单片机是指一个集成在一块芯片上的完整计算机系统。尽管他的大部分功能集成在一块小芯片上,但是它具有一个完整计算机所需要的大部分部件:CPU、内存、内部和外部总线系统,目前大部分还会具有外存。同时集成诸如通讯接口、定时器,实时时钟等外围设备。而现在最强大的单片机系统甚至可以将声音、图像、网络、复杂的输入输出系统集成在一块芯片上。
单片机也被称为微控制器(Microcontroller),是因为它最早被用在工业控制领域。单片机由芯片内仅有CPU的专用处理器发展而来。最早的设计理念是通过将大量外围设备和CPU集成在一个芯片中,使计算机系统更小,更容易集成进复杂的而对体积要求严格的控制设备当中。INTEL的Z80是最早按照这种思想设计出的处理器,从此以后,单片机和专用处理器的发展便分道扬镳。
早期的单片机都是8位或4位的。其中最成功的是INTEL的8031,因为简单可靠而性能不错获得了很大的好评。此后在8031上发展出了MCS51系列单片机系统。基于这一系统的单片机系统直到现在还在广泛使用。随着工业控制领域要求的提高,开始出现了16位单片机,但因为性价比不理想并未得到很广泛的应用。90年代后随着消费电子产品大发展,单片机技术得到了巨大的提高。随着INTEL i960系列特别是后来的ARM系列的广泛应用,32位单片机迅速取代16位单片机的高端地位,并且进入主流市场。而传统的8位单片机的性能也得到了飞速提高,处理能力比起80年代提高了数百倍。目前,高端的32位单片机主频已经超过300MHz,性能直追90年代中期的专用处理器,而普通的型号出厂价格跌落至1美元,最高端的型号也只有10美元。当代单片机系统已经不再只在裸机环境下开发和使用,大量专用的嵌入式操作系统被广泛应用在全系列的单片机上。而在作为掌上电脑和手机核心处理的高端单片机甚至可以直接使用专用的Windows和Linux操作系统。
单片机比专用处理器更适合应用于嵌入式系统,因此它得到了最多的应用。事实上单片机是世界上数量最多的计算机。现代人类生活中所用的几乎每件电子和机械产品中都会集成有单片机。手机、电话、计算器、家用电器、电子玩具、掌上电脑以及鼠标等电脑配件中都配有1-2部单片机。而个人电脑中也会有为数不少的单片机在工作。汽车上一般配备40多部单片机,复杂的工业控制系统上甚至可能有数百台单片机在同时工作!单片机的数量不仅远超过PC机和其他计算的综合,甚至比人类的数量还要多。Single-chip is an integrated on a single chip a complete computer system. Even though most of his features in a small chip, but it has a need to complete the majority of computer components: CPU, memory, internal and external bus system, most will have the Core. At the same time, such as integrated communication interfaces, timers, real-time clock and other peripheral equipment. And now the most powerful single-chip microcomputer system can even voice, image, networking, input and output complex system integration on a single chip.
Also known as single-chip MCU (Microcontroller), because it was first used in the field of industrial control. Only by the single-chip CPU chip developed from the dedicated processor. The design concept is the first by a large number of peripherals and CPU in a single chip, the computer system so that smaller, more easily integrated into the complex and demanding on the volume control devices. INTEL the Z80 is one of the first design in accordance with the idea of the processor, From then on, the MCU and the development of a dedicated processor parted ways.
Early single-chip 8-bit or all of the four. One of the most successful is INTEL's 8031, because the performance of a simple and reliable access to a lot of good praise. Since then in 8031 to develop a single-chip microcomputer system MCS51 series. Based on single-chip microcomputer system of the system is still widely used until now. As the field of industrial control requirements increase in the beginning of a 16-bit single-chip, but not ideal because the price has not been very widely used. After the 90's with the big consumer electronics product development, single-chip technology is a huge improvement. INTEL i960 Series with subsequent ARM in particular, a broad range of applications, quickly replaced by 32-bit single-chip 16-bit single-chip high-end status, and enter the mainstream market. Traditional 8-bit single-chip performance has been the rapid increase in processing power compared to the 80's to raise a few hundred times. At present, the high-end 32-bit single-chip frequency over 300MHz, the performance of the mid-90's close on the heels of a special processor, while the ordinary price of the model dropped to one U.S. dollars, the most high-end models, only 10 U.S. dollars. Contemporary single-chip microcomputer system is no longer only the bare-metal environment in the development and use of a large number of dedicated embedded operating system is widely used in the full range of single-chip microcomputer. In PDAs and cell phones as the core processing of high-end single-chip or even a dedicated direct access to Windows and Linux operating systems.
More than a dedicated single-chip processor suitable for embedded systems, so it was up to the application. In fact the number of single-chip is the world's largest computer. Modern human life used in almost every piece of electronic and mechanical products will have a single-chip integration. Phone, telephone, calculator, home appliances, electronic toys, handheld computers and computer accessories such as a mouse in the Department are equipped with 1-2 single chip. And personal computers also have a large number of single-chip microcomputer in the workplace. Vehicles equipped with more than 40 Department of the general single-chip, complex industrial control systems and even single-chip may have hundreds of work at the same time! SCM is not only far exceeds the number of PC and other integrated computing, even more than the number of human beings.
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