1、附录2The introduction of MCUA 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
2、 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 b
3、us 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 + externa
4、l 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 IC, Serial P
5、eripheral 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 p
6、roved 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. Manufactu
7、rers 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 C) is a functional computer system.on.a.chip. It contains a processor core, memory, and programmable input/output peripherals.
8、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 fo
9、r 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 elect
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