DS18B20中文手册：1-Wire温度传感器详解

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DS18B20中文芯片手册是一份详细介绍美国Maxim Integrated公司生产的DS18B20数字温度传感器的手册，该芯片以其独特的1-Wire接口设计而闻名。1-Wire接口仅需一个端口引脚进行通信，大大简化了分布式温度传感应用的设计。这款芯片无需外部组件，能够通过数据线供电，工作电压范围广泛，从3.0V到5.5V，即使在零备用电源条件下也能正常运行。 DS18B20适用于-55°C至+125°C（-67°F至+257°F）的温度测量，具有±0.5°C的高精度，在-10°C至+85°C的范围内，其分辨率可编程调整，从9位到12位不等。这意味着用户可以根据需要选择不同的精度级别，以满足特定的应用需求。在数据处理方面，12位温度转换成数字信号的时间最快可达750毫秒。更值得一提的是，DS18B20支持用户自定义的、非易失性的温度报警设置。通过执行报警搜索命令，可以检测并定位出当前温度超出预设阈值的设备，这对于环境监控、工业系统控制、家用电器以及对温度敏感的任何应用场景都非常实用。例如，在家庭暖通空调、数据中心或食品储存设备中，它可以确保精确的温度控制并及时发出警报。此外，芯片的引脚分配简单明了：GND代表接地，用于电路的电气连接；DQ是数据输入/输出引脚，用于与控制器进行双向通信；VDD则是电源引脚，提供芯片所需的电力；NC表示无连接，可以留给用户根据需要进行接线。 DS18B20数字温度传感器凭借其紧凑的接口、精确的测量能力、灵活的配置选项以及报警功能，成为现代电子产品中不可或缺的温度感知元件，广泛应用于各种工业和消费级产品中，提升了系统的可靠性和效率。掌握并理解这份手册的内容，对于在实际项目中有效运用和维护这种温度传感器至关重要。

DS18B20

6 of 27

64-BIT LASERED ROM

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 CRC 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 functions required to control sections of the DS18B20 are not accessible until the ROM

function protocol has been satisfied. This protocol is described in the ROM function protocol flowchart

(Figure 5). The 1-Wire bus 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. After a ROM function

sequence has been successfully executed, the functions specific to the DS18B20 are accessible and the

bus master may then provide one of the six memory and control function commands.

CRC GENERATION

The DS18B20 has an 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 ROM data has been received error-free by the bus master. The

equivalent polynomial function of this CRC is:

CRC = X

+ X

+ 1

The DS18B20 also generates an 8-bit CRC value 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 calculate 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 within the DS18B20

(which is read as a ninth byte when the scratchpad is read). The comparison of CRC values and decision

to continue with an operation are determined entirely by the bus master. There is no circuitry inside the

DS18B20 that prevents a command sequence from proceeding if the CRC stored in or calculated by the

DS18B20 does not match the value generated by the bus master.

The 1-Wire CRC can be generated using a polynomial generator consisting of a shift register and XOR

gates as shown in Figure 6. Additional information about the Dallas 1-Wire Cyclic Redundancy Check is

available in Application Note 27 entitled “Understanding and Using Cyclic Redundancy Checks with

Dallas Semiconductor Touch Memory Products.”

The shift register bits are initialized to 0. Then starting with the least significant bit of the family code,

1 bit at a time is shifted in. After the 8th bit of the family code has been entered, then the serial number is

entered. After the 48

bit of 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 0s.

64-BIT LASERED ROM Figure 4

8-BIT CRC CODE 48-BIT SERIAL NUMBER

8-BIT FAMILY CODE

(28h)

MSB LSB MSB LSB MSB LSB

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