外文文獻(xiàn)翻譯--超聲測距系統(tǒng)設(shè)計(jì)

1、<p>　　Ultrasonic ranging system design</p><p>　　Publication title: Sensor Review. Bradford: 1993.Vol.</p><p>　　ABSTRACT: Ultrasonic ranging technology has wide using worth in many fields, s

2、uch as the industrial locale, vehicle navigation and sonar engineering. Now it has been used in level measurement, self-guided autonomous vehicles, fieldwork robots automotive navigation, air and underwater target detect

3、ion, identification, location and so on. So there is an important practicing meaning to learn the ranging theory and ways deeply. To improve the precision of the ultrasonic ranging system in hand, satis</p><p&

4、gt;　　Keywords: Ultrasound, Ranging System, Single Chip Processor</p><p>　　1. Introductive</p><p>　　With the development of science and technology, the improvement of people’s standard of living,

5、 speeding up the development and construction of the city. Urban drainage system have greatly developed their situation is construction improving. However, due to historical reasons many unpredictable factors in the synt

6、hesis of her time, the city drainage system. In particular drainage system often lags behind urban construction. Therefore, there are often good building excavation has been building fa</p><p>　　2. A princip

7、le of ultrasonic distance measurement</p><p>　　The application of AT89C51:</p><p>　　SCM is a major piece of computer components are integrated into the chip micro-computer. It is a multi-interfa

8、ce and counting on the micro-controller integration, and intelligence products are widely used in industrial automation. and MCS-51 microcontroller is a typical and representative.</p><p>　　Microcontrollers

9、are used in a multitude of commercial applications such as modems, motor-control systems, air conditioner control systems, automotive engine and among others. The high processing speed and enhanced peripheral set of thes

10、e microcontrollers make them suitable for such high-speed event-based applications. However, these critical application domains also require that these microcontrollers are highly reliable. The high reliability and low m

11、arket risks can be ensured by a robust test</p><p>　　1.1 Features</p><p>　　* Compatible with MCS-51 Products</p><p>　　* 2Kbytes of Reprogrammable Flash Memory</p><p>　　

12、Endurance: 1,000Write/Erase Cycles</p><p>　　* 2.7V to 6V Operating Range</p><p>　　* Fully Static operation: 0Hz to 24MHz</p><p>　　* Two-level program memory lock</p><p>

13、;　　* 128x8-bit internal RAM</p><p>　　* 15programmable I/O lines</p><p>　　* Two 16-bit timer/counters</p><p>　　* Six interrupt sources</p><p>　　*Programmable serial UART

14、 channel</p><p>　　* Direct LED drive output</p><p>　　* On-chip analog comparator</p><p>　　* Low power idle and power down modes</p><p>　　1.2 Description</p><

15、p>　　The AT89C2051 is a low-voltage, high-performance CMOS 8-bit microcomputer with 2Kbytes of flash programmable and erasable read only memory (PEROM). The device is manufactured using Atmel’s high density nonvolatile

16、 memory technology and is compatible with the industry standard MCS-51 instruction set and pinout. By combining a versatile 8-bit CPU with flash on a monolithic chip, the Atmel AT89C2051 is a powerful microcomputer which

17、 provides a highly flexible and cost effective solution to many emb</p><p>　　The AT89C2051 provides the following standard features: 2Kbytes of flash, 128bytes of RAM, 15 I/O lines, two 16-bit timer/counters

18、, a five vector two-level interrupt architecture, a full duplex serial port, a precision analog comparator, on-chip oscillator and clock circuitry. In addition, the AT89C2051 is designed with static logic for operation d

19、own to zero frequency and supports two software selectable power saving modes. The idle mode stops the CPU while allowing the RAM, timer/counters, ser</p><p>　　1.3 Pin Configuration</p><p>　　1.4

20、 Pin Description</p><p>　　VCC Supply voltage.</p><p>　　GND Ground.</p><p><b>　　Prot 1</b></p><p>　　Prot 1 is an 8-bit bidirectional I/O port. Port pins

21、P1.2 to P1.7 provide internal pullups. P1.0 and P1.1 require external pullups. P1.0 and P1.1 also serve as the positive input (AIN0) and the negative input (AIN1), respectively, of the on-chip precision analog comparator

22、. The port 1 output buffers can sink 20mA and can drive LED displays directly. When 1s are written to port 1 pins, they can be used as inputs. When pins P1.2 to P1.7 are used as input and are externally pulled low, they

23、 will s</p><p><b>　　Port 3</b></p><p>　　Port 3 pins P3.0 to P3.5, P3.7 are seven bidirectional I/O pins with internal pullups. P3.6 is hard-wired as an input to the output of the on-

24、chip comparator and is not accessible as a general purpose I/O pin. The port 3 output buffers can sink 20mA. When 1s are written to port 3 pins they are pulled high by the internal pullups and can be used as inputs. As i

25、nputs, port 3 pins that are externally being pulled low will source current (IIL) because of the pullups.</p><p>　　Port 3 also serves the functions of various special features of the AT89C2051 as listed belo

26、w.</p><p>　　1.5 Programming the Flash</p><p>　　The AT89C2051 is shipped with the 2 Kbytes of on-chip PEROM code memory array in the erased state (i.e., contents=FFH) and ready to be programmed.

27、The code memory array is programmed one byte at a time. Once the array is programmed, to re-program any non-blank byte, the entire memory array needs to be erased electrically.</p><p>　　Internal address coun

28、ter: the AT89C2051 contains an internal PEROM address counter which is always reset to 000H on the rising edge of RST and is advanced applying a positive going pulse to pin XTAL1.</p><p>　　Programming algori

29、thm: to program the AT89C2051, the following sequence is recommended.</p><p>　　1. power-up sequence:</p><p>　　Apply power between VCC and GND pins Set RST and XTAL1 to GND</p><p>　　

30、With all other pins floating , wait for greater than 10 milliseconds</p><p>　　2. Set pin RST to ‘H’ set pin P3.2 to ‘H’</p><p>　　3. Apply the appropriate combination of ‘H’ or ‘L’ logic to pins

31、P3.3, P3.4, P3.5, P3.7 to select one of the programming operations shown in the PEROM programming modes table.</p><p>　　To program and Verify the Array:</p><p>　　4. Apply data for code byte at l

32、ocation 000H to P1.0 to P1.7.5.Raise RST to 12V to enable programming.</p><p>　　5. Pulse P3.2 once to program a byte in the PEROM array or the lock bits. The byte-write cycle is self-timed and typically take

33、s 1.2ms.</p><p>　　6. To verify the programmed data, lower RST from 12V to logic ‘H’ level and set pins P3.3 to P3.7 to the appropriate levels. Output data can be read at the port P1 pins.</p><p>

34、;　　7. To program a byte at the next address location, pulse XTAL1 pin once to advance the internal address counter. Apply new data to the port P1 pins.</p><p>　　8. Repeat steps 5 through 8, changing data and

35、 advancing the address counter for the entire 2 Kbytes array or until the end of the object file is reached.</p><p>　　9. Power-off sequence: set XTAL1 to ‘L’ set RST to ‘L’</p><p>　　Float all ot

36、her I/O pins Turn VCC power off</p><p>　　2.1 The principle of piezoelectric ultrasonic generator</p><p>　　Piezoelectric ultrasonic generator is the use of piezoelectric crystal resonators to wor

37、k. Ultrasonic generator, the internal structure as shown, it has two piezoelectric chip and a resonance plate. When it’s two plus pulse signal, the frequency equal to the intrinsic piezoelectric oscillation frequency ch

38、ip, the chip will happen piezoelectric resonance, and promote the development of plate vibration resonance, ultrasound is generated. Conversely, it will be for vibration suppression of piezoel</p><p>　　The t

39、raditional way to determine the moment of the echo’s arrival is based on thresholding the received signal with a fixed reference. The threshold is chosen well above the noise level, whereas the moment of arrival of an ec

40、ho is defined as the first moment the echo signal surpasses that threshold. The intensity of an echo reflecting from an object strongly depends on the object’s nature, size and distance from the sensor. Further, the time

41、 interval from the echo’s starting point to the moment </p><p>　　2.2 The principle of ultrasonic distance measurement</p><p>　　Ultrasonic transmitter in a direction to launch ultrasound, in the

42、moment to launch the beginning of time at the same time, the spread of ultrasound in the air, obstacles on his way to return immediately, the ultrasonic reflected wave received by the receiver immediately stop the clock.

43、 Ultrasound in the air as the propagation velocity of 340m/s, according to the timer records the time t, we can calculate the distance between the launch distance barrier(s), that is: s=340t / 2</p><p>　　3.

44、Ultrasonic Ranging System for the Second Circuit Design</p><p>　　System is characterized by single-chip microcomputer to control the use of ultrasonic transmitter and ultrasonic receiver since the launch fro

45、m time to time, single-chip selection of 875, economic-to-use, and the chip has 4K of ROM, to facilitate programming. </p><p>　　3.1 40 kHz ultrasonic pulse generated with the launch</p><p>　　Ran

46、ging system using the ultrasonic sensor of piezoelectric ceramic sensors UCM40, its operating voltage of the pulse signal is 40kHz, which by the single-chip implementation of the following procedures to generate.</p&

47、gt;<p>　　puzel: mov 14h, # 12h; ultrasonic firing continued 200ms</p><p>　　Here: cpl p1.0; output 40kHz square wave</p><p><b>　　nop;</b></p><p>

48、<b>　　nop;</b></p><p><b>　　nop;</b></p><p>　　djnz 14h, here;</p><p><b>　　ret</b></p><p>　　Ranging in front of single-chip termina

49、tion circuit P1.0 input port, single chip implementation of the above procedure, the P1.0 port in a 40kHz pulse output signal, after amplification transistor T, the drive to launch the first ultrasonic UCM40T, issued 40k

50、Hz ultrasonic pulse, and the continued launch of 200ms. Ranging the right and the left side of the circuit, respectively, then input port P1.1 and P1.2, the working principle and circuit in front of the same location.&

51、lt;/p><p>　　3.2 Reception and processing of ultrasonic</p><p>　　Used to receive the first launch of the first pair UCM40R, the ultrasonic pulse modulation signal into an alternating voltage, the op

52、-amp amplification IC1A and after polarization IC1B to IC2. IC2 is locked loop with audio decoder chip LM567, internal voltage-controlled oscillator center frequency of f0=1/1.1R8C3, capacitor C4 determine their target b

53、andwidth. R8-conditioning in the launch of the high jump 8 feet into a low-level, as interrupt request signals to the single-chip processing.</p><p>　　Ranging in front of single-chip termination circuit outp

54、ut port INT0 interrupt the highest priority, right or left location of the output circuit with output gate IC3A access INT1 port single-chip, while single-chip P1.3 and P1.4 received input IC3A, interrupted by the proces

55、s to identify the source of inquiry to deal with, interrupt priority level for the first left right after. Part of the source code is as follows: </p><p>　　Receivel: push psw</p><p><b>　　p

56、ush acc</b></p><p>　　clr ex1; related external interrupt 1</p><p>　　jnb p1.1, right; P1.1 pin to 0, ranging from right to interrupt service routine circuit</p><p>　　jnb p1.2,

57、 left; P1.2 pin to 0, to the left ranging circuit interrupt service routine</p><p>　　return: SETB EX1; open external interrupt 1</p><p><b>　　pop acc</b></p><p><b&g

58、t;　　pop psw</b></p><p><b>　　reti </b></p><p>　　right: …; right location entrance circuit interrupt service routine</p><p>　　Ajmp Return</p><p>　

59、　left: …; left ranging entrance circuit interrupt service routine</p><p>　　Ajmp Return</p><p>　　3.3 The calculation of ultrasonic propagation time</p><p>　　When you start firi

60、ng at the same time start the single-chip circuitry within the timer T0, the use of timer counting function records the time and the launch of ultrasonic reflected wave received time. When you receive the ultrasonic refl

61、ected wave, the receiver circuit output a negative jump in the end of INT0 or INT1 interrupt request generates a signal, single-chip microcomputer in response to external interrupt request, the implementation of the exte

62、rnal interrupt service subroutine, read t</p><p>　　RECEIVE0: PUSH PSW</p><p>　　PUSH ACC</p><p>　　CLR EX0; related external interrupt 0</p><p>　　MOV R7, TH0; rea

63、d the time value</p><p>　　MOV R6, TL0</p><p><b>　　CLR C</b></p><p>　　MOV A, R6</p><p>　　SUBB A, #0BBH; calculate the time difference</p><

64、p>　　MOV 31H, A; storage results</p><p>　　MOV A, R7</p><p>　　SUBB A, # 3CH</p><p>　　MOV 30H, A</p><p>　　SETB EX0; open external interrupt 0\</p><

65、p><b>　　POP ACC</b></p><p><b>　　POP PSW</b></p><p><b>　　RETI</b></p><p>　　For a flat target, a distance measurement consists of two phases:

66、 a coarse measurement and a fine measurement:</p><p>　　Step 1: Transmission of one pulse train to produce a simple ultrasonic wave.</p><p>　　Step 2: Changing the gain of both echo amplifiers acc

67、ording to equation, until the echo is detected.</p><p>　　Step 3: Detection of the amplitudes and zero-crossing times of both echoes.</p><p>　　Step 4: Setting the gains of both echo amplifiers to

68、 normalize the output at, say 3 volts. Setting the period of the next pulses according to the: period of echoes. Setting the time window according to the data of step 2.</p><p>　　Step 5: Sending two pulse tr

69、ains to produce an interfered wave. Testing the zero-crossing times and amplitudes of the echoes. If phase inversion occurs in the echo, determine to otherwise calculate to by interpolation using the amplitudes near the

70、trough. Derive t sub m1 and t sub m2.</p><p>　　Step 6: Calculation of the distance y using equation.</p><p>　　4、The ultrasonic ranging system software design</p><p>　　Software is di

71、vided into two parts, the main program and interrupt service routine. Completion of the work of the main program is initialized, each sequence of ultrasonic transmitting and receiving control.</p><p>　　Inter

72、rupt service routines from time to time to complete three of the rotation direction of ultrasonic launch, the main external interrupt service subroutine to read the value of completion time, distance calculation, the res

73、ults of the output and so on.</p><p>　　5、Conclusions</p><p>　　Required measuring range of 30cm-200cm objects inside the plane to do a number of measurements found that the maximum error is 0.5cm

74、, and good reproducibility. Single-chip design can be seen on the ultrasonic ranging system has a hardware structure is simple, reliable, small features such as measurement error. Therefore, it can be used not only for m

75、obile robot can be used in other detection system.</p><p>　　Thoughts: As for why the receiver do not have the transistor amplifier circuit, because the magnification well, integrated amplifier, but also with

76、 automatic gain control level, magnification to 76dB, the center frequency is 38k to 40k, is exactly resonant ultrasonic sensors frequency.</p><p>　　6、Parking sensor</p><p>　　6.1 Parking sensor&

77、#160;introduction</p><p>　　Reversing radar, full name is "reversing the anti-collision radar, also known as" parking assist device,  car parking or reversing the safet

78、y of assistive devices,  ultrasonic sensors(commonly known as probes),  controls and displays (or buzzer)and other components. To inform the driver around the obstacle

79、60;to the sound or a more intuitive display to lift the driver parking,  reversing and start the vehicle around to visit the distress caused

80、 by,  and to help the driver to remove the vision dead </p><p>　　6.2 Reversing radar detection principle</p><p>　　Reversing radar, according to&

81、#160;high-speed flight of the bats in the night,  not collided with any obstacle principles of design and development.  Probe mounted on the rear bumper, a

82、ccording to different price and brand, the probe only ranging from two, three, four, six, eight, respectively,  pipe around.  The probe radiation,  45-degr

83、ee angle up and down about the search target.  The greatest advantage is to explore lower than the bumper of the driver from the rear window is diffic

84、ult to see obst</p><p>　　Display parking sensor installed in the rear view mirror,  it constantly remind drivers to car distance behind the object 

85、distance to the dangerous distance,  the buzzer starts singing, allow the driver to stop.  When the gear lever linked into reverse gear, reversi

86、ng radar, auto-start the work,  the working range of 0.3 to 2.0 meters, so stop when the driver was very practical.  Reversing radar is equivalent to

87、 an ultrasound probe for ultrasonic probe can be divided into two categories:  Firs</p><p>　　6.3 Reversing radar functionality and performance</p><p>　　Pa

88、rking sensor can be divided into the LCD distance display, audible alarm,  and azimuth directions, voice prompts,  automatic probe detection function

89、is complete, reversing radar distance,  audible alarm,  position-indicating function.  A good performance reversing radar,  its main properties include: &#

90、160;(1) sensitivity,  whether the response fast enough when there is an obstacle.  (2) the existence of blind spots.  (3) detection distance range.</p>&

91、lt;p>　　6.4  Each part of the role</p><p>　　Reversing radar has the following effects:  (1) ultrasonic sensor: used to launch and receive ultrasonic signals,&

92、#160;ultrasonic sensors can measure distance.  (2)  host:  after the launch of the sine wave pulse to the ultrasonic sensors, and process the rec

93、eived signal, to calculate the distance value, the data and monitor communication.  (3) display or abuzzer: the receiving host from the data,  and dis

94、play the distance value and provide different levels according to the distance from the alarm s</p><p>　　6.5 Cautions</p><p>　　1, the

95、 installation height:  general ground: car before the installation of 45 ~ 55: 50 ~ 65cmcar after installation.  2,  regular cleaning of the 

96、;probe to prevent the fill.  3,  do not use the hard stuff the probe surface cover will produce false positives or ranging allowed to p

97、robe surface coverage,  such as mud.  4, winter to avoid freezing.  5, 6 / 8 probe reversing radar before and after the probe is not free to 

98、;swap may cause the Chang Ming false positive problem.  6, note that the prob</p><p><b>　　超聲測距系統(tǒng)設(shè)計(jì)</b></p><p>　　原文出處：傳感器文摘 布拉福德：1993年</p&

99、gt;<p>　　超聲測距技術(shù)在工業(yè)現(xiàn)場、車輛導(dǎo)航、水聲工程等領(lǐng)域具有廣泛的應(yīng)用價(jià)值，目前已應(yīng)用于物位測量、機(jī)器人自動(dòng)導(dǎo)航以及空氣中與水下的目標(biāo)探測、識(shí)別、定位等場合。因此，深入研究超聲的測距理論和方法具有重要的實(shí)踐意義。為了進(jìn)一步提高測距的精確度，滿足工程人員對測量精度、測距量程和測距儀使用的要求，本文研制了一套基于單片機(jī)的便攜式超聲測距系統(tǒng)。</p><p>　　關(guān)鍵詞：超聲波、測距儀、單片機(jī)&

100、lt;/p><p><b>　　1、前言</b></p><p>　　隨著科技的發(fā)展，人們生活水平的提高，城市發(fā)展建設(shè)加快，城市給排水系統(tǒng)也有較大發(fā)展，其狀況不斷改善。但是，由于歷史原因合成時(shí)間的許多不可預(yù)見因素，城市給排水系統(tǒng)，特別是排水系統(tǒng)往往落后于城市建設(shè)。因此，經(jīng)常出現(xiàn)開挖已經(jīng)建設(shè)好的建筑設(shè)施來改造排水系統(tǒng)的現(xiàn)象。城市污水給人們帶來了困擾，因此箱涵的排污疏通對大城

101、市給排水系統(tǒng)污水處理，人們生活舒適顯得非常重要。而設(shè)計(jì)研制箱涵排水疏通移動(dòng)機(jī)器人的自動(dòng)控制系統(tǒng)，保證機(jī)器人在箱涵中自由排污疏通，是箱涵排污疏通機(jī)器人的設(shè)計(jì)研制的核心部分?？刂葡到y(tǒng)核心部分就是超聲波測距儀的研制。因此，設(shè)計(jì)好的超聲波測距儀就顯得非常重要了。</p><p><b>　　2、超聲波測距原理</b></p><p>　　AT89C51應(yīng)用：</p>

102、;<p>　　單片機(jī)是把主要計(jì)算機(jī)功能部件都集成在一塊芯片上的微型計(jì)算機(jī)。它是一種集計(jì)數(shù)和多中接口于一體的微控制器，被廣泛應(yīng)用在智能產(chǎn)品和工業(yè)自動(dòng)化上，而51單片機(jī)是個(gè)單片機(jī)中最為典型和最有代表性的一種。</p><p>　　單片機(jī)廣泛應(yīng)用于商業(yè)：諸如調(diào)制解調(diào)器，電動(dòng)機(jī)控制系統(tǒng)，空調(diào)控制系統(tǒng)，汽車發(fā)動(dòng)機(jī)和其他一些領(lǐng)域。這些單片機(jī)的高速處理速度和增強(qiáng)型外圍設(shè)備集合使得它們適合于這種高速事件應(yīng)用場合。然

103、而，這些關(guān)鍵應(yīng)用領(lǐng)域也要求這些單片機(jī)高度可靠。強(qiáng)大的測試環(huán)境和用于驗(yàn)證這些無論在元部件層次還是系統(tǒng)級別的單片機(jī)的合適的工具環(huán)境保證了高可靠性和低市場風(fēng)險(xiǎn)。Intel 平臺(tái)工程部門開發(fā)了一種面向?qū)ο蟮挠糜隍?yàn)證它的AT89C51 汽車單片機(jī)多線性測試環(huán)境。這種環(huán)境的目標(biāo)不僅是為AT89C51 汽車單片機(jī)提供一種強(qiáng)大測試環(huán)境，而且開發(fā)一種能夠容易擴(kuò)展并重復(fù)用來驗(yàn)證其他幾種將來的單片機(jī)。開發(fā)的這種環(huán)境連接了AT89C51。</p>

104、<p><b>　　1.1 特點(diǎn)</b></p><p>　　* 兼容MCS-51 產(chǎn)品</p><p>　　* 2字節(jié)的可再編程閃存</p><p><b>　　耐力擦寫/擦除周期</b></p><p>　　* 2.7V 至 6V 工作范圍</p><p>　

105、　* 全靜態(tài)操作存儲(chǔ)器鎖定</p><p>　　* 兩級程序存儲(chǔ)器鎖定</p><p>　　* 128 x 8位內(nèi)部RAM</p><p>　　* 15個(gè)可編程I/O線</p><p>　　* 2個(gè)16位定時(shí)器/計(jì)數(shù)器</p><p><b>　　* 六個(gè)中斷源</b></p>&l

106、t;p>　　* 可編程串行UART通道</p><p>　　* 直接LED驅(qū)動(dòng)輸出</p><p><b>　　* 片上模擬比較器</b></p><p>　　* 低功耗空閑和掉電模式</p><p><b>　　1.2 說明</b></p><p>　　該AT89C2

107、051是一個(gè)低電壓，高性能CMOS 8位2Kbytes 的flash可編程，可擦除只讀存儲(chǔ)器（PEROM）設(shè)備是制造采用Atmel的高密度非易失性內(nèi)存技術(shù)，并與兼容的工商業(yè)污水附加費(fèi)微機(jī)工業(yè)標(biāo)準(zhǔn)MCS-51指令集，并通過結(jié)合在一個(gè)通用的單芯片閃存的8位CPU引腳，Atmel的AT89C2051是一種功能強(qiáng)大的微機(jī)提供了高度靈活和成本效益的解決方案，許多嵌入式控制應(yīng)用。</p><p>　　該AT89C2051提供

108、以下標(biāo)準(zhǔn)功能2字節(jié)的閃存，128字節(jié)RAM，15 I/O線，兩個(gè)16位定時(shí)器/計(jì)數(shù)器，一個(gè)五向量2級中斷結(jié)構(gòu)，一個(gè)全雙工串行口，一個(gè)精密模擬比較器，片上振蕩器和時(shí)鐘電路此外，該AT89C2051的設(shè)計(jì)與操作頻率下降到零靜態(tài)邏輯，支持兩種軟件可選的節(jié)電模式空閑模式時(shí)CPU停止工作，同時(shí)允許RAM，定時(shí)/計(jì)數(shù)器，串行口和中斷系統(tǒng)繼續(xù)工作暫停模式保存RAM的內(nèi)容，但凍結(jié)，直到下一個(gè)硬件復(fù)位振蕩器禁用所有其他芯片功能。</p>&

109、lt;p><b>　　1.3 引腳配置</b></p><p><b>　　1.4 引腳說明</b></p><p>　　VCC 電源電壓</p><p><b>　　GND 接地</b></p><p><b>　　端口 1</b><

110、/p><p>　　端口 1是一個(gè)8位雙向 I/O 端口引腳P1.2 至P1.7，提供P1.1和P1.0內(nèi)部上拉需要P1和P1.1外部上拉也可作為正輸入（AIN0）和服輸入（AIN1），分別對片內(nèi)精密模擬比較器的端口1 輸出緩沖器可以吸收20mA的電流，并且可以直接驅(qū)動(dòng)LED時(shí)1秒寫入端口1引腳，他們可以作為輸入引腳P1.2時(shí)至P1.7作為輸入，并從外部拉低，將輸出電流（IIL）由于內(nèi)部上拉在端口1也接收片內(nèi)flash