MCU development and application

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

input/output interfaces such as serial ports (UARTs)

other serial communications interfaces like I²C, Serial Peripheral Interface and Controller Area Network for system interconnect peripherals such as timers and watchdog RAM for data storage ROM, EPROM, EEPROM or Flash memory for program storage clock generator - often an oscillator for a quartz timing crystal, resonator or RC circuit many include analog-to-digital converters .

This integration drastically reduces the number of chips and the amount of wiring and PCB space that would be needed to produce equivalent systems using separate chips and have proved to be highly popular in embedded systems since their introduction in the 1970s.

Some microcontrollers can afford to use a Harvard architecture: separate memory buses for instructions and data, allowing accesses to take place concurrently.

The decision of which peripheral to integrate is often difficult. The Microcontroller vendors often trade operating frequencies and system design flexibility against time-to-market requirements from their customers and overall lower system cost. Manufacturers have to balance the need to minimize the chip size against additional functionality.

Microcontroller architectures are available from many different vendors in so many varieties that each instruction set architecture could rightly belong to a category of their own. Chief among these are the 8051, Z80 and ARM derivatives.[citation needed]

A microcontroller (also MCU or µC) is a functional computer

system-on-a-chip. It contains a processor core, memory, and programmable input/output peripherals.

Microcontrollers include an integrated CPU, memory (a small amount of RAM, program memory, or both) and peripherals capable of input and output.

It emphasizes high integration, in contrast to a microprocessor which only contains a CPU (the kind used in a PC). In addition to the usual arithmetic and logic elements of a general purpose microprocessor, the microcontroller integrates additional elements such as read-write memory for data storage, read-only memory for program storage, Flash memory for permanent data storage, peripherals, and input/output interfaces. At clock speeds of as little as 32KHz, microcontrollers often operate at very low speed compared to microprocessors, but this is adequate for typical applications. They consume relatively little power (milliwatts or even microwatts), and will generally have the ability to retain functionality while waiting for an event such as a button press or interrupt. Power consumption while sleeping (CPU clock and peripherals disabled) may be just nanowatts, making them ideal for low power and long lasting battery applications.

Microcontrollers are used in automatically controlled products and devices, such as automobile engine control systems, remote controls, office machines, appliances, power tools, and toys. By reducing the size, cost, and power consumption compared to a design using a separate

microprocessor, memory, and input/output devices, microcontrollers make it economical to electronically control many more processes.

The majority of computer systems in use today are embedded in other machinery, such as automobiles, telephones, appliances, and peripherals for computer systems. These are called embedded systems. While some embedded systems are very sophisticated, many have minimal requirements for memory and program length, with no operating system, and low software complexity. Typical input and output devices include switches, relays,

solenoids, LEDs, small or custom LCD displays, radio frequency devices, and sensors for data such as temperature, humidity, light level etc. Embedded systems usually have no keyboard, screen, disks, printers, or other recognizable I/O devices of a personal computer, and may lack human interaction devices of any kind.

It is mandatory that microcontrollers provide real time response to events in the embedded system they are controlling. When certain events occur, an interrupt system can signal the processor to suspend processing the current instruction sequence and to begin an interrupt service routine (ISR). The ISR will perform any processing required based on the source of the interrupt before returning to the original instruction sequence. Possible interrupt sources are device dependent, and often include events such as an internal timer overflow, completing an analog to digital conversion, a logic level change on an input such as from a button being pressed, and data received on a communication link. Where power consumption is important as in battery operated devices, interrupts may also wake a microcontroller from a low power sleep state where the processor is halted until required to do something by a peripheral event.

Microcontroller programs must fit in the available on-chip program memory, since it would be costly to provide a system with external, expandable, memory. Compilers and assembly language are used to turn high-level language programs into a compact machine code for storage in the microcontroller's memory. Depending on the device, the program memory may be permanent, read-only memory that can only be programmed at the factory, or program memory may be field-alterable flash or erasable read-only memory.

Since embedded processors are usually used to control devices, they sometimes need to accept input from the device they are controlling. This is the purpose of the analog to digital converter. Since processors are

built to interpret and process digital data, i.e. 1s and 0s, they won't be able to do anything with the analog signals that may be being sent to it by a device. So the analog to digital converter is used to convert the incoming data into a form that the processor can recognize. There is also a digital to analog converter that allows the processor to send data to the device it is controlling.

In addition to the converters, many embedded microprocessors include a variety of timers as well. One of the most common types of timers is the Programmable Interval Timer, or PIT for short. A PIT just counts down from some value to zero. Once it reaches zero, it sends an interrupt to the processor indicating that it has finished counting. This is useful for devices such as thermostats, which periodically test the temperature around them to see if they need to turn the air conditioner on, the heater on, etc.

Time Processing Unit or TPU for short. Is essentially just another timer, but more sophisticated. In addition to counting down, the TPU can detect input events, generate output events, and other useful operations.

Dedicated Pulse Width Modulation (PWM) block makes it possible for the CPU to control power converters, resistive loads, motors, etc., without using lots of CPU resources in tight timer loops.

Universal Asynchronous Receiver/Transmitter (UART) block makes it possible to receive and transmit data over a serial line with very little load on the CPU. SCM history

SCM was born in the late 20th century, 70, experienced SCM, MCU, SOC three stages. First model 1.SCM the single chip microcomputer (Single Chip Microcomputer) stage, mainly seeking the best of the best single form of embedded systems

architecture. "Innovation model" success, laying the SCM and general computer completely different path of development. In the open road of independent development of embedded systems, Intel Corporation contributed.

2.MCU the micro-controller (Micro Controller Unit) stage, the main direction of technology development: expanding to meet the embedded applications, the target system requirements for the various peripheral circuits and interface circuits, highlight the object of intelligent control.It involves the areas associated with the object system, therefore, the development of MCU's responsibility inevitably falls on electrical, electronics manufacturers. From this point of view, Intel faded MCU development has its objective factors. In the development of MCU, the most famous manufacturers as the number of Philips Corporation. Philips company in embedded applications, its great advantage, the MCS-51 single-chip micro-computer from the rapid development of the micro-controller. Therefore, when we look back at the path of development of embedded systems, do not forget Intel and Philips in History. Embedded Systems Embedded system microcontroller is an independent development path, the MCU important factor in the development stage, is seeking applications to maximize the solution on the chip; Therefore, the development of dedicated single chip SOC trend of the natural form. As the microelectronics, IC design, EDA tools development, application system based on MCU SOC design have greater development. Therefore, the understanding of the microcontroller chip microcomputer can be, extended to the single-chip micro-controller applications.

MCU applications

SCM now permeate all areas of our lives, which is almost difficult to find traces of the field without SCM. Missile navigation equipment, aircraft,

all types of instrument control, computer network communications and data transmission, industrial automation, real-time process control and data processing, extensive use of various smart IC card, civilian luxury car security system, video recorder, camera, fully automatic washing machine control, and program-controlled toys, electronic pet, etc., which are inseparable from the microcontroller. Not to mention the area of robot control, intelligent instruments, medical equipment was. Therefore, the MCU learning, development and application of the large number of computer applications and intelligent control of the scientists, engineers. SCM is widely used in instruments and meters, household appliances, medical equipment, aerospace, specialized equipment, intelligent management and process control fields, roughly divided into the following several areas: 1. In the application of Intelligent Instruments

SCM has a small size, low power consumption, controlling function, expansion flexibility, the advantages of miniaturization and ease of use, widely used instrument, combining different types of sensors can be realized Zhuru voltage, power, frequency, humidity, temperature, flow, speed, thickness, angle, length, hardness, elemental, physical pressure measurement. SCM makes use of digital instruments, intelligence, miniaturization, and functionality than electronic or digital circuits more powerful. Such as precision measuring equipment (power meter, oscilloscope, various analytical instrument). 2. In the industrial control application

With the MCU can constitute a variety of control systems, data acquisition system. Such as factory assembly line of intelligent control 3. In Household Appliances

can be said that the appliances are basically using SCM, praise from the electric rice, washing machines, refrigerators, air conditioners, color

TV, and other audio video equipment, to the electronic weighing equipment, varied, and omnipresent.

4. In the field of computer networks and communications applications MCU general with modern communication interface, can be easy with the computer data communication, networking and communications in computer applications between devices had excellent material conditions, are basically all communication equipment to achieve a controlled by MCU from mobile phone, telephone, mini-program-controlled switchboards, building automated communications call system, train radio communication, to the daily work can be seen everywhere in the mobile phones, trunked mobile radio, walkie-talkies, etc.. 5. Microcomputer in the field of medical device applications

SCM in the use of medical devices is also quite extensive, such as medical respirator, the various analyzers, monitors, ultrasound diagnostic equipment and hospital beds, etc. call system. 6. In a variety of major appliances in the modular applications Designed to achieve some special single specific function to be modular in a variety of circuit applications, without requiring the use of personnel to understand its internal structure. If music integrated single chip, seemingly simple function, miniature electronic chip in the net (the principle is different from the tape machine), you need a computer similar to the principle of the complex. Such as: music signal to digital form stored in memory (like ROM), read by the microcontroller, analog music into electrical signals (similar to the sound card). In large circuits, modular applications that greatly reduce the volume, simplifies the circuit and reduce the damage, error rate, but also easy to replace.

7. Microcontroller in the application field of automotive equipment SCM in automotive electronics is widely used, such as a vehicle engine

controller, CAN bus-based Intelligent Electronic Control Engine, GPS navigation system, abs anti-lock braking system, brake system, etc.. In addition, the MCU in business, finance, research, education, national defense, aerospace and other fields has a very wide range of applications.

单片机的发展和应用

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（有少量的RAM ，程序存储器，或两者兼而有之）和一个可编程输入/输出外设。

它强调高度集成，而相比之下，一个微处理器只包含一个CPU （比如一台PC ） 。除了通常的算术和逻辑要素等一般用途的微处理器，微控制器还集成了更多的要素，如读写存储器的数据存储，只读存储器的存储程序，快闪记忆体的永久数据存储，外设，和输入/输出接口。在时钟频率只有32Mhz的情况下 ，微操作系统往往以非常低的速度相运行，但是这足够典型的应用。他们消耗较少的功率（毫瓦或什微） ，且具有保持功能，同时可以等待一个事件，如一个按钮的按下或中断。在睡眠状态时， CPU时钟和外设禁用，从而使它们适合用于低功耗和长期持久的电池应用。

微控制器广泛应用于自动控制产品和设备，如汽车发动机控制系统，远程控制系统，办公室机器设备系统，家用电器，电动工具，和玩具等。通过降低尺寸，成本和能耗，设计使用单独的微处理器，内存和输入/输出设备，能够使微控制器控制更多的进程，更经济。

目前，大多数的计算机系统被嵌入在其他设备中使用，如汽车，电话以及很多需要外设的计算机系统。这些嵌入其他设备的计算机系统被称为嵌入式系统。有些嵌入式系统是非常复杂的，很多能够达到人们的要求，但由于内存和程序长度的限制，软件的复杂性降低。典型的输入和输出设备包括交换机，继电器，螺线管，发光二极管，小形或定制的液晶显示器，数码显示器等。射频设备和传感器等嵌入式系统通常没有键盘，屏幕，硬盘，打印机或其他公认的I / O设备，并可能缺乏人机互动装置的任何一种。

某些强制性的微控制器能够提供实时应对突发事件的嵌入式系统并控制它们。当某些事件发生时，中断系统能够让信号处理器暂停处理当前的指令序列，并开始了中断服务。当中断服务结束之后，再返回原来的指令序列，这就是我们通常所说的单片机的中断系统。中断源的设备依赖通常有很多种，如内部定时器

溢、完成了模拟向数字转换、逻辑水平变化的一种投入、一个按钮被按下和收到了数据的通信联系等。凡是许多重要的中断源发出中断申请，都必须中断，如电池供电的设备停止运行后，微控制器在低功耗睡眠状态下的处理器必须停止，直到做一些外围的活动才重新开始返回当前指令序列。

单片机程序必须符合现有的芯片程序存储器的要求，因为这将是代价高昂的系统提供了与外部设备之间可以扩展的存储器。编译器和汇编语言是用来打开高级语言程序到一个紧凑机器代码存储在微控制器的存储过程。根据不同的设备，程式记忆体可能是永久性的，而唯读存储器，只能进行编程。在工厂，可以生产可擦除式只读存储器。

由于嵌入式处理器通常是用来控制设备的，他们有时需要接受输入设备的数据输入，但由于处理器内置处理数数据只有1和0 ，所以它们将无法直接处理任何模拟信号。因此，要先使需要处理的数据通过模拟向数字转换的过程，才能使传入的数据转化为处理器可以识别的形式。还有一种转换器叫做数模转换器，他能够使数字信号转换为模拟信号并将数据发送到需要CPU控制的设备上，以达到控制的目的。

此外，许多嵌入式微处理器包括各种兼职的转换器。最常见的一种类型的转换器是可编程间隔定时转换器。工作过程为一个倒计时刚到达零，它就会对处理器发出一个中断的指令。这表明它已经完成转换，并需要对所控制的设备发出指令，使其作出某些动作。这是非常有用的设备，如恒温系统，需要定期测试他们周围的温度，看看他们是否需要打开空调或者加热器等等。

单片机历史

单片机诞生于20世纪70年代末，经历了SCM、MCU、SoC三大阶段。 起初模型

1.SCM即单片微型计算机（Single Chip Microcomputer）阶段，主要是寻求最佳的单片形态嵌入式系统的最佳体系结构。“创新模式”获得成功，奠定了SCM与通用计算机完全不同的发展道路。在开创嵌入式系统独立发展道路上，Intel公司功不可没。

2.MCU即微控制器（Micro Controller Unit）阶段，主要的技术发展方向是：不断扩展满足嵌入式应用时，对象系统要求的各种外围电路与接口电路，突

显其对象的智能化控制能力。它所涉及的领域都与对象系统相关，因此，发展MCU的重任不可避免地落在电气、电子技术厂家。从这一角度来看，Intel逐渐淡出MCU的发展也有其客观因素。在发展MCU方面，最著名的厂家当数Philips公司。

Philips公司以其在嵌入式应用方面的巨大优势，将MCS-51从单片微型计算机迅速发展到微控制器。因此，当我们回顾嵌入式系统发展道路时，不要忘记Intel和Philips的历史功绩。

嵌入式系统

单片机是嵌入式系统的独立发展之路，向MCU阶段发展的重要因素，就是寻求应用系统在芯片上的最大化解决；因此，专用单片机的发展自然形成了SOC化趋势。随着微电子技术、IC设计、EDA工具的发展，基于SOC的单片机应用系统设计会有较大的发展。因此，对单片机的理解可以从单片微型计算机、单片微控制器延伸到单片应用系统。

单片机的应用领域

目前单片机渗透到我们生活的各个领域，几乎很难找到哪个领域没有单片机的踪迹。导弹的导航装置，飞机上各种仪表的控制，计算机的网络通讯与数据传输，工业自动化过程的实时控制和数据处理，广泛使用的各种智能IC卡，民用豪华轿车的安全保障系统，录像机、摄像机、全自动洗衣机的控制，以及程控玩具、电子宠物等等，这些都离不开单片机。更不用说自动控制领域的机器人、智能仪表、医疗器械了。因此，单片机的学习、开发与应用将造就一批计算机应用与智能化控制的科学家、工程师。

单片机广泛应用于仪器仪表、家用电器、医用设备、航空航天、专用设备的智能化管理及过程控制等领域，大致可分如下几个范畴：

1.在智能仪器仪表上的应用

单片机具有体积小、功耗低、控制功能强、扩展灵活、微型化和使用方便等优点，广泛应用于仪器仪表中，结合不同类型的传感器，可实现诸如电压、功率、频率、湿度、温度、流量、速度、厚度、角度、长度、硬度、元素、压力等物理量的测量。采用单片机控制使得仪器仪表数字化、智能化、微型化，且功能比起采用电子或数字电路更加强大。例如精密的测量设备（功率计，示波器，各种分

析仪）。

2.在工业控制中的应用

用单片机可以构成形式多样的控制系统、数据采集系统。例如工厂流水线的智能化管

3.在家用电器中的应用

可以这样说，现在的家用电器基本上都采用了单片机控制，从电饭褒、洗衣机、电冰箱、空调机、彩电、其他音响视频器材、再到电子秤量设备，五花八门，无所不在。

4.在计算机网络和通信领域中的应用

现代的单片机普遍具备通信接口，可以很方便地与计算机进行数据通信，为在计算机网络和通信设备间的应用提供了极好的物质条件，现在的通信设备基本上都实现了单片机智能控制，从手机，电话机、小型程控交换机、楼宇自动通信呼叫系统、列车无线通信、再到日常工作中随处可见的移动电话，集群移动通信，无线电对讲机等。

5.单片机在医用设备领域中的应用

单片机在医用设备中的用途亦相当广泛，例如医用呼吸机，各种分析仪，监护仪，超声诊断设备及病床呼叫系统等等。

6.在各种大型电器中的模块化应用

某些专用单片机设计用于实现特定功能，从而在各种电路中进行模块化应用，而不要求使用人员了解其内部结构。如音乐集成单片机，看似简单的功能，微缩在纯电子芯片中（有别于磁带机的原理），就需要复杂的类似于计算机的原理。如：音乐信号以数字的形式存于存储器中（类似于ROM），由微控制器读出，转化为模拟音乐电信号（类似于声卡）。

在大型电路中，这种模块化应用极大地缩小了体积，简化了电路，降低了损坏、错误率，也方便于更换。

7.单片机在汽车设备领域中的应用

单片机在汽车电子中的应用非常广泛，例如汽车中的发动机控制器，基于CAN总线的汽车发动机智能电子控制器，GPS导航系统，abs防抱死系统，制动系统等等。

此外，单片机在工商，金融，科研、教育，国防航空航天等领域都有着十分广泛的用途。