單片機畢業(yè)設計外文翻譯--ds18b20

1、<p><b>　　外文資料原文</b></p><p><b>　　DS18B20</b></p><p>　　1.1 DESCRIPTION</p><p>　　The DS18B20 Digital Thermometer provides 9 to 12-bit (configurable) temp

2、erature readings which indicate the temperature of the device.</p><p>　　Information is sent to/from the DS18B20 over a 1-Wire interface, so that only one wire (and ground) needs to be connected from a centra

3、l microprocessor to a DS18B20. Power for reading, writing, and performing temperature conversions can be derived from the data line itself with no need for an external power source.</p><p>　　Because each DS1

4、8B20 contains a unique silicon serial number, multiple DS18B20s can exist on the same 1-Wire bus. This allows for placing temperature sensors in many different places. Applications where this feature is useful include HV

5、AC environmental controls, sensing temperatures inside buildings, equipment or machinery, and process monitoring and control.</p><p>　　1.2 FEATURES</p><p>　　Unique 1-WireTM interface requires

6、only one port pin for communication</p><p>　　Multidrop capability simplifies distributed temperature sensing applications</p><p>　　Requires no external components</p><p>　　Can be po

7、wered from data line. Power supply range is 3.0V to 5.5V</p><p>　　Zero standby power required</p><p>　　Measures temperatures from -55°C to+125°C. Fahrenheit equivalent is -67°F to

8、+257°F</p><p>　　0.5?C accuracy from -10°C to +85°C</p><p>　　Thermometer resolution is programmable from 9 to 12 bits</p><p>　　Converts 12-bit temperature to digital w

9、ord in 750 ms (max.)</p><p>　　User-definable, nonvolatile temperature alarm settings</p><p>　　Alarm search command identifies and addresses devices whose temperature is outside of programmed lim

10、its (temperature alarm condition)</p><p>　　Applications include thermostatic controls, industrial systems, consumer products, thermometers, or any thermally sensitive system</p><p>　　1.3 PIN A

11、SSIGNMENT</p><p>　　DETAILED PIN DESCRIPTION Table 1</p><p>　　DS18B20Z (8-pin SOIC) and DS18P20P (TSOC): All pins not specified in this table are not to be connected.</p><p>　　1.4

12、OVERVIEW</p><p>　　The block diagram of Figure 1 shows the major components of the DS18B20. The DS18B20 has four main data components: 1) 64-bit lasered ROM, 2) temperature sensor, 3) nonvolatile temperature

13、alarm triggers TH and TL, and 4) a configuration register. The device derives its power from the 1-Wire communication line by storing energy on an internal capacitor during periods of time when the signal line is high an

14、d continues to operate off this power source during the low times of the 1-Wire line until </p><p>　　powered from an external 3V - 5.5V supply.</p><p>　　DS18B20 BLOCK DIAGRAM Figure 1</p>

15、<p>　　Communication to the DS18B20 is via a 1-Wire port. With the 1-Wire port, the memory and control functions will not be available before the ROM function protocol has been established. The master must first pro

16、vide one of five ROM function commands: 1) Read ROM, 2) Match ROM, 3) Search ROM, 4)Skip ROM, or 5) Alarm Search. These commands operate on the 64-bit lasered ROM portion of each device and can single out a specific devi

17、ce if many are present on the 1-Wire line as well as indicate to the bus</p><p>　　One control function command instructs the DS18B20 to perform a temperature measurement. The result of this measurement will

18、be placed in the DS18B20’s scratch-pad memory, and may be read by issuing a memory function command which reads the contents of the scratchpad memory. The temperature alarm triggers TH and TL consist of 1 byte EEPROM eac

19、h. If the alarm search command is not applied to the DS18B20, these registers may be used as general purpose user memory. The scratchpad also contains a co</p><p>　　and the configuration byte is done using a

20、 memory function command. Read access to these registers is through the scratchpad. All data is read and written least significant bit first.</p><p>　　1.5 PARASITE POWER</p><p>　　The block dia

21、gram (Figure 1) shows the parasite-powered circuitry. This circuitry “steals” power whenever the DQ or VDD pins are high. DQ will provide sufficient power as long as the specified timing and voltage requirements are met

22、(see the section titled “1-Wire Bus System”). The advantages of parasite power are twofold: 1) by parasiting off this pin, no local power source is needed for remote sensing of temperature, and 2) the ROM may be read in

23、absence of normal power.</p><p>　　In order for the DS18B20 to be able to perform accurate temperature conversions, sufficient power must be provided over the DQ line when a temperature conversion is taking p

24、lace. Since the operating current of the DS18B20 is up to 1.5 mA, the DQ line will not have sufficient drive due to the 5k pullup resistor. This problem is particularly acute if several DS18B20s are on the same DQ and at

25、tempting to convert simultaneously.</p><p>　　There are two ways to assure that the DS18B20 has sufficient supply current during its active conversion cycle. The first is to provide a strong pull up on the DQ

26、 line whenever temperature conversions or copies to the E2 memory are taking place. This may be accomplished by using a MOSFET to pull the DQ line directly to the power supply as shown in Figure 2. The DQ line must be sw

27、itched over to the strong pull up within 10 s maximum after issuing any protocol that involves copying to the E2 memor</p><p>　　Another method of supplying current to the DS18B20 is through the use of an ext

28、ernal power supply tied to the VDD pin, as shown in Figure 3. The advantage to this is that the strong pullup is not required on the DQ line, and the bus master need not be tied up holding that line high during temperatu

29、re conversions.This allows other data traffic on the 1-Wire bus during the conversion time. In addition, any number of DS18B20s may be placed on the 1-Wire bus, and if they all use external power, they</p><p&g

30、t;　　The use of parasite power is not recommended above 100?C, since it may not be able to sustain communications given the higher leakage currents the DS18B20 exhibits at these temperatures. For applications in which suc

31、h temperatures are likely, it is strongly recommended that VDD be applied to the DS18B20.</p><p>　　For situations where the bus master does not know whether the DS18B20s on the bus are parasite powered or su

32、pplied with external VDD, a provision is made in the DS18B20 to signal the power supply scheme used. The bus master can determine if any DS18B20s are on the bus which require the strong Pull up by sending a Skip ROM prot

33、ocol, then issuing the read power supply command. After this command is issued, the master then issues read time slots. The DS18B20 will send back “0” on the 1-Wire bus if </p><p>　　See “Memory Command Funct

34、ions” section for more detail on this command protocol.</p><p>　　STRONG PULLUP FOR SUPPLYING DS18B20 DURING TEMPERATURE</p><p>　　CONVERSION Figure 2</p><p>　　USING VDD TO SUPPLY TEM

35、PERATURE CONVERSION CURRENT Figure 3</p><p>　　1.6 OPERATION - ALARM SIGNALING</p><p>　　After the DS18B20 has performed a temperature conversion, the temperature value is compared to the trigge

36、r values stored in TH and TL. Since these registers are 8-bit only, bits 9-12 are ignored for comparison. The most significant bit of TH or TL directly corresponds to the sign bit of the 16-bit temperature register. If t

37、he result of a temperature measurement is higher than TH or lower than TL, an alarm flag inside the device is set. This flag is updated with every temperature measurement. As </p><p>　　1.7 64-BIT LASERED R

38、OM</p><p>　　Each DS18B20 contains a unique ROM code that is 64-bits long. The first 8 bits are a 1-Wire family code (DS18B20 code is 28h). The next 48 bits are a unique serial number. The last 8 bits are a C

39、RC of the first 56 bits. (See Figure 4.) The 64-bit ROM and ROM Function Control section allow the DS18B20 to operate as a 1-Wire device and follow the 1-Wire protocol detailed in the section “1-Wire Bus System”. The fun

40、ctions required to control sections of the DS18B20 are not accessible until the ROM f</p><p>　　64-BIT LASERED ROM Figure 4</p><p>　　1.8 CRC GENERATION</p><p>　　The DS18B20 has an

41、8-bit CRC stored in the most significant byte of the 64-bit ROM. The bus master can compute a CRC value from the first 56-bits of the 64-bit ROM and compare it to the value stored within the DS18B20 to determine if the R

42、OM data has been received error-free by the bus master. The equivalent polynomial function of this CRC is: </p><p>　　CRC = X8 + X5 + X4 + 1</p><p>　　The DS18B20 also generates an 8-bit CRC value

43、 using the same polynomial function shown above and provides this value to the bus master to validate the transfer of data bytes. In each case where a CRC is used for data transfer validation, the bus master must calcula

44、te a CRC value using the polynomial function given above and compare the calculated value to either the 8-bit CRC value stored in the 64-bit ROM portion of the DS18B20 (for ROM reads) or the 8-bit CRC value computed with

45、in the DS18B20 </p><p>　　The 1-Wire CRC can be generated using a polynomial generator consisting of a shift register and XOR gates as shown in Figure 5. Additional information about the Dallas 1-Wire Cyclic

46、Redundancy Check is available in Application Note 27 entitled “Understanding and Using Cyclic Redundancy Checks with Dallas Semiconductor Touch Memory Products”.</p><p>　　The shift register bits are initiali

47、zed to 0. Then starting with the least significant bit of the family code, 1bit at a time is shifted in. After the eighth bit of the family code has been entered, then the serial number is entered. After the 48th bit of

48、the serial number has been entered, the shift register contains the CRC value. Shifting in the 8 bits of CRC should return the shift register to all 0 s.</p><p>　　1.9 1-WIRE BUS SYSTEM</p><p>

49、　　The 1-Wire bus is a system which has a single bus master and one or more slaves. The DS18B20 behaves as a slave. The discussion of this bus system is broken down into three topics: hardware configuration, transaction s

50、equence, and 1-Wire signaling (signal types and timing).</p><p>　　WIRE CRC CODE Figure 5</p><p>　　2.0 TRANSACTION SEQUENCE</p><p>　　The protocol for accessing the DS18B20 via the

51、1-Wire port is as follows:</p><p>　?。?） Initialization</p><p>　?。?）ROM Function Command</p><p>　?。?） Memory Function Command</p><p>　　（4） Transaction/Data</p>&l

52、t;p><b>　　外文資料譯文</b></p><p><b>　　DS18B20</b></p><p><b>　　一 概述</b></p><p><b>　　1.1 一般說明</b></p><p>　　DS18B20 數字溫度計提供

53、9到12位溫度讀數,指示器件的溫度。</p><p>　　信息經過單線接口送入DS18B20 或從DS18B20 送出，因此從中央處理器到DS18B20 僅需連接一條線和地讀寫和完成溫度變換所需的電源可以由數據線本身提供而不需要外部電源。</p><p>　　因為每一個DS18B20 有唯一的系列號(silicon serial number),因此多個DS18B20 可以存在于同一條單線

54、總線上。這允許在許多不同的地方放置溫度靈敏器件。此特性的應用范圍包括HVAC環(huán)境控制，建筑物、設備或機械內的溫度檢測，以及過程監(jiān)視和控制中的溫度檢測。</p><p><b>　　1.2 特性</b></p><p>　　獨特的單線接口，只需1個接口引腳，即可通信。</p><p>　　多點(multidrop)能使分布式溫度檢測應用得以簡化

55、。</p><p><b>　　不需要外部元件。</b></p><p>　　可用數據線供電,供電電壓為3.0V到5.5V。</p><p><b>　　不需備份電源。</b></p><p>　　測量范圍從-55 至+125 增量值為0.5 等效的華氏溫度范圍是-67°F至257

56、6;F。</p><p>　　以9 或12位數字值方式讀出溫度。</p><p>　　在-10℃～+85℃時精度為±0.5℃。</p><p>　　12位分辨率時最多在750ms內把溫度值轉換為數字。</p><p>　　用戶可定義的非易失性的溫度告警設置。</p><p>　　告警搜索命令識別和尋址溫度在編

57、定的極限之外的器件溫度告警情況。</p><p>　　應用范圍包括恒溫控制工業(yè)系統消費類產品溫度計或任何熱敏系統。</p><p><b>　　1.3 引腳排列</b></p><p>　　1.4 詳細的引腳說明</p><p><b>　　1.5 詳細說明</b></p>&l

58、t;p>　　圖1 的方框圖表示DS18B20 的主要部件。DS18B20 有三個主要的數據部件：1)64 位激光 ROM；2)溫度靈敏元件；3)非易失性溫度告警觸發(fā)器TH 和TL 。器件從單線的通信線取得其電源，在信號線為高電平的時間周期內，把能量貯存在內部的電容器中，在單信號線為低電平的時間期內斷開此電源，直到信號線變?yōu)楦唠娖街匦陆由霞纳娙蓦娫礊橹埂Ｗ鳛榱硪环N可供選擇的方法DS18B20 也可用外部5V 電源供電。</p

59、><p>　　與DS18B20 的通信經過一個單線接口。在單線接口情況下，在ROM 操作未定建立之前不能使用存貯器和控制操作。主機必須首先提供五種ROM 操作命令之一：1 )Read ROM(讀ROM)， 2)Match ROM(符合ROM),3)Search ROM(搜索ROM),4)Skip ROM(跳過ROM),或5)Alarm Search(告警搜索) 。這些命令對每一器件的64 位激光ROM 部分進行操作。

60、如果在單線上有許多器件，那么可以挑選出一個特定的器件，并給總線上的主機指示存在多少器件及其類型。在成功地執(zhí)行了ROM 操作序列之后，可使用存貯器和控制操作，然后主機可以提供六種存貯器和控制操作命令之一。</p><p>　　一個控制操作命令指示DS18B20 完成溫度測量。該測量的結果將放入DS18B20 的高速暫存(便箋式)存貯器(Scratchpad memory )， 通過發(fā)出讀暫存存儲器內容的存儲器操作命

61、令可以讀出此結果。每一溫度告警觸發(fā)器TH 和TL 構成一個字節(jié)的EEPROM 。如果不對DS18B20 施加告警搜索命令,這些寄存器可用作通用用戶存儲器使用存儲器.操作命令可以寫TH 和TL。 對這些寄存器的讀訪問,通過便箋存儲器。所有數據均以最低有效位在前的方式被讀寫。</p><p>　　圖1 DS18B20的方框圖</p><p>　　1.5 寄生電源(parasite power

62、)</p><p>　　方框圖(圖1)示出寄生電源電路。當I/O 或VDD 引腳為高電平時，這個電路便取得電源。只要符合指定的定時和電壓要求，I/O 將提供足夠的功率（標題為“單總線系統”一節(jié)）。寄生電源的優(yōu)點是雙重的：1)利用此引腳，遠程溫度檢測無需本地電源，2)缺少正常電源條件下也可以讀ROM。</p><p>　　為了使DS18B20 能完成準確的溫度變換，當溫度變換發(fā)生時，I/O

63、線上必須提供足夠的功率。因為DS18B20 的工作電流高達1mA，5K 的上拉電阻將使I/O 線沒有足夠的驅動能力。如果幾個DS18B20 在同一條I/O 線上而且企圖同時變換，那么這一問題將變得特別尖銳。</p><p>　　有兩種方法確保DS18B20 在其有效變換期內得到足夠的電源電流。第一種方法是發(fā)生溫度變換時，在I/O 線上提供一強的上拉。如圖2 所示，通過使用一個MOSFET 把I/O 線直接拉到電源

64、可達到這一點。當使用寄生電源方式時VDD 引腳必須連接到地。</p><p>　　向DS18B20 供電的另外一種方法是通過使用連接到VDD 引腳的外部電源，如圖3 所示。這種方法的優(yōu)點是在I/O 線上不要求強的上拉?？偩€上主機不需向上連接便在溫度變換期間使線保持高電平。這就允許在變換時間內其它數據在單線上傳送。此外，在單線總線上可以放置任何數目的DS18B20， 而且如果它們都使用外部電源，那么通過發(fā)出跳過(S

65、kip) ROM 命令和發(fā)出變換(Convert) T 命令,可以同時完成溫度變換。注意只要外部電源處于工作狀態(tài)，GND （地）引腳不可懸空。</p><p>　　圖2 強上拉在溫度變換期內向DS18B20 供電</p><p>　　圖3 使用VDD 提供溫度變換所需電流</p><p>　　1.6 運用告警信號</p><p>　　在DS

66、18B20 完成溫度變換之后，溫度值與貯存在TH 和TL 內的觸發(fā)值相比較。因為這些寄存器僅僅是8 位，所以0.5 位在比較時被忽略。TH 或TL 的最高有較位直接對應于16位溫度寄存器的符號位。如果溫度測量的結果高于TH 或低于TL ，那么器件內告警標志將置位。每次溫度測量更新此標志。只要告警標志置位，DS18B20 將對告警搜索命令做出響應。這允許并聯連接許多DS18B20 ，同時進行溫度測量。如果某處溫度超過極限，那么可以識別出正

67、在告警的器件并立即將其讀出而不必讀出非告警的器件。</p><p>　　1.7 64 位激光ROM</p><p>　　每一DS18B20 包括一個唯一的64 位長的ROM 編碼。開紿的8 位是單線產品系列編碼(DS18B20 編碼是10h)。 接著的48 位是唯一的系列號。最后的8 位是開始56 位CRC （見圖4）。64位ROM 和ROM 操作控制部分允許DS18B20 作為一個單線

68、器件工作并遵循“單線總線系統”一節(jié)中所詳述的單線協議，直到ROM 操作協議被滿足。DS18B20 控制部分的功能是不可訪問的。單線總線主機必須首先操作五種ROM 操作</p><p>　　命令之一：1) Read ROM(讀ROM),2)Match ROM(匹配ROM),3)Search ROM(搜索ROM),4)Skip ROM(跳過ROM),或5)Alarm Search(告警搜索)。在成功地執(zhí)行了ROM 操

69、作序列之后，DS18B20 特定的功能便可訪問，然后總線上主機可提供六個存貯器和控</p><p><b>　　制能命令之一。</b></p><p>　　MSB LSB MSB LSB MSB LSB</p><p>　?。ㄗ罡哂行唬?（最低有效位）</p><p>　　圖4 64 位激

70、光ROM</p><p>　　1.8 CRC 產生</p><p>　　DS18B20 有一存貯在64 位ROM 的最高有效字節(jié)內的8 位CRC， 總線上的主機可以根據64 位ROM 的前56 位計算機CRC 的值并把它與存貯在DS18B20 內的值進行比較以決定ROM 的數據是否已被主機正確地接收。CRC 的等效多項式函數為：</p><p>　　CRC=X8

71、+X5+X4+1</p><p>　　DS18B20 也利用與上述相同的多項式函數產生一個8 位CRC 值并把此值提供給總線的主機以確認數據字節(jié)的傳送。在使用CRC 來確認數據傳送的每一種情況中，總線主機必須使用上面給出的多項式函數計算CRC 的值并把計算所得的值或者與存貯在DS18B20 的64 位ROM 部分中的8 位CRC值(ROM讀數),或者與DS18B20 中計算得到的8 位CRC 值(在讀暫存存貯器中

72、時,它作為第九個字節(jié)被讀出)進行比較。CRC 值的比較和是否繼續(xù)操作都由總線主機來決定，當存貯在DS18B20 內或由DS18B20 計算得到的CRC 值與總線主機產生的值不相符合時，在DS18B20 內沒有電路來阻止命令序列的繼續(xù)執(zhí)行。</p><p>　　總線CRC 可以使用如圖5 所示由一個移位寄存器和“異或”(XOR) 門組成的多項式產生器來產生.其它有關Dallas 公司單線循環(huán)冗余校驗的信息可參見標題

73、為“理解和使用Dallas 半導體公司接觸式存貯器產品”的應用注釋。</p><p>　　移位寄存器的所有位被初始化為零。然后從產品系列編碼的最低有效位開始，每次移入一位。當產品系列編碼的8 位移入以后，接著移入序列號。在序列號的第48 位進入之后，移位寄存器便包含了CRC 值。移入CRC 的8 位應該使移位寄存器返回至全零。</p><p>　　圖5 單線CRC 編碼</p>

74、<p>　　1.9 單線總線系統</p><p>　　單線總線是一種具有一個總線主機和一個或若干個從機(從屬器件)的系統，DS18B20起從機的作用。這種總線系統的討論分為三個題目：硬件接法，處理順序，以及單線信號（信號類型與定時）。</p><p><b>　　2.0 處理順序</b></p><p>　　經過單線接口訪問D