ROM, and ROM-foot-phase OE.
See Figure 2 - (8051 extension 2KB EEPROM circuit in Figure PSEN and expansion ROM in the OE pin-phase)
EA / VPP access and sequence memory control signals
1, then high time:
CPU reads the internal program memory (ROM)
Expansion of the external ROM: When reading the internal program memory than
0FFFH (8051) 1FFFH (8052) automatically reads the external ROM.
2, then low when: CPU to read external program memory (ROM). In the previous study, we are aware, there is no internal ROM MCU 8031, then 8031 microcontroller in the application, this pin is a low level of direct.
3,8751 Shaoxie internal EPROM, to make use of this pin input voltage of 21V for
Shao Xie.
RST Reset signal: when the input signal continuously high for more than two machine cycles when it is effective to complete the MCU reset initialization, when the reset program counter PC = 0000H, ie, after reset from the program memory of the 0000H unit to read the first script.
External crystal oscillator pins XTAL1 and XTAL2. When using the chip internal clock, this two-pin for external quartz crystal and fine-tuning capacitor; when using an external clock, used to access an external clock pulse signal.
VCC: Power Supply +5 V input
VSS: GND Ground.
A VR and the pic are 8051 different structures with 8-bit microcontrollers, because structure is different, so assembly instructions are different, but distinct from the use
of CISC instruction set of the 8051, they are RISC instruction set, and only a few dozen instructions, most instructions are single instruction cycle instruction, so in the same crystal frequency, faster than the 8051. Another PIC 8-bit microcontroller in previous years, is the world's largest MCU shipments, followed by Freescale microcontroller.
ARM is actually 32-bit microcontroller, its internal resources (registers and peripheral functions) than in 8051 and PIC, A VR should be a lot more, with the computer's CPU chip is very close. Commonly used in mobile phones, routers and so on.
DSP is actually a special kind of microcontroller, which from 8-32 are available here. It is specifically used to calculate the digital signals. Operation in some formulas, it's fastest computers than the current home of the CPU even faster. For example, the general 32-bit DSP instruction cycle in an op-End a 32-digit x 32-digit product coupled with a 32-digit. Applied to certain pairs of real-time processing requirements of the higher places
中文译文：
8051
单片微型计算机简称为单片机，又称为微型控制器，是微型计算机的一个重要分支。

单片机是70年代中期发展起来的一种大规模集成电路芯片，是CPU、RAM、ROM、I/O接口和中断系统于同一硅片的器件。

80年代以来，单片机发展迅速，各类新产品不断涌现，出现了许多高性能新型机种，现已逐渐成为工厂自动化和各控制领域的支柱产业之一。

引脚功能：
MCS-51是标准的40引脚双列直插式集成电路芯片，引脚分布请参照----单片机引脚图：
P0.0~P0.7 P0口8位双向口线（在引脚的39~32号端子）。

P1.0~P1.7 P1口8位双向口线（在引脚的1~8号端子）。

P2.0~P2.7 P2口8位双向口线（在引脚的21~28号端子）。

P3.0~P3.7 P3口8位双向口线（在引脚的10~17号端子）。

这4个I/O口具有不完全相同的功能，大家可得学好了，其它书本里虽然有，但写的太深，初学者很难理解，这里都是按我自已的表达方式来写的，相信你也能够理解。

P0口有三个功能：
1、外部扩展存储器时，当做数据总线（如图1中的D0~D7为数据总线接口）
2、外部扩展存储器时，当作地址总线（如图1中的A0~A7为地址总线接口）
3、不扩展时，可做一般的I/O使用，但内部无上拉电阻，作为输入或输出时应在外部接上拉电阻。

P1口只做I/O口使用：其内部有上拉电阻。

P2口有两个功能：
1、扩展外部存储器时，当作地址总线使用
2、做一般I/O口使用，其内部有上拉电阻；
P3口有两个功能：
除了作为I/O使用外（其内部有上拉电阻），还有一些特殊功能，由特殊寄存器来设置，具体功能请参考我们后面的引脚说明。

有内部EPROM的单片机芯片（例如8751），为写入程序需提供专门的编程脉冲和编程电源，这些信号也是由信号引脚的形式提供的，即：编程脉冲：30脚（ALE/PROG）编程电压（25V）：31脚（EA/Vpp）（注：这些引脚的功能应用，除9脚的第二功能外，在“新动力2004版”学习套件中都有应用到。

）在介绍这四个I/O口时提到了一个“上拉电阻”那么上拉电阻又是什么呢？他起什么作用呢？都说了是电阻那当然就是一个电阻啦，当作为输入时，上拉电阻将其电位拉高，若输入为低电平则可提供电流源；所以如果P0口如果作为输入时，处在高阻抗状态，只有外接一个上拉电阻才能有效。

ALE/PROG 地址锁存控制信号：在系统扩展时，ALE用于控制把P0口的输出低8位地址送锁存器锁存起来，以实现低位地址和数据的隔离。

（在后面关于扩展的课程中我们就会看到8051扩展EEPROM电路，在图中ALE与74LS373锁存器的G相连接，当CPU 对外部进行存取时，用以锁住地址的低位地址，即P0口输出。

ALE有可能是高电平也有可能是低电平，当ALE是高电平时，允许地址锁存信号，当访问外部存储
器时，ALE信号负跳变（即由正变负）将P0口上低8位地址信号送入锁存器。

当ALE是低电平时，P0口上的内容和锁存器输出一致。

关于锁存器的内容，我们稍后也会介绍。

在没有访问外部存储器期间，ALE以1/6振荡周期频率输出（即6分频），当访问外部存储器以1/12振荡周期输出（12分频）。

从这里我们可以看到，当系统没有进行扩展时，ALE会以1/6振荡周期的固定频率输出，因此可以做为外部时钟，或者外部定时脉冲使用。

PORG为编程脉冲的输入端：在第五课单片机的内部结构及其组成中，我们已知道，在8051单片机内部有一个4KB或8KB的程序存储器（ROM），ROM 的作用就是用来存放用户需要执行的程序的，那么我们是怎样把编写好的程序存入进这个ROM中的呢？实际上是通过编程脉冲输入才能写进去的，这个脉冲的输入端口就是PROG。

PSEN 外部程序存储器读选通信号：在读外部ROM时PSEN低电平有效，以实现外部ROM单元的读操作。

1、内部ROM读取时，PSEN不动作；
2、外部ROM读取时，在每个机器周期会动作两次；
3、外部RAM读取时，两个PSEN脉冲被跳过不会输出；
4、外接ROM时，与ROM的OE脚相接。

参见图2—（8051扩展2KB EEPROM电路，在图中PSEN与扩展ROM的OE脚相接）
EA/VPP 访问和序存储器控制信号
1、接高电平时：
CPU读取内部程序存储器（ROM）
扩展外部ROM：当读取内部程序存储器超过0FFFH（8051）1FFFH（8052）时自动读取外部ROM。

2、接低电平时：CPU读取外部程序存储器（ROM）。

在前面的学习中我们已知道，8031单片机内部是没有ROM的，那么在应用8031单片机时，这个脚是一直接低电平的。

3、8751烧写内部EPROM时，利用此脚输入21V的烧写电压。

RST 复位信号：当输入的信号连续2个机器周期以上高电平时即为有效，用以完成单片机的复位初始化操作，当复位后程序计数器PC=0000H，即复位后将从程序存储器的0000H单元读取第一条指令码。

XTAL1和XTAL2 外接晶振引脚。

当使用芯片内部时钟时，此二引脚用于外接石英晶体和微调电容；当使用外部时钟时，用于接外部时钟脉冲信号。

VCC：电源+5V输入
VSS：GND接地。

AVR和pic都是跟8051结构不同的8位单片机，因为结构不同，所以汇编指令也有所不同，而且区别于使用CISC指令集的8051,他们都是RISC指令集的，只有几十条指令，大部分指令都是单指令周期的指令，所以在同样晶振频率下，较8051速度要快。

另PIC的8位单片机前几年是世界上出货量最大的单片机，飞思卡尔的单片机紧随其后。

ARM实际上就是32位的单片机，它的内部资源（寄存器和外设功能）较8051和PIC、AVR都要多得多，跟计算机的CPU芯片很接近了。

常用于手机、路由器等等。

DSP其实也是一种特殊的单片机，它从8位到32位的都有。

它是专门用来计算数字信号的。

在某些公式运算上，它比现行家用计算机的最快的CPU还要快。

比如说一般32位的DSP能在一个指令周期内运算完一个32位数乘32位数积再加一个32位数，应用于某些对实时处理要求较高的场合。