Lesson 6 Microcontroller Unit 微控制器

Text

A microcontroller (sometimes abbreviated μC or MCU) is a single IC chip that contains the processor, memory, a clock and an I/O control unit[1].

The 8051 is the name of a big family of microcontrollers. The 8051 is an 8-bit microprocessor originally designed in the 1980s by Intel. Its standard form includes several standard on-chip peripherals, including I/O ports, timers, counters, and memory, making single-chip implementations possible.

Its hundreds of derivatives, manufactured by several different companies (like Philips) include even more on-chip peripherals, such as analog-digital converters, pulsewidth modulators, etc.

Atmel fabricated the flash ROM version of 8051[2] which is popularly known as AT89C51 (C in the part number indicates CMOS) . The flash memory can erase the contents within seconds.

The device AT89S52 manufactured by Atmel allows the program memory to be reprogrammed in-system. The architecture of AT89S52 is represented as the figure 2-12.

The 89S52 has 4 ports, each one having 8 input/output lines providing a total of 32 I/O lines [3]. Those ports can be used to output data and orders do other devices[4], or to read the state of a sensor, or a switch. Some of the ports of the 89S52 have dual function meaning that they can be used for two different functions: the first one is to perform input/output operations and the second one is used to implement special features of the microcontroller like counting external pulses, external interrupting[5] (Fig. 2-13) .

There are two different memory types: RAM and Flash ROM. RAM is used to store variable during program execution[6], while ROM is used to store the program. The AT89S52 provides 8K bytes of Flash ROM and 256 bytes of RAM.

The special features of the 89S52 microcontroller are Timers, Counters, Interrupts, Serial port, SFRs (Special Function Register) , and Watch dog.

The CPU (Central Processing Unit) is the heart of the microcontrollers, it is the CPU that will read the program and execute it by interacting with the different peripherals[7].

Microcontrollers were originally programmed only in assembly language, but high-level programming languages such as C programming language are now also in common use to program microcontrollers.

The majority of microcontrollers in use today are embedded in other machinery, such as automobiles, telephones, appliances, and peripherals for computer systems. These are called embedded systems.

New Words and Technical Terms

Notes to the Text

[1]A microcontroller is a single IC chip that contains the processor, memory, a clock and an I/O control unit.：微控制器（单片机）是一个单一集成电路芯片，内部集成了处理器、存储器、时钟和输入/输出控制器。

[2]Atmel fabricated the flash ROM version of 8051：Atmel公司制造了闪速只读存储器版本的8051单片机。

[3]each one having 8 input/output lines providing a total of 32 I/O lines：每一个端口有8路输入/输出线，提供总共32路输入/输出线。

[4]output data and orders do other devices：output在这里是动词，输出数据和命令，控制其他设备。

[5]counting external pulses, external interrupting：对外部脉冲计数，执行外部中断。

[6]store variable during program execution：在程序执行过程中存储变量。

[7]read the program and execute it by interacting with the different peripherals：it代替program。通过与不同的外围设备相互作用，阅读程序并执行程序。

Exercises

Ⅰ.Choose the best technical term to complete the following statements.

1.Like a standard computer, the microcontroller includes a ( ), RAM, ROM, I/O ports, and timers.

A. processor B. CPU C. keyboard D. monitor

2.Typical output devices of a microcontroller include ( ), LEDs, and LCD displays.

A. sensors B. relays C. switches D. radio frequency devices

3.The second function of the MCU ports is used to implement ( ).

A. output data B. read the state of a sensor C. counting pulses D. external interrupting

4.In a microcontroller, ( ) is used to store the program because this kind memory can retain the stored information even when not powered.

A. RAM B. ROM C. Flash ROM D. Register

5.( ) are not the special features of the 89S52 microcontroller.

A. Timers B. Counters C. Serial Ports D. Parallel Ports

6. ( ) are now in common use to program microcontrollers.

A. assembly language B. C language C. BASIC D. VHDL

7.A microcontroller is used inside a system, such as an automobile, ( ) or electronic rice cooker.

A. air conditioner B. lamp C. mobile telephone D. printer

Ⅱ.Translate the following sentences into Chinese.

1.80C51 chips have 128 bytes of RAM and 4KB flash ROM. If necessary, 8051 memory can be expanded up to 128KB by adding external memory.

2.The μVision IDE from Keil combines project management, source code editing, program debugging, and complete simulation in one powerful environment.

3.The machine language basically just zeros and ones and written in hexadecimal format, can be executed by a processor. Keil is a compiler used to convert a high level language, such as C source code to object code.

4.If your microwave oven has an LED or LCD screen and a keypad, it contains a microcontroller.

5.Any device that has a remote control almost certainly contains a microcontroller: TVs, and highend stereo systems all fall into this category.

6.All modern automobiles contain at least one microcontroller, and can have as many as six or seven: The engine is controlled by a microcontroller, as are the anti-lock brakes, the cruise control and so on.