分布式溫度傳感器[中文4137字] 【中英文WORD】,中文4137字,中英文WORD,分布式溫度傳感器[中文4137字],【中英文WORD】,分布式,溫度傳感器,中文,4137,中英文,WORD 外文文獻(xiàn)資料 Distributed Temperature Sensor 1.Sensor introduction 1.1 Temperature sensor background In the human living environment, temperature playing an extremely important role。No matter where you live, engaged in any work, ever-present dealt with temperature under. Since the 18th century, industry since the industrial revolution to whether can master send exhibition has the absolute temperature touch. In metallurgy, steel, petrochemical, cement, glass, medicine industry and so on, can say almost eighty percent of industrial departments have to consider the factors with temperature. Temperature for industrial so important, thus promoting the development of the temperature sensor. 1.2 Temperature sensor development Major general through three sensor development phase: analog integrated temperature sensor. The sensor is taken with silicon semiconductor integrated workmanship, therefore also called silicon sensor or monolithic integrated temperature sensor. Such sensing instruments have single function (only measuring temperature), temperature measurement error is smaller, price low, fast response, the transmission distance, small volume, micro-consumption electronic etc, suitable for long distance measurement temperature, temperature control, do not need to undertake nonlinear calibration, peripheral circuit is simple. It is currently the most common application at home and abroad, an integrated sensor。Typical products have AD590 AD592, TMP17, LM135, etc.jAnalog integrated temperature controller. Analog integrated temperature controller mainly include temperature control switch, programmable temperature controller, a typical product have LM56, AD22105 and MAX6509. Some increase strength type integrated temperature controller (for example TC652/653) also contains the A/D converter and cure good sequence, this process with the intelligent temperature sensor some similarities. But it is not its system, work by micro processing device control, this is the main difference between. Intelligent temperature sensor. intelligent temperature sensor (also called digital temperature degrees sensor) is in the mid 1990s launch. It is microelectronics technology, computer technology and the dynamic testing technology (ATE) crystallization. Intelligent temperature sensor internal contain temperature sensor, A/D converter, signal processor, memory (or registers) and interface circuit. Some products still take multiplexer, central control system device (CPU), random access memory (RAM) and read only memory (ROM). Intelligent temperature sensor is characteristic of temperature data and relevant can output the temperature control of the quantity, adaptation various micro controller (MCU); 1.3 Single point and more temperature sensor The development trend of the temperature sensor. In the 21st century, the temperature sensor is headed in high precision, multi-function, bus, standardization, high reliability and safety, development of virtual sensor and network sensor, research monolithic temperature measuring system and other high-tech direction develop rapidly. Sensors in the application temperature controlling system. Current market exists mainly single point and more two temperature measurement. For single point temperature foundment instrument, mainly adopts the traditional analog integrated temperature sensor, which heat resistance, thermocouple sensors measuring accuracy, high measurement range, and got the general application. This product is temperature measuring range ℃ ~ 200 mostly between 800 ℃, resolution 12th, and least distinguishable temperature in 0.001 ~ 0.01 between. Cabin LED display module, shows ranging from 4 to 16. Some instruments also has memory function, can store several hundred to a few thousand sets of data. This instrument can be very good meet a single user single-point measurement needs. More temperature measurement, relative and single point measurement precision has certain gap, although realized the multi-channel temperature measurement and control, but the price is expensive. In view of the present market situation, proposed this topic can satisfy requirements, scalable and cost-effective single-chip multi-channel temperature measuring system. Through the first temperature sensor DS18B20 acquisition, and then through the C51 SCM processing and displayed on the digital tube, can be collected indoor or a greenhouse around in different locations of the temperature, with four digital tube to display. The first digital pipe display acquisition is which way, which channel. Three digital pipe display after the acquisition channel by temperature, accurate to 0.1 degrees. 2. The system realized and related technologies 2.1.The system is realized By the whole control system for core AT89C51, using four ways of temperature sensor DS18B20 in production site for distribution area of four different temperature measurement result with the chip checking, collation store and display, and through the button control, temperature will process after the LED digital display to come out, and the software assurance system anti-interference capacity。four DS1820 connected to MCU respectively, this scheme four IO mouth occupy MCU four IO though, but the microcontroller IO mouth under the condition of mouth not shortage by this scheme greatly simplify programming difficulty, shorten the design cycle, also can guarantee the stability of the system. A multipoint connection as shown“1-1” DS1820 DS1820 DS1820 DS1820 AT89C51 MCU P1.0 P1.1 P1.2 P1.3 P3.4 Display element Button control unit 1-1 multipoint connection 2.2 .AT89C51 Chip introduction AT89C51 is a 4K bytes FLASH Memory (Erasable Programmable and FPEROM - FLASH for the campaigns with) low voltage, high-performance CMOS eight microprocessors, commonly known as the microcontroller. AT89C2051 is a 2K bytes with flash memory can be erased programmable read-only memory , SCM can erase read-only memory can be repeated erased 1000 times. This device adopts ATMEL high-density non-volatile memory manufacturing technology manufacturing, and industrial standard MCS - 51 instruction set and output tube compatible. Due to the multifunctional 8 bits CPU and will be flashing on single chip combination of memory, ATMEL AT89C51 is a kind of high efficient micro controller, AT89C2051 is a streamlined version. AT89C 51microcontroller as many embedded control system .Arrange appearance and pin as shown in figure "1-2" shown 1-2 AT89C51 pins figure Major features: · and MCS - 51 compatible · 4K bytes programmable FLASH memory · life: 1000 write/wipe cycle · data retention time: 10 years · the static job: 0Hz - 24MHz · level 3 program memory lock · 128 x 8 bits internal RAM · 32 programmable I/O lines · two 16 timer · 5 interrupt source · programmable serial channels · low power consumption of idle and power lost mode · piece inside oscillator and clock circuit Tube feet explains: VCC: power supply voltage. GND: grounded. P0 Mouth: P0 mouth a eight leak level two-way I/O mouth open, every foot can absorb 8TTL gate current. When the pipe mouth P0 feet first write 1, defined as high resistance input. P0 can be used for external program data storage, it can be defined as the eighth data/address. In FIASH programming, P0 mouth as the source-code input port, when FIASH check, the source-code P0 output, when P0 external must be pulled. P1 mouth: mouth is an internal P1 provide pull-up resistors 8-bit two-way I/O mouth, P1 mouth buffer can receive 4TTL gate current output. P1 mouth tube feet, was then write 1 for high, pull up inside can be used as input, P1 mouth be external pull down for low electricity at ordinary times, will output current, this is due to internal pull up sake. In FLASH programming and calibration, P1 mouth as eighth address to receive. P2 mouth: for an internal P2 mouth on the 8-bit pull-up resistors two-way I/O port, P2 mouth to receive, the output buffer 4 TTL gate current, when P2 mouth is written "1", its tube feet are internal pull-up resistors, and push as input. And so as the input, P2 mouth feet are external down tube, will output current. This is due to internal pull up sake. P2 mouth when used external program memory or 16 address external data memory access, P2 mouth high output address eight. In a given address "1", it using internal and external 8 address advantage, when for reading and writing data memory, P2 when the special function registers mouth output of content. P2 mouth in FLASH programming and the calibration eight address when receiving high signal and control signals. P3 mouth: P3 mouth pipe is 8 feet with internal pull-up resistors two-way I/O port, may receive four TTL gate current out put. When P3 mouth writing "1", they are internal and high level, and used as input. As input, due to external drop-down for low level, P3 mouth will output current (ILL) this is due to pull up's sake. RST: reset input. When oscillator reset device to keep RST feet high level two machine cycle time. ALE/PROG: when access external storage, address latch allows the output level of the position for latch address byte. During the FLASH programming, this pin for input programming pulse. In peacetime, the ALE with a constant frequency cycle output is the pulse signal, the frequencies of the 1/6 oscillator frequency. So it can be used against external output pulse or used for timing purpose. However it is: whenever used for external data storage, will skip a ALE pulse. If you want to ban the ALE output can be in SFR8EH address for 0. At this time, only by performing the ALE MOVX, MOVC instruction is ALE to take effect. In addition, the pins were slightly up. If microprocessor in external execution ALE, buy a ban is invalid. / PSEN: external program memory choice of communication number. By external program memory in during the instruction fetch, each machine cycle twice /PSEN effective. But on a visit to external data storage, the two effective/PSEN signals will not appear. / EA/VPP: when/EA keep low levels in this period, the external program memory (0000H - FFFFH), whether have internal program memory. Note encryption method 1, / EA will RESET for internal focus; When/EA end keep high electricity at ordinary times, internal program memory here. During the FLASH programming, this pin is also used VPP 12V programming power (on). XTAL1: the inverting oscillator amplifier input and input to the internal clock operating circuit. XTAL2: from reverse oscillator output. 2.3.DS18B20 Chip introduction DALLAS latest digital temperature sensor DS18B20 profile new "1-wire devices" smaller, wider and voltage applied to the DALLAS semiconductor company more economic DS1820 digital temperature sensor is the world the first piece of support "1-wire bus" interface temperature sensor. 1-wire bus unique and economic characteristics, the user can easily form sensor network for measuring system, the construction of a new concept introduction. DS18B20 "1-wire bus" with DS1820 digital temperature sensor DS18B20 also support "as 1-wire bus" interface, measuring temperature range for - 55 ° C ~ + 125 ° C, in - 10 ~ + 85 ° C range, precision ° C for + 0.5. Scene in "1-wire bus temperature directly the digital mode," can greatly improve the system of anti-jamming. Suitable for the scene in the bad environment temperature measurement, such as: environment control, equipment or process control, temperature measurement of consumer electronics, etc. And the previous generation product is different, the new product support 3V ~ 5.5 V voltage range, make the system design more flexibly and conveniently. But a new generation of products cheaper, smaller. DS18B20 can program sets 9 ~ 12 resolution, precision ° C for + 0.5. Optional smaller encapsulation way, more wide voltage range. Resolution setting, and users set alarm temperature EEPROM, stored in power lost and still save. DS18B20 performance is the best product of new generation! Performance to price also is very good! DS18B20 New performance: (1) data available supply, voltage range: 3.0 ~ 5.5 V; (2) temperature measuring range: - 55 ℃ ~ + 125 in - 10 ~ + 85 ℃ to + 0.5 ℃ when precision; (3) programmable resolution for the 9 ~ 12, the corresponding can distinguish respectively ℃, the temperature of 0.5 ℃ and 0.125 ℃, by 0.25 0.0625 ℃; (4) 12 resolution in most 750ms temperature into digital within; (5) negative pressure characteristics: power at the polarity, thermometers won't because when heating and burned, but can't work normally. DS18B20 Appearance and internal structure: DS18B20 internal structure consists mainly of four parts: 64-bit photolithography ROM, temperature sensors, nonvolatile temperature alarm triggers TH TL, configuration and registers. DS18B20 tube feet arrangement is “1-3”， internal structure is“1-4” 1-3 DS18B20 tube feet arrangement (1) DQ for digital signal input/output terminal; (2) GND for power; (3) VDD for external power supplies input (in parasitic power connection mode grounding). 1-4 internal structure 3. Debug simulation 3.1.Protues Proteus is Labeenter electronics company research UK EDA software. Proteus is not only the analog and digital circuit, d/a hybrid circuit design and simulation platform, but also is currently the world's most advanced, the most complete various types of micro controller system design and simulation platform. It really realized complete on computer schematic design, from circuit analysis and simulation and single-chip microcomputer and grade debugging and simulation, code system test and functional verification of the PCB formation to complete the design and development process of electronic. Proteus product series also contains a revolutionary VSM technology based on micro control, can the design with all peripheral electronic device simulation together. First start Proteus and Proteus components from the library selection need drawing diagram and set component, the corresponding element parameter values 3.2. Keilc Keil Vision 2 is about the 8051 series MCU Keil company of development tools can be used to compile C source code, assemblers source program, connection and relocation target files and libraries, gen built: documents, debugging purposes procedure, etc, it is a kind of integration of document management compile environment. It integrates document editing processing, compile connection, project management, window, tools cited and software copy true debugging and other functions, is pretty powerful development tool. In keil inside compile, the procedures required commissioning 3.3. alignment (1) detection TCP/IP. (2) duplicate the Proteus installation directory vdm51. Who folder keilc/C51 / DLL to bin directory. (3) modify the installation directory Keil tools. TDRV4 = BIN, add the DLL. VDM51. \ (4) in the schematic drawing Proteus, in "Debug menu, select" Use Remote Debug hand ". (5) in open in a project Keil, right-click Target1, choose for - Target 'Target 1'. In the open dialog box select "De - bug TAB, select and use VSM Proteus Emulator simulation (figure 6 shows), click" Ok "complete Debug Settings. 6 graph 6 such Keil Proteus and is connected, the simulation results can be in Proteus or Keil. This circuit system USES "1-wire bus" digital sensor DS18B20 to realize the collection of temperature, using seven segment digital tube data shows. Will program and simulation diagram realization circuit connected, simulation 第 15 頁(yè) 中文翻譯稿 分布式溫度傳感器 1傳感器簡(jiǎn)介 1.1溫度傳感器的背景 在人類生活環(huán)境中，溫度扮演著一個(gè)極其重要的角色。無(wú)論你住在哪里，從事什么工作，都會(huì)與溫度打交道。自18世紀(jì)工業(yè)時(shí)代以來(lái)，工業(yè)革命對(duì)能否控制，發(fā)送顯示溫度有著絕對(duì)的聯(lián)系。在冶金、鍛鋼、石化、水泥、醫(yī)學(xué)等產(chǎn)業(yè)中，可以這樣說(shuō)幾乎80%的工業(yè)部門(mén)不得不考慮溫度的因素。溫度對(duì)工業(yè)來(lái)說(shuō)如此重要，因此也推動(dòng)了溫度傳感器的發(fā)展。 1.2溫度傳感器的發(fā)展 傳感器主要大體經(jīng)過(guò)了三個(gè)發(fā)展階段：模擬集成溫度傳感器。該傳感器是采用硅半導(dǎo)體集成工藝制成，因此亦稱硅傳感器或單片集成溫度傳感器。此種傳感器具有功能單一(僅測(cè)量溫度)、 測(cè)溫誤差小、 價(jià)格低、 響應(yīng)速度快、 傳輸距離遠(yuǎn)、 體積小、功耗低，適合遠(yuǎn)距離測(cè)溫、控溫，不需要進(jìn)行非線性校準(zhǔn)，外圍電路 簡(jiǎn)單。它是目前在國(guó)內(nèi)外應(yīng)用最為普遍的一種集成傳感器，典型產(chǎn)品有 AD590、 AD592、TMP17、LM135 等；模擬集成溫度控制器。模擬集成溫度控制器主要包括溫度控制開(kāi)關(guān)、可編程溫度控制器，典型產(chǎn)品有 LM56、AD22105 和 MAX6509。某些增強(qiáng)型集成溫度控制器(例如 TC652/653)中還包含了 A/D 轉(zhuǎn)換器以及固化好的程序，這些工藝與智能溫度傳感器有某些相似之處。但它自成系統(tǒng)，工作時(shí)并不受微處理器的控制，這是智能溫度傳感器和非智能之間的主要區(qū)別；智能溫度傳感器(亦稱數(shù)字溫度傳感器)是20世紀(jì)90年代中期問(wèn)世的。它是微電子技術(shù)、計(jì)算機(jī)技術(shù)和自動(dòng)測(cè)試技術(shù)(ATE)的結(jié)晶。智能溫度傳感器內(nèi)部都包含溫度傳感器、A/D 轉(zhuǎn)換器、 信號(hào)處理器、存儲(chǔ)器(或寄存器)和接口電路。有的產(chǎn)品還帶多路選擇器、中央控制器(CPU)、隨機(jī)存取存儲(chǔ)器(RAM)和只讀存儲(chǔ)器(ROM)。智能溫度傳感器的特點(diǎn) 是能輸出溫度數(shù)據(jù)及相關(guān)的溫度控制量，適配各種微控制器(MCU)。 1.3單點(diǎn)與多點(diǎn)溫度傳感器 溫度傳感器的發(fā)展趨勢(shì)：進(jìn)21世紀(jì)后，溫度傳感器正朝著高精度、多功能、總線標(biāo)準(zhǔn)化、高可靠性及安全性、開(kāi)發(fā)虛擬傳感器和網(wǎng)絡(luò)傳感器、研制單片測(cè)溫系統(tǒng)等高科技的方向迅速發(fā)展。傳感器在溫度測(cè)控系統(tǒng)中的應(yīng)用：目前市場(chǎng)主要存在單點(diǎn)和多點(diǎn)兩種溫度測(cè)量?jī)x表。對(duì)于單點(diǎn)溫測(cè)儀表，主要采用傳統(tǒng)的模擬集成溫度傳感器，其中又以熱電阻、熱電偶等傳感器的測(cè)量精度 高，測(cè)量范圍大，而得到了普遍的應(yīng)用。此種產(chǎn)品測(cè)溫范圍大都在-200℃~800℃ 之間，分辨率 12 位，最小分辨溫度在 0.001~0.01 之間。自帶 LED液晶顯示模塊，顯示 4 位到 16 位不等。有的儀表還具有存儲(chǔ)功能，可存儲(chǔ)幾百到幾千組數(shù)據(jù)。該類儀表可很好的滿足單個(gè)用戶單點(diǎn)測(cè)量的需要。多點(diǎn)溫度測(cè)量?jī)x表，相對(duì)與單點(diǎn)的測(cè)量精度有一定的差距，雖然實(shí)現(xiàn)了多路溫度的測(cè)控，但價(jià)格昂貴。 針對(duì)目前市場(chǎng)的現(xiàn)狀，本課題提出了一種可滿足要求、可擴(kuò)展的并且性價(jià)比高的單片機(jī)多路測(cè)溫系統(tǒng)。通過(guò)溫度傳感器 DS18B20 采集，然后通過(guò) C51 單片機(jī)處理并在數(shù)碼管上顯示，可以采集室內(nèi)或溫室中四處不同位置的溫度，用四個(gè)數(shù)碼管來(lái)顯示。第一個(gè)數(shù)碼管顯示所采集的是哪一路，哪個(gè)通道。后三個(gè)數(shù)碼管顯示所采集通道的溫度值，精確到0.1度。 2 系統(tǒng)的實(shí)現(xiàn)及相關(guān)技術(shù) 2.1．系統(tǒng)的實(shí)現(xiàn) 整個(gè)控制系統(tǒng)采用AT89C51芯片，采用多線連接，就是四個(gè)DS1820分別連接到單片機(jī)的四個(gè)IO口，采集到的溫度結(jié)果通過(guò)串口通信，然后芯片將采集到的數(shù)據(jù)處理，在外部顯示器顯示出來(lái)，并且能夠?qū)崿F(xiàn)外部鍵盤(pán)的控制。溫度在LED液晶顯示屏顯示出來(lái)后，通過(guò)軟件編程確保系統(tǒng)有一定的抗干擾能力。這種方案雖然占用單片機(jī)的四個(gè)IO口，但在單片機(jī)IO口不緊缺的情況下采用這種方案大大的簡(jiǎn)化了編程難度，縮短了設(shè)計(jì)周期，同時(shí)也能保證系統(tǒng)的穩(wěn)定。多線連接方案的框圖如“圖1-1”所示 DS1820 DS1820 DS1820 DS1820 AT89C51單片機(jī) P1.0 P1.1 P1.2 P1.3 P3.4 顯示單元 按鍵控制單元 圖1-1 DS1820多線連接方案 2.2.AT89C51單片機(jī)簡(jiǎn)介 AT89C51是一種帶4K字節(jié)FLASH存儲(chǔ)器（FPEROM—Flash Programmable and Erasable Read Only Memory）的低電壓、高性能CMOS 8位微處理器，俗稱單片機(jī)。AT89C2051是一種帶2K字節(jié)閃存可編程可擦除只讀存儲(chǔ)器的單片機(jī)。單片機(jī)的可擦除只讀存儲(chǔ)器可以反復(fù)擦除1000次。該器件采用ATMEL高密度非易失存儲(chǔ)器制造技術(shù)制造，與工業(yè)標(biāo)準(zhǔn)的MCS-51指令集和輸出管腳相兼容。由于將多功能8位CPU和閃存存儲(chǔ)器組合在單個(gè)芯片中，ATMEL的AT89C51是一種高效微控制器，AT89C2051是它的一種精簡(jiǎn)版本。AT89C51單片機(jī)為很多嵌入式控制系統(tǒng)提供了一種靈活性高且價(jià)廉的方案。外形及引腳排列如圖“圖1-2”所示 圖1-2 AT89C51引腳圖 主要特性： ·與MCS-51 兼容 　　·4K字節(jié)可編程FLASH存儲(chǔ)器 　　·壽命：1000寫(xiě)/擦循環(huán) 　　·數(shù)據(jù)保留時(shí)間：10年 　　·全靜態(tài)工作：0Hz-24MHz 　　·三級(jí)程序存儲(chǔ)器鎖定 　　·128×8位內(nèi)部RAM 　　·32可編程I/O線 　　·兩個(gè)16位定時(shí)器/計(jì)數(shù)器 　　·5個(gè)中斷源 　　·可編程串行通道 　　·低功耗的閑置和掉電模式 ·片內(nèi)振蕩器和時(shí)鐘電路 管腳說(shuō)明： VCC：供電電壓。 GND：接地。 P0口：P0口為一個(gè)8位漏極開(kāi)路雙向I/O口，每腳可吸收8TTL門(mén)電流。當(dāng)P0口的管腳先要寫(xiě)入高電平，被定義為高阻輸入。P0能夠用于外部程序數(shù)據(jù)存儲(chǔ)器，它可以被定義為低八位數(shù)據(jù)或地址總線。在FIASH編程時(shí)，P0 口作為原碼輸入口，當(dāng)FIASH進(jìn)行校驗(yàn)時(shí)，P0輸出原碼，此時(shí)P0外部必須被拉高。 P1口：P1口是一個(gè)內(nèi)部提供上拉電阻的8位雙向I/O口，P1口緩沖器能接收輸出4TTL門(mén)電流。P1口管腳寫(xiě)入高電平后，被內(nèi)部上拉為高，可用作輸入，P1口被外部下拉為低電平時(shí)，將輸出電流，這是由于內(nèi)部上拉的緣故。在FLASH編程和校驗(yàn)時(shí)，P1口作為高八位地址接收。 P2口：P2口為一個(gè)內(nèi)部上拉電阻的8位雙向I/O口，P2口緩沖器可接收，輸出4個(gè)TTL門(mén)電流，當(dāng)P2口被寫(xiě)入高電平時(shí)，其管腳被內(nèi)部上拉電阻拉高，且作為輸入。并因此作為輸入時(shí)，P2口的管腳被外部拉低，將輸出電流。這是由于內(nèi)部上拉的緣故。P2口當(dāng)用于外部程序存儲(chǔ)器或16位地址外部數(shù)據(jù)存儲(chǔ)器進(jìn)行存取時(shí)，P2口輸出地址的高八位。在給出地址“1”時(shí)，它利用內(nèi)部上拉優(yōu)勢(shì)，當(dāng)對(duì)外部八位地址數(shù)據(jù)存儲(chǔ)器進(jìn)行讀寫(xiě)時(shí)，P2口輸出其特殊功能寄存器的內(nèi)容。P2口在FLASH編程和校驗(yàn)時(shí)接收高八位地址信號(hào)和控制信號(hào)。 P3口：P3口管腳是8個(gè)帶內(nèi)部上拉電阻的雙向I/O口，可接收輸出4個(gè)TTL門(mén)電流。當(dāng)P3口寫(xiě)入高電平后，它們被內(nèi)部上拉為高電平，并用作輸入。作為輸入，由于外部下拉為低電平，P3口將輸出電流（ILL）這是由于上拉的緣故。 RST：復(fù)位輸入。當(dāng)振蕩器復(fù)位器件時(shí)，要保持RST腳兩個(gè)機(jī)器周期的高電平時(shí)間。 ALE/PROG：當(dāng)訪問(wèn)外部存儲(chǔ)器時(shí)，地址鎖存允許的輸出電平用于鎖存地址的地位字節(jié)。在FLASH編程期間，此引腳用于輸入編程脈沖。在平時(shí)，ALE端以不變的頻率周期輸出正脈沖信號(hào)，此頻率為振蕩器頻率的1/6。因此它可用作對(duì)外部輸出的脈沖或用于定時(shí)目的。然而要注意的是：每當(dāng)用作外部數(shù)據(jù)存儲(chǔ)器時(shí)，將跳過(guò)一個(gè)ALE脈沖。如想禁止ALE的輸出可在SFR8EH地址上置0。此時(shí)， ALE只有在執(zhí)行MOVX，MOVC指令是ALE才起作用。另外，該引腳被略微拉高。如果微處理器在外部執(zhí)行狀態(tài)ALE禁止，置位無(wú)效。 /PSEN：外部程序存儲(chǔ)器的選通信號(hào)。在由外部程序存儲(chǔ)器取指期間，每個(gè)機(jī)器周期兩次/PSEN有效。但在訪問(wèn)外部數(shù)據(jù)存儲(chǔ)器時(shí)，這兩次有效的/PSEN信號(hào)將不出現(xiàn)。 /EA/VPP：當(dāng)/EA保持低電平時(shí)，則在此期間外部程序存儲(chǔ)器（0000H-FFFFH），不管是否有內(nèi)部程序存儲(chǔ)器。注意加密方式1時(shí)，/EA將內(nèi)部鎖定為RESET；當(dāng)/EA端保持高電平時(shí)，此間內(nèi)部程序存儲(chǔ)器。在FLASH編程期間，此引腳也用于施加12V編程電源（VPP）。 XTAL1：反向振蕩放大器的輸入及內(nèi)部時(shí)鐘工作電路的輸入。 XTAL2：來(lái)自反向振蕩器的輸出。 2.3.DS1820簡(jiǎn)介 DALLAS最新單線數(shù)字溫度傳感器DS18B20簡(jiǎn)介新的"一線器件"體積更小、適用電壓更寬、更經(jīng)濟(jì) Dallas 半導(dǎo)體公司的數(shù)字化溫度傳感器DS1820是世界上第一片支持 "一線總線"接口的溫度傳感器。一線總線獨(dú)特而且經(jīng)濟(jì)的特點(diǎn)，使用戶可輕松地組建傳感器網(wǎng)絡(luò)，為測(cè)量系統(tǒng)的構(gòu)建引入全新概念。DS18B20 "一線總線"數(shù)字化溫度傳感器 同DS1820一樣，DS18B20也 支持"一線總線"接口，測(cè)量溫度范圍為 -55°C~+125°C，在-10~+85°C范圍內(nèi),精度為±0.5°C?，F(xiàn)場(chǎng)溫度直接以"一線總線"的數(shù)字方式傳輸，大大提高了系統(tǒng)的抗干擾性。 適合于惡劣環(huán)境的現(xiàn)場(chǎng)溫度測(cè)量，如：環(huán)境控制、設(shè)備或過(guò)程控制、測(cè)溫類消費(fèi)電子產(chǎn)品等。與前一代產(chǎn)品不同，新的產(chǎn)品支持3V~5.5V的電壓范圍，使系統(tǒng) 設(shè)計(jì)更靈活、方便。而且新一代產(chǎn)品更便宜，體積更小。DS18B20可以程序設(shè)定9~12位的分辨率，精度為±0.5°C?？蛇x更小的封裝方式，更寬的電壓適用范圍。分辨率設(shè)定，及用戶設(shè)定的報(bào)警溫度存儲(chǔ)在 EEPROM中，掉電后依然保存。DS18B20的性能是新一代產(chǎn)品中最好的！性能價(jià)格比也非常出色！ DS1820的新性能: (1)?可用數(shù)據(jù)線供電，電壓范圍：3.0~5.5V； (2)?測(cè)溫范圍：-55~+125℃，在-10~+85℃時(shí)精度為±0.5℃； (3)?可編程的分辨率為9~12位，對(duì)應(yīng)的可分辨溫度分別為0.5℃、0.25℃、0.125℃和0.0625℃； (4)?12位分辨率時(shí)最多在750ms內(nèi)把溫度值轉(zhuǎn)換為數(shù)字； (5)?負(fù)壓特性：電源極性接反時(shí)，溫度計(jì)不會(huì)因發(fā)熱而燒毀，但不能正常工作。 DS1820的外形 DS18B20內(nèi)部結(jié)構(gòu)主要由四部分組成：64位光刻ROM、溫度傳感器、非揮發(fā)的溫度報(bào)警觸發(fā)器TH和TL、配置寄存器。DS18B20的管腳排列如“圖1-3”所示。內(nèi)部結(jié)構(gòu)如“圖1-4”所示 ?? 圖1-3 DS18B20外形圖 (1)?