數(shù)字式溫濕度檢測(cè)系統(tǒng)的設(shè)計(jì)的中英文文獻(xiàn)

1、附 錄：外文資料與中文翻譯外文資料：DS1820FEATURES Unique 1WireTM interface requires only one port pin for communication Multidrop capability simplifies distributed temperature sensing applications Requires no external components Can be powered from data line Zero standby power required Measures temperatures from 55C

2、 to +125C in 0.5C increments. Fahrenheit equivalent is 67F to +257F in 0.9F increments Temperature is read as a 9bit digital value. Converts temperature to digital word in 200 ms (typ.) Userdefinable, nonvolatile temperature alarm settings Alarm search command identifies and addresses devices whose

3、temperature is outside of programmed limits (temperature alarm condition) Applications include thermostatic controls, industrial systems, consumer products, thermometers, or any thermally sensitive systemDESCRIPTIONThe DS1820 Digital Thermometer provides 9bit temperature readings which indicate the

4、temperature of the device. Information is sent to/from the DS1820 over a 1Wire interface, so that only one wire (and ground) needs to be connected from a central microprocessor to a DS1820. Power for reading, writing, and performing temperature conversions can be derived from the data line itself wi

5、th no need for an external power source. Because each DS1820 contains a unique silicon serial number, multiple DS1820s can exist on the same 1Wire bus. This allows for placing temperature sensors in many different places. Applications where this feature is useful include HVAC environmental controls,

6、 sensing temperatures inside buildings, equipment or machinery, and in process monitoring and control.DETAILED PIN DESCRIPTIONOVERVIEWThe block diagram of Figure 1 shows the major components of the DS1820. The DS1820 has three main data components: 1) 64bit lasered ROM, 2) temperature and sensor, 3)

7、 nonvolatile temperature alarm triggers TH and TL. The device derives its power from the 1Wire communication line by storing energy on an internal capacitor during periods of time when the signal line is high and continues to operate off this power source during the low times of the 1Wire line until

8、 it returns high to replenish the parasite (capacitor) supply. As an alternative, the DS1820 may also be powered from an external 5 volts supply.Communication to the DS1820 is via a 1Wire port. With the 1Wire port, the memory and control functions will not be available before the ROM function protoc

9、ol has been established. The master must first provide 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 64bit lasered ROM portion of each device and can single out a specific device if many are present on the

10、1Wire line as well as indicate to the Bus Master how many and what types of devices are present. After a ROM function sequence has been successfully executed, the memory and control functions are accessible and the master may then provide any one of the six memory and control function commands. One

11、control function command instructs the DS1820 to perform a temperature measurement. The result of this measurement will be placed in the DS1820s scratchpad memory, and may be read by issuing a memory function command which reads the contents of the scratchpad memory. The temperature alarm triggers T

12、H and TL consist of one byte EEPROM each. If the alarm search command is not applied to the DS1820, these registers may be used as general purpose user memory. Writing TH and TL is done using a memory function command. Read access to these registers is through the scratchpad. All data is read and wr

13、itten least significant bit first.The block diagram (Figure 1) shows the parasite powered circuitry. This circuitry “steals” power whenever the I/O or VDD pins are high. I/O will provide sufficient power as long as the specified timing and voltage requirements are met (see the section titled “1Wire

14、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, 2) the ROM may be read in absence of normal power. In order for the DS1820 to be able to perform accurate temperature conversions, sufficient p

15、ower must be provided over the I/O line when a temperature conversion is taking place. Since the operating current of the DS1820 is up to 1 mA, the I/O line will not have sufficient drive due to the 5K pullup resistor. This problem is particularly acute if several DS1820s are on the same I/O and att

16、empting to convert simultaneously.There are two ways to assure that the DS1820 has sufficient supply current during its active conversion cycle. The first is to provide a strong pullup on the I/O line whenever temperature conversions or copies to the E2 memory are taking place. This may be accomplis

17、hed by using a MOSFET to pull the I/O line directly to the power supply as shown in Figure 2. The I/O line must be switched over to the strong pullup within 10 ms maximum after issuing any protocol that involves copying to the E2 memory or initiates temperature conversions. When using the parasite p

18、ower mode, the VDD pin must be tied to ground. Another method of supplying current to the DS1820 is through the use of an external 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 I/O line, and the bus master need not be t

19、ied up holding that line high during temperature conversions. This allows other data traffic on the 1Wire bus during the conversion time. In addition, any number of DS1820s may be placed on the 1Wire bus, and if they all use external power, they may all simultaneously perform temperature conversions

20、 by issuing the Skip ROM command and then issuing the Convert T command. Note that as long as the external power supply is active, the GND pin may not be floating. The use of parasite power is not recommended above 100C, since it may not be able to sustain communications given the higher leakage cur

21、rents the DS1820 exhibits at these temperatures. For applications in which such temperatures are likely, it is strongly recommended that VDD be applied to the DS1820. For situations where the bus master does not know whether the DS1820s on the bus are parasite powered or supplied with external VDD,

22、a provision is made in the DS1820 to signal the power supply scheme used. The bus master can determine if any DS1820s are on the bus which require the strong pullup by sending a Skip.ROM protocol, then issuing the read power supply command. After this command is issued, the master then issues read t

23、ime slots.The DS1820 will send back “0” on the 1Wire bus if it is parasite powered; it will send back a “1” if it is powered from the VDD pin. If the master receives a “0”, it knows that it must supply the strong pullup on the I/O line during temperature conversions. See “Memory Command Functions” s

24、ection for more detail on this command protocol.OPERATION MEASURING TEMPERATUREThe DS1820 measures temperature through the use of an onboard proprietary temperature measurement technique. A block diagram of the temperature measurement circuitry is shown in Figure 4. The DS1820 measures temperature b

25、y counting the number of clock cycles that an oscillator with a low temperature coefficient goes through during a gate period determined by a high temperature coefficient oscillator. The counter is preset with a base count that corresponds to 55C. If the counter reaches zero before the gate period i

26、s over, the temperature register, which is also preset to the 55C value, is incremented, indicating that the temperature is higher than 55C. At the same time, the counter is then preset with a value determined by the slope accumulator circuitry. This circuitry is needed to compensate for the parabol

27、ic behavior of the oscillators over temperature. The counter is then clocked again until it reaches zero.If the gate period is still not finished, then this process repeats. The slope accumulator is used to compensate for the nonlinear behavior of the oscillators over temperature, yielding a high re

28、solution temperature measurement. This is done by changing the number of counts necessary for the counter to go through for each incremental degree in temperature. To obtain the desired resolution, therefore, both the value of the counter and the number of counts per degree C (the value of the slope

29、 accumulator) at a given temperature must be known.Internally, this calculation is done inside the DS1820 to provide 0.5C resolution. The temperature reading is provided in a 16bit, signextended twos complement reading. Table 1 describes the exact relationship of output data to measured temperature.

30、 The data is transmitted serially over the 1Wire interface. The DS1820 can measure temperature over the range of 55C to +125C in 0.5C increments. For Fahrenheit usage, a lookup table or conversion factor must be used.Note that temperature is represented in the DS1820 in terms of a 1/2C LSB, yielding

31、 the following 9bit format:The most significant (sign) bit is duplicated into all of the bits in the upper MSB of the twobyte temperature register in memory. This “signextension” yields the 16bit temperature readings as shown in Table 1. Higher resolutions may be obtained by the following procedure.

32、 First, read the temperature, and truncate the 0.5C bit (the LSB) from the read value. This value is TEMP_READ. The value left in the counter may then be read. This value is the count remaining (COUNT_REMAIN) after the gate period has ceased. The last value needed is the number of counts per degree

33、C (COUNT_PER_C) at that temperature. The actual temperature may be then be calculated by the user using the following:1WIRE BUS SYSTEMThe 1Wire bus is a system which has a single bus master and one or more slaves. The DS1820 behaves as a slave. The discussion of this bus system is broken down into t

34、hree topics: hardware configuration, transaction sequence, and 1Wire signaling (signal types and timing).HARDWARE CONFIGURATION The 1Wire bus has only a single line by definition; it is important that each device on the bus be able to drive it at the appropriate time. To facilitate this, each device

35、 attached to the 1Wire bus must have open drain or 3state outputs.The 1Wire port of the DS1820 (I/Opin) is open drain with an internal circuit equivalent to that shown in Figure 9. A multidrop bus consists of a 1Wire bus with multiple slaves attached. The 1Wire bus requires a pullup resistor of appr

36、oximately 5KW.The idle state for the 1Wire bus is high. If for any reason a transaction needs to be suspended, the bus MUST be left in the idle state if the transaction is to resume. Infinite recovery time can occur between bits so long as the 1Wire bus is in the inactive (high) state during the rec

37、overy period. If this does not occur and the bus is left low for more than 480 ms, all components on the bus will be reset. TRANSACTION SEQUENCEThe protocol for accessing the DS1820 via the 1Wire port is as follows: Initialization ROM Function Command Memory Function Command Transaction/DataINITIALI

38、ZATIONAll transactions on the 1Wire bus begin with an initialization sequence. The initialization sequence consists of a reset pulse transmitted by the bus master followed by presence pulse(s) transmitted by the slave(s).The presence pulse lets the bus master know that the DS1820 is on the bus and i

39、s ready to operate. For more details, see the “1Wire Signaling” section.ROM FUNCTION COMMANDSOnce the bus master has detected a presence, it can issue one of the five ROM function commands. All ROM function commands are 8bits long. A list of these commands follows (refer to flowchart in Figure 6):Re

40、ad ROM 33hThis command allows the bus master to read the DS1820s 8bit family code, unique 48bit serial number,and 8bit CRC. This command can only be used if there is a single DS1820 on the bus. If more than one slave is present on the bus, a data collision will occur when all slaves try to transmit

41、at the same time (open drain will produce a wired AND result).Match ROM 55hThe match ROM command, followed by a 64bit ROM sequence, allows the bus master to address a specific DS1820 on a multidrop bus. Only the DS1820 that exactly matches the 64bit ROM sequence will respond to the following memory

42、function command. All slavesthat do not match the 64bit ROM sequence will wait for a reset pulse. This command can be used with a single or multiple devices on the bus.Skip ROM CChThis command can save time in a single drop bus system by allowing the bus master to access the memory functions without

43、 providing the 64bit ROM code. If more than one slave is present on the bus and a read command is issued following the Skip ROM command, data collision will occur on the bus as multiple slaves transmit simultaneously (open drain pulldowns will produce a wired AND result).Search ROM F0hWhen a system

44、is initially brought up, the bus master might not know the number of devices on the 1Wire bus or their 64bit ROM codes. The search ROM command allows the bus master to use a process of elimination to identify the 64bit ROM codes of all slave devices on the bus.中文翻譯：DS1820特性：獨(dú)特的單線接口，只需1 個(gè)接口引腳即可通信；多點(diǎn)（

45、multidrop）能力使分布式溫度檢測(cè)應(yīng)用得以簡(jiǎn)化；不需要外部元件；可用數(shù)據(jù)線供電；不需備份電源；測(cè)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 F，增量值為0.9 F；以9位數(shù)字值方式讀出溫度；在1秒（典型值）內(nèi)把溫度變換為數(shù)字；用戶可定義的，非易失性的溫度告警設(shè)置；告警搜索命令識(shí)別和尋址溫度在編定的極限之外的器件（溫度告警情況）；應(yīng)用范圍包括恒溫控制，工業(yè)系統(tǒng)，消費(fèi)類產(chǎn)品，溫度計(jì)或任何熱敏系統(tǒng)。詳細(xì)說明DS1820有三個(gè)主要的數(shù)據(jù)部件：1）64位激光lasered ROM；2）溫度靈敏元件，和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

46、得其電源，在信號(hào)線為高電平的時(shí)間周期內(nèi)，把能量貯存在內(nèi)部的電容器中，在單信號(hào)線為低電平的時(shí)間期內(nèi)斷開此電源，直到信號(hào)線變?yōu)楦唠娖街匦陆由霞纳娙荩╇娫礊橹?。作為另一種可供選擇的方法，DS1820也可以用外部5V電源供電。與DS1820 的通信經(jīng)過一個(gè)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(jī)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)；5）Alarm Search(告警搜索)；這些命令對(duì)每一器件的64位激光ROM

47、 部分進(jìn)行操作，如果在單線上有許多器件，那么可以挑選出一個(gè)特定的器件，并給總線上的主機(jī)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(jī)可以提供六種存貯器和控制操作命令之一。一個(gè)控制操作命令指示DS1820 完成溫度測(cè)量。該測(cè)量的結(jié)果將放入DS1820 的高速暫存（便箋式）存貯器（Scratchpad memory），通過發(fā)出讀暫存存儲(chǔ)器內(nèi)容的存儲(chǔ)器操作命令可以讀出此結(jié)果。每一溫度告警觸發(fā)器TH和TL構(gòu)成一個(gè)字節(jié)的EEPROM。如果不對(duì)DS1820 施加告警搜索命令，這些寄存器可用作通用用戶存儲(chǔ)器使用存儲(chǔ)器，操作命令可以寫TH 和TL 對(duì)這些寄存器的

48、讀訪問。所有數(shù)據(jù)均以最低有效位在前的方式被讀寫。寄生電源方框圖(圖1)示出寄生電源電路。當(dāng)I/O或VDD 引腳為高電平時(shí)，這個(gè)電路便“取”得電源。只要符合指定的定時(shí)和電壓要求，I/O將提供足夠的功率（標(biāo)題為“單總線系統(tǒng)”一節(jié)）。寄生電源的優(yōu)點(diǎn)是雙重的：1）利用此引腳，遠(yuǎn)程溫度檢測(cè)無(wú)需本地電源；2）缺少正常電源條件下也可以讀ROM；為了使DS1820能完成準(zhǔn)確的溫度變換，當(dāng)溫度變換發(fā)生時(shí)，I/O 線上必須提供足夠的功率。因?yàn)镈S1820 的工作電流高達(dá)1mA ，5K 的上拉電阻將使I/O 線沒有足夠的驅(qū)動(dòng)能力。如果幾個(gè)SD1820 在同一條I/O 線上而且同時(shí)變換，那么這一問題將變得特別尖銳。有

49、兩種方法確保DS1820 在其有效變換期內(nèi)得到足夠的電源電流。第一種方法是發(fā)生溫度變換時(shí)，在I/O 線上提供一強(qiáng)的上拉。如圖2所示，通過使用一個(gè)MOSFET 把I/O 線直接拉到電源可達(dá)到這一點(diǎn)。當(dāng)使用寄生電源方式時(shí)VDD 引腳必須連接到地。向DS1820 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(diǎn)是在I/O 線上不要求強(qiáng)的上拉?？偩€上主機(jī)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(shí)間內(nèi)其它數(shù)據(jù)在單線上傳送。此外，在單線總線上可以放置任何數(shù)目的DS1820 ，而且如果它們都使用外部電源，那么通過發(fā)出跳過（Skip） ROM 命令和接著發(fā)

50、出變換（Convert） T 命令，可以同時(shí)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。在總線上主機(jī)不知道總線上DS1820 是寄生電源供電還是外部VDD 供電的情況下，在DS1820 內(nèi)采取了措施來(lái)通知采用的供電方案?？偩€上主機(jī)通過發(fā)出跳過（Skip）ROM 的操作約定，然后發(fā)出讀電源命令，可以決定是否有需要強(qiáng)上拉的DS1820 在總線上。在此命令發(fā)出后，主機(jī)接著發(fā)出讀時(shí)間片。如果是寄生供電，DS1820 將在單線總線上送回“0”；如果由VDD 引腳供電，它將送回1。如果主機(jī)接收到一個(gè)“0”，它知道它必須在溫度變換期間在I/O 線上供一個(gè)強(qiáng)的上拉。有關(guān)此命令約定的詳細(xì)說明見存貯器命令功能一節(jié)。運(yùn)用測(cè)量溫度SDS1820 通過使用在板（on-board）溫度測(cè)量專利技術(shù)來(lái)測(cè)量溫度。溫度測(cè)量電路的方框圖見圖4 所示。DS1820 通過門開通期間內(nèi)低溫度系數(shù)振蕩器經(jīng)歷的時(shí)鐘周期個(gè)數(shù)計(jì)數(shù)來(lái)測(cè)量溫度，如果在門開通期結(jié)束前計(jì)數(shù)器達(dá)到零，那么溫度寄存器它也被予置到-55的數(shù)值將增量，指示溫度高于-55。同時(shí)，計(jì)數(shù)器用鈄率累加器電路所決定的值進(jìn)行予置。為了對(duì)遵循拋物線規(guī)律的振蕩器溫度特性進(jìn)行補(bǔ)償，這