通信工程文献翻译——（1）单片机

单片机即单片微型计算机，是把中央处理器、存储器、定时/计数器、输入输出接口都集成在一块集成电路芯片上的微型计算机。与应用在个人电脑中的通用型微处理器相比，它更强调自供应（不用外接硬件）和节约成本。它的最大优点是体积小，可放在仪表内部，但存储量小，输入输出接口简单，功能较低。由于其发展非常迅速，旧的单片机的定义已不能满足，所以在很多应用场合被称为范围更广的微控制器，但是目前在中国大陆仍多沿用“单片机”的称呼。 

绝大多数现在的单片机都是基于冯·诺伊曼结构的，这种结构清楚地定义了嵌入式系统所必需的四个基本部分：一个中央处理器核心，程序存储器（只读存储器或者闪存）、数据存储器（随机存储器），一个或者更多的定时/计时器，还有用来与外围设备以及扩展资源进行通信的输入/输出端口——所有这些都被集成在单个集成电路芯片上。说单片机与通用型中央处理单元芯片不同是因为前者一般很容易配合最小型的外部支持芯片制成工作计算机。这样就可以很容易的把单片机系统植入装置内部来控制装置了。近年来为了在指令和数据上使用不同的字宽，并提高处理器流水线速度，哈佛结构在微控制器和DSP也逐渐得到了广泛的应用。 

传统的微处理器是不允许这么做的。它要完成单片机的工作，就必须连接一些其他芯片。比如说，片上没有数据存储器，就必须要添加一些RAM的存储芯片，虽然所添加存储器的容量很灵活，但是至少还是要添加，另外还需要添加很多连线来传递芯片之间的数据。 比如，一个典型的微控制器只需要一个时钟发生器和很少的RAM和ROM(或者EPROM, E2PROM)就可以在软件和晶振下工作了。同时，微控制器具有丰富的输入输出设备，像是模拟数字转换(ADC)，定时器，串口或者其他串行通讯接口(比如I2C，串行外围接口(SPI),控制器局域网)。通常，这些继承在内部的设备可以通过特殊的指令来操作。 

一些现代的微控制器支持一些内建的高级编程语言，比如BASIC语言。

一个微控制器（也叫MCU）是一个微型计算芯片。它包含一个处理器、一个内存（有.......

（1）MCU

A microcontroller (or MCU) is a computer-on-a-chip. It is a type of microprocessor emphasizing self-sufficiency and cost-effectiveness, in contrast to a general-purpose microprocessor (the kind used in a PC). 

The majority of computer systems in use today are embedded in other machinery, such as telephones, clocks, appliances, vehicles, and infrastructure. An embedded system usually has minimal requirements for memory and program length and may require simple but unusual input/output systems. For example, most embedded systems lack keyboards, screens, disks, printers, or other recognizable I/O devices of a personal computer. They may control electric motors, relays or voltages, and read switches, variable resistors or other electronic devices. Often, the only I/O device readable by a human is a single light-emitting diode, and severe cost or power constraints can even eliminate that. 

In contrast to general-purpose CPUs, microcontrollers do not have an address bus or a data bus, because they integrate all the RAM and non-volatile memory on the same chip as the CPU. Because they need fewer pins, the chip can be placed in a much smaller, cheaper package. 

Integrating the memory and other peripherals on a single chip and testing them as a unit increases the cost of that chip, but often results in decreased net cost of the embedded system as a whole. (Even if the cost of a CPU that has integrated peripherals is slightly more than the cost of a CPU + external peripherals, having fewer chips typically allows a smaller and cheaper circuit board, and reduces the labor required to assemble and test the circuit board). This trend leads to design. 

A microcontroller is a single integrated circuit, commonly with the following features: 

central processing unit - ranging from small and simple 4-bit processors to sophisticated 32- or 64-bit processors ......