数字式温湿度检测系统的设计的中英文文献.doc

1、附 录：外文资料与中文翻译外文资料：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 accomplished by using a MOSFET to pull the I/O line directly to the power supply as shown in Figure 2. The I