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參數(shù)資料
| 型號： | DS18B20P |
| 廠商： | DALLAS SEMICONDUCTOR |
| 元件分類： | Switch/Digital Output Temperature Sensor |
| 英文描述： | DIGITAL TEMP SENSOR-SERIAL, 12BIT(s), 0.50Cel, RECTANGULAR, SURFACE MOUNT |
| 封裝： | TSOC-6 |
| 文件頁數(shù)： | 23/26頁 |
| 文件大小： | 387K |
| 代理商： | DS18B20P |
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DS18B20
6 of 26
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
8 + X5 + X4 + 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 eighth bit of the family code has been entered, then the serial number
is entered. After the 48
th 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
相關(guān)PDF資料 |
PDF描述 |
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| DS18B20X | DIGITAL TEMP SENSOR-SERIAL, 12BIT(s), 2Cel, RECTANGULAR, SURFACE MOUNT |
| DS18B20Z | DIGITAL TEMP SENSOR-SERIAL, 12BIT(s), 0.50Cel, RECTANGULAR, SURFACE MOUNT |
| DS18B20 | DIGITAL TEMP SENSOR-SERIAL, 12BIT(s), 0.50Cel, RECTANGULAR, THROUGH HOLE MOUNT |
| DS18B20U+T&R | DIGITAL TEMP SENSOR-SERIAL, 12BIT(s), 0.50Cel, SQUARE, SURFACE MOUNT |
| DS18B20-SL+T&R | DIGITAL TEMP SENSOR-SERIAL, 12BIT(s), 0.50Cel, RECTANGULAR, THROUGH HOLE MOUNT |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| DS18B20-PAR | 功能描述:板上安裝溫度傳感器 RoHS:否 制造商:Omron Electronics 輸出類型:Digital 配置: 準確性:+/- 1.5 C, +/- 3 C 溫度閾值: 數(shù)字輸出 - 總線接口:2-Wire, I2C, SMBus 電源電壓-最大:5.5 V 電源電壓-最小:4.5 V 最大工作溫度:+ 50 C 最小工作溫度:0 C 關(guān)閉: 安裝風(fēng)格: 封裝 / 箱體: 設(shè)備功能:Temperature and Humidity Sensor |
| DS18B20-PAR/T&R | 功能描述:板上安裝溫度傳感器 RoHS:否 制造商:Omron Electronics 輸出類型:Digital 配置: 準確性:+/- 1.5 C, +/- 3 C 溫度閾值: 數(shù)字輸出 - 總線接口:2-Wire, I2C, SMBus 電源電壓-最大:5.5 V 電源電壓-最小:4.5 V 最大工作溫度:+ 50 C 最小工作溫度:0 C 關(guān)閉: 安裝風(fēng)格: 封裝 / 箱體: 設(shè)備功能:Temperature and Humidity Sensor |
| DS18B20-PAR_07 | 制造商:MAXIM 制造商全稱:Maxim Integrated Products 功能描述:1-Wire Parasite-Power Digital Thermometer |
| DS18B20-PAR+T&R | 制造商:Maxim Integrated Products 功能描述: 制造商:Maxim Integrated Products 功能描述:TEMP SENSOR DGTL 1-WIRE 3PIN TO-92 - Tape and Reel 制造商:Maxim Integrated Products 功能描述:IC THERM MICROLAN PROG-RES TO-92 制造商:Maxim Integrated Products 功能描述:Board Mount Temperature Sensors Prgmble Resolution 1-Wire Parasite Pwr |
| DS18B20-PAR+T&R | 功能描述:板上安裝溫度傳感器 Prgmble Resolution 1-Wire Parasite Pwr RoHS:否 制造商:Omron Electronics 輸出類型:Digital 配置: 準確性:+/- 1.5 C, +/- 3 C 溫度閾值: 數(shù)字輸出 - 總線接口:2-Wire, I2C, SMBus 電源電壓-最大:5.5 V 電源電壓-最小:4.5 V 最大工作溫度:+ 50 C 最小工作溫度:0 C 關(guān)閉: 安裝風(fēng)格: 封裝 / 箱體: 設(shè)備功能:Temperature and Humidity Sensor |
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