DS18B20数字式温度传感器毕业论文中英文资料外文翻译文献.doc
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1、外文翻译(原文) 中英文资料外文翻译文献 The introduction to The DS18B201. DESCRIPTION The DS18B20 digital thermometer provides 9-bit to 12-bit Celsius temperature 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
2、 definition requires only one data line for communication with a central microprocessor. It has an operating temperature range of -55C to +125C and is accurate to 0.5C over the range of -10C to +85C. In addition, the DS18B20 can derive power directly from the data line (“parasite power”), eliminatin
3、g the need for an external power supply. Each DS18B20 has a unique 64-bit serial code, which allows multiple DS18B20s to function on the same 1-Wire bus. Thus, it is simple to use one microprocessor to control many DS18B20s distributed over a large area. Applications that can benefit from this featu
4、re include HVAC environmental controls, temperature monitoring systems inside buildings, equipment, or machinery, and process monitoring and control systems.2.FEATURESl Unique 1-Wire Interface Requires Only One Port Pin for Communicationl Each Device has a Unique 64-Bit Serial Code Stored in an On-B
5、oard ROMl Multi-drop Capability Simplifies Distributed Temperature-Sensing Applicationsl Requires No External Componentsl Can Be Powered from Data Line; Power Supply Range is 3.0V to 5.5V l Measures Temperatures from -55C to +125C (-67F to +257F)l 0.5C Accuracy from -10C to +85Cl Thermometer Resolut
6、ion is User Selectable from 9 to 12 Bitsl Converts Temperature to 12-Bit Digital Word in 750ms (Max)l User-Definable Nonvolatile (NV) Alarm Settingsl Alarm Search Command Identifies and Addresses Devices Whose Temperature is Outside Programmed Limitsl Software Compatible with the DS1822l Application
7、s Include Thermostatic Controls, Industrial Systems, Consumer Products, Thermometers, or Any Thermally Sensitive System3.OVERVIEWFigure 1 shows a block diagram of the DS18B20, and pin descriptions are given in the Pin Description table. The 64-bit ROM stores the devices unique serial code. The scrat
8、chpad memory contains the 2-byte temperature register that stores the digital output from the temperature 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
9、 user to set the resolution of the temperature to-digital conversion to 9, 10, 11, or 12 bits. The TH, TL, and configuration registers are nonvolatile (EEPROM), so they will retain data when the device is powered down.The DS18B20 uses Maxims exclusive 1-Wire bus protocol that implements bus communic
10、ation using one control signal. The control line requires a weak pull up resistor since all devices are linked 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 u
11、sing each devices unique 64-bit code. Because each device has a unique code, the number of devices that can be addressed on one DS18B20 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.A
12、nother feature of the DS18B20 is the ability to operate without an external power supply. Power is instead supplied through the 1-Wire pull up 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
13、bus is low. This method of deriving power from the 1-Wire bus is referred to as “parasite power.” As an alternative, the DS18B20 may also be powered by an external supply on VDD. Figure 1.DS18B20 Block Diagram4.OPERATIONMEASURING TEMPERATURThe core functionality of the DS18B20 is its direct-to-digit
14、al temperature sensor. The resolution of the temperature sensor is user-configurable to 9, 10, 11, or 12 bits, corresponding to increments of 0.5C, 0.25C, 0.125C, and 0.0625C, respectively. The default resolution at power-up is 12-bit. The DS18B20 powers up in a low-power idle state. To initiate a t
15、emperature measurement and A-to-D conversion, the master must issue a Convert T 44h command. Following the conversion, 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
16、supply, the master can issue “read time slots” (see the 1-Wire Bus System section) after the Convert T command and the 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 notific
17、ation technique cannot be used since the bus must be pulled high by a strong pull up during the entire temperature conversion. The DS18B20 output temperature data is calibrated in degrees Celsius; for Fahrenheit applications, a lookup table or conversion routine must be used. The temperature data is
18、 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 the t
19、emperature 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 1 gives examples of digital output data and the corresponding temperature reading for 12-bit resol
20、ution conversions. bit7 bit6 bit5 bit4 bit3 bit2 bit1 bit0LS Byte232221202-12-22-32-4 bit15 bit14 bit13 bit12 bit11 bit10 bit9 bit8MS ByteSSSSS262524Figure 2.Temperature Register FormatTEMPERATURE DIGITAL OUTPUT (BINARY) DIGITAL OUTPUT (HEX) +1250000 0111 1101 000007D0H+25.06250000 0001 1001 0001019
21、1H00000 0000 0000 00000000H-25.06251111 1110 0110 1111FE6FH-551111 1100 1001 0000FC90HTable 1.Temperature/Data Relationship5.64-BIT LASERED ROM CODEEach DS18B20 contains a unique 64bit code (see Figure 3) stored in ROM. The least significant 8 bits of the ROM code contain the DS18B20s 1-Wire family
22、code: 28h. The next 48 bits contain a unique serial number. The most significant 8 bits contain a cyclic redundancy check (CRC) byte that is calculated from the first 56 bits of the ROM code. The 64-bit ROM code and associated ROM function control logic allow the DS18B20 to operate as a 1-Wire devic
23、e using the protocol detailed in the 1-Wire Bus System section.8-BIT CRC48-BIT SERIAL NUMBER8-BIT FAMILY CODE MSB LSB MSB LSB MSBFigure 3.64-Bit Lasered ROM Code6.MEMORYThe DS18B20s memory is organized as shown in Figure 4. The memory consists of an SRAM scratchpad with nonvolatile EEPROM storage fo
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