1、 本科生毕业设计（论文）外文翻译 译文题目： DS18B20 单线温度传感器 外文题目： DS18B20 Single - wire temperature sensor 学 院： 信息科学与工程学院 专业班级： 电子信息工程 0804 班 学生姓名： 指导教师： DS18B20 Single - wire temperature sensor 一 . FEATURES Unique 1-Wireinterface requires only one port pin for communication Each device has a unique 64-bit serial code s
2、tored in an onboard ROM Multidrop capability simplifies distributed temperature sensing applications Requires no external components Can be powered from data line. Power supply range is 3.0V to 5.5V Measures temperatures from 55C to +125C (67F to +257F) 0.5 C accuracy from 10C to +85C Thermometer re
3、solution is user-selectable from 9 to 12 bits Converts temperature to 12-bit digital word in 750ms (max.) User-definable nonvolatile (NV) alarm settings Alarm search command identifies and addresses devices whose temperature is outside of programmed limits (temperature alarm condition) Available in
4、8-pin SO (150mil), 8-pin SOP, and 3-pin TO-92 packages Software compatible with the DS1822 Applications include thermostatic controls, industrial systems, consumer products, thermometers, or any thermally sensitive 二 . DESCRIPTION The DS18B20 Digital Thermometer provides 9 to 12bit centigrade temper
5、ature measurements and has an alarm function with nonvolatile user-programmable upper and lower trigger points. The DS18B20 communicates over a 1-Wire bus that by definition requires only one data line (and ground) for communication with a central microprocessor. It has an operating temperature rang
6、e of 55C to +125Cand is accurate to 0.5 C over the range of 10C to +85C. In addition, the DS18B20 can derive powerdirectly from the data line (“parasite power”), eliminating the need for an external power supply. Each DS18B20 has a unique 64-bit serial code, which allows multiple DS18B20s to functio
7、n on the same 1wire bus； thus, it is simple to use one microprocessor to control many DS18B20s distributed over a large area. Applications that can benefit from this feature include HVAC environmental controls, temperature monitoring systems inside buildings, equipment or machinery, and process moni
8、toring and control systems. 三 . OVERVIEW Figure 1 shows a block diagram of the DS18B20, and pin descriptions are given in Table 1. The 64-bit ROM stores the devices unique serial code. The scratchpad memory contains the 2-byte temperature register that stores the digital output from the temperature
9、sensor. In addition, the scratchpad provides access to the 1-byte upper and lower alarm trigger registers (TH and TL), and the 1-byte configuration register. The configuration register allows the user to set the resolution of the temperature-to-digital conversion to 9, 10, 11, or 12 bits. The TH, TL
10、 and configuration registers are nonvolatile (EEPROM), so they will retain data when the device is powered down. The DS18B20 uses Dallas exclusive 1-Wire bus protocol that implements bus communication using one control signal. The control line requires a weak pullup resistor since all devices are li
11、nked to the bus via a 3-state or open-drain port (the DQ pin in the case of the DS18B20). In this bus system, the microprocessor (the master device) identifies and addresses devices on the bus using each devices unique 64-bit code. Because each device has a unique code, the number of devices that ca
12、n be addressed on one bus is virtually unlimited. The 1-Wire bus protocol, including detailed explanations of the commands and “time slots,” is covered in the 1-WIRE BUS SYSTEM section of this datasheet。 Another feature of the DS18B20 is the ability to operate without an external power supply. Power
13、 is instead supplied through the 1-Wire pullup resistor via the DQ pin when the bus is high. The high bus signal also charges an internal capacitor (CPP), which then supplies power to the device when the bus is low. This method of deriving power from the 1-Wire bus is referred to as “parasite power.
14、” As an alternative, the DS18B20 may also be powered by an external supply on VDD。 四 . OPERATION MEASURING TEMPERATURE The core functionality of the DS18B20 is its direct-to-digital temperature sensor. The resolution of the temperature sensor is user-configurable to 9, 10, 11, or 12 bits, correspond
15、ing to increments of 0.5 C, 0.25 C, 0.125 C, and 0.0625 C, respectively. The default resolution at power-up is 12-bit. The DS18B20 powers-up in a low-power idle state； to initiate a temperature measurement and A-to-D conversion, the master must issue a Convert T 44h command. Following the conversion
16、, the resulting thermal data is stored in the 2-byte temperature register in the scratchpad memory and the DS18B20 returns to its idle state. If the DS18B20 is powered by an external supply, the master can issue “read time slots” (see the 1-WIRE BUS SYSTEM section) after the Convert T command and th
17、e DS18B20 will respond by transmitting 0 while the temperature conversion is in progress and 1 when the conversion is done. If the DS18B20 is powered with parasite power, this notification technique cannot be used since the bus must be pulled high by a strong pullup during the entire temperature con
18、version. The bus requirements for parasite power are explained in detail in the POWERING THE DS18B20 section of this datasheet。 The DS18B20 output temperature data is calibrated in degrees centigrade； for Fahrenheit applications, a lookup table or conversion routine must be used. The temperature dat
19、a is stored as a 16-bit sign-extended twos complement number in the temperature register (see Figure 2). The sign bits (S) indicate if the temperature is positive or negative: for positive numbers S = 0 and for negative numbers S = 1. If the DS18B20 is configured for 12-bit resolution, all bits in t
20、he temperature register will contain valid data. For 11-bit resolution, bit 0 is undefined. For 10-bit resolution, bits 1 and 0 are undefined, and for 9-bit resolution bits 2, 1 and 0 are undefined. Table 2 gives examples of digital output data and the corresponding temperature reading for 12-bit resolution conversions。 五 . OPERATION ALARM SIGNALING After the DS18B20 performs a temperature conversion, the temperature value is compared to the user-defined twos complement alarm trigger values stored in the 1-byte TH and
