【導(dǎo)讀】片機(jī)的應(yīng)用則起到了舉足輕重的作用。單片機(jī)又稱單片微控制器，就是把一個計算機(jī)系。統(tǒng)集成到一個芯片上。它完整地包含了計算機(jī)內(nèi)部的CPU、程序存。儲器、數(shù)據(jù)存儲器、輸入輸出端口等。雖然它的運算速度無法和計算機(jī)相比，但在一些實際的控制應(yīng)用場合已經(jīng)足夠使用了。為了能精確地測量轉(zhuǎn)速，還要保證測量的實時性，要求能測得瞬時轉(zhuǎn)速。集脈沖信號，通過定時計數(shù)算法程序，將轉(zhuǎn)速結(jié)果實時顯示出來。為機(jī)械式定時計數(shù)法和電子式定時計數(shù)法。的測速器是利用置于旋轉(zhuǎn)體內(nèi)的放射性材料來發(fā)生脈沖信號。光電式，光電式測系統(tǒng)具有低慣性、低噪聲、高分辨率和高精度的優(yōu)點。對車輪轉(zhuǎn)速的測量實際上是對轉(zhuǎn)子旋轉(zhuǎn)引起的周期脈沖信號的頻率進(jìn)行測量。m1由測量準(zhǔn)確度確定。級時，這時測量準(zhǔn)確度主要由量化±1誤差來確定。樣周期將大大延長，并且判斷m1也要延長采樣周期，不適合實時測量。收發(fā)檢測系統(tǒng)，可以檢測電機(jī)的轉(zhuǎn)速。

　　

【正文】 m == t0_max) { int0_flag = 2。 TR0 = 0。 EA = 0。 } } include code tab[20]={0x3f,0x06,0x5b,0x4f,0x66,0x6d,0x7d,0x07,0x7f,0x6f, 0xbf,0x86,0xdb,0xcf,0xe6,0xed,0xfd,0x87,0xff,0xef}。 code btab[4]={0xfe,0xfd,0xfb,0xf7}。 第 42 頁 共 51 頁 unsigned char buf[4]={0,0,0,0}。 void bcd(int n) { buf[3]=(n/1000)%10。 buf[2]=(n/100)%10。 buf[1]=(n/10)%10。 buf[0]=n%10。 } void panshu(float m) //判斷數(shù)的范圍 { if(m=1000) { m = (int)m%10000。 bcd(m)。 } else if(m=100 amp。amp。 m1000) { m = m*10。 bcd(m)。 buf[1] = buf[1]+10。 } else if(m=10 amp。amp。 m100) { m = m*100。 bcd(m)。 buf[2] = buf[2]+10。 } else if(m=1 amp。amp。 m10) { 第 43 頁 共 51 頁 m = m*1000。 bcd(m)。 buf[3] = buf[3]+10。 } else if(m=0 amp。amp。 m1) { m = m*1000。 bcd(m)。 buf[3] = 10。 } } void delay(void) { unsigned int i。 for(i=0。i125。i++)。 } void display(float num) { unsigned int i。 panshu(num)。 for(i=0。i4。i++) { P2 |= 0x0f。 P0 = tab[buf[i]]。 P2 amp。= btab[i]。 delay()。 } } 第 44 頁 共 51 頁 外文原文 Microcontroller A microcontroller （ or MCU） is a puteronachip. It is a type of microprocessor emphasizing selfsufficiency and costeffectiveness, in contrast to a generalpurpose microprocessor （ the kind used in a PC） . The majority of puter 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 puter. They may control electric motors, relays or voltages, and read switches,variable resistors or other electronic , the only I/O device readable by a human is a single lightemitting diode,and severe cost or power constraints can even eliminate that. In contrast to generalpurpose CPUs, microcontrollers do not have an address bus or a data bus, because they integrate all the RAM and nonvolatile 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 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, monly with the following features: central processing unit ranging from small and simple 4bit processors to 第 45 頁 共 51 頁 sophisticated 32 or 64bit processors input/output interfaces such as serial ports （ UARTs） other serial munications interfaces like I178。C, 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 analogtodigital 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 timetomarket 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 among these are the 8051,Z80 and ARM derivatives.[citation needed] A microcontroller （ also MCU or 181。C） is a functional puter systemonachip. 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 第 46 頁 共 51 頁 additional elements such as readwrite memory for data storage, readonly 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 pared to microprocessors, but this is adequate for typical 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