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参数资料
| 型号： | DS18B20-PAR/T&R |
| 厂商： | MAXIM INTEGRATED PRODUCTS INC |
| 元件分类： | Switch/Digital Output Temperature Sensor |
| 英文描述： | DIGITAL TEMP SENSOR-SERIAL, 12BIT(s), 0.50Cel, ROUND, THROUGH HOLE MOUNT |
| 封装： | TO-92, 3 PIN |
| 文件页数： | 17/19页 |
| 文件大小： | 203K |
| 代理商： | DS18B20-PAR/T&R |
DS18B20-PAR
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and then compare this value to either the ROM code CRC (for ROM reads) or to the scratchpad CRC (for
scratchpad reads). If the calculated CRC matches the read CRC, the data has been received error free. The
comparison of CRC values and the decision to continue with an operation are determined entirely by the
bus master. There is no circuitry inside the DS18B20-PAR that prevents a command sequence from
proceeding if the DS18B20-PAR CRC (ROM or scratchpad) does not match the value generated by the
bus master.
The equivalent polynomial function of the CRC (ROM or scratchpad) is: CRC = X
8 + X5 + X4 + 1
The bus master can re-calculate the CRC and compare it to the CRC values from the DS18B20-PAR
using the polynomial generator shown in Figure 8. This circuit consists of a shift register and XOR gates,
and the shift register bits are initialized to 0. Starting with the least significant bit of the ROM code or the
least significant bit of byte 0 in the scratchpad, one bit at a time should shifted into the shift register.
After shifting in the 56
th bit from the ROM or the most significant bit of byte 7 from the scratchpad, the
polynomial generator will contain the re-calculated CRC. Next, the 8-bit ROM code or scratchpad CRC
from the DS18B20-PAR must be shifted into the circuit. At this point, if the re-calculated CRC was
correct, the shift register will contain all 0s. 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.”
CRC GENERATOR Figure 8
1-WIRE BUS SYSTEM
The 1-Wire bus system uses a single bus master to control one or more slave devices. The DS18B20-
PAR is always a slave. When there is only one slave on the bus, the system is referred to as a “single-
drop” system; the system is “multi-drop” if there are multiple slaves on the bus.
All data and commands are transmitted least significant bit first over the 1-Wire bus.
The following discussion of the 1-Wire bus system is broken down into three topics: hardware
configuration, transaction sequence, and 1-Wire signaling (signal types and timing).
HARDWARE CONFIGURATION
The 1-Wire bus has by definition only a single data line. Each device (master or slave) interfaces to the
data line via an open drain or 3–state port. This allows each device to “release” the data line when the
device is not transmitting data so the bus is available for use by another device. The 1-Wire port of the
DS18B20-PAR (the DQ pin) is open drain with an internal circuit equivalent to that shown in Figure 9.
The 1-Wire bus requires an external pullup resistor of approximately 5 k
Ω; thus, the idle state for the 1-
Wire bus is high. If for any reason a transaction needs to be suspended, the bus MUST be left in the idle
state if the transaction is to resume. Infinite recovery time can occur between bits so long as the 1-Wire
bus is in the inactive (high) state during the recovery period. If the bus is held low for more than 480
μs,
all components on the bus will be reset. In addition, to assure that the DS18B20-PAR has sufficient
supply current during temperature conversions, it is necessary to provide a strong pullup (such as a
MOSFET) on the 1-Wire bus whenever temperature conversions or EEPROM writes are taking place (as
described in the PARASITE POWER section).
(MSB)
(LSB)
XOR
INPUT
相关PDF资料 |
PDF描述 |
|---|---|
| DS18B20-PAR | DIGITAL TEMP SENSOR-SERIAL, 12BIT(s), 0.50Cel, ROUND, THROUGH HOLE MOUNT |
| DS18B20P | DIGITAL TEMP SENSOR-SERIAL, 12BIT(s), 0.50Cel, RECTANGULAR, SURFACE MOUNT |
| 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 |
相关代理商/技术参数 |
参数描述 |
|---|---|
| DS18B20-SL | 制造商:DALLAS 制造商全称:Dallas Semiconductor 功能描述:Programmable Resolution 1-Wire Digital Thermometer |
| DS18B20-SL/T&R | 功能描述:板上安装温度传感器 RoHS:否 制造商:Omron Electronics 输出类型:Digital 配置: 准确性:+/- 1.5 C, +/- 3 C 温度阈值: 数字输出 - 总线接口:2-Wire, I2C, SMBus 电源电压-最大:5.5 V 电源电压-最小:4.5 V 最大工作温度:+ 50 C 最小工作温度:0 C 关闭: 安装风格: 封装 / 箱体: 设备功能:Temperature and Humidity Sensor |
| DS18B20-SL+T&R | 制造商:Maxim Integrated Products 功能描述:TEMP SENSOR DGTL SERL (1-WIRE) - 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-SL+T&R | 功能描述:板上安装温度传感器 Prgmble Resolution 1-Wire Parasite Pwr RoHS:否 制造商:Omron Electronics 输出类型:Digital 配置: 准确性:+/- 1.5 C, +/- 3 C 温度阈值: 数字输出 - 总线接口:2-Wire, I2C, SMBus 电源电压-最大:5.5 V 电源电压-最小:4.5 V 最大工作温度:+ 50 C 最小工作温度:0 C 关闭: 安装风格: 封装 / 箱体: 设备功能:Temperature and Humidity Sensor |
| DS18B20U | 功能描述:板上安装温度传感器 RoHS:否 制造商:Omron Electronics 输出类型:Digital 配置: 准确性:+/- 1.5 C, +/- 3 C 温度阈值: 数字输出 - 总线接口:2-Wire, I2C, SMBus 电源电压-最大:5.5 V 电源电压-最小:4.5 V 最大工作温度:+ 50 C 最小工作温度:0 C 关闭: 安装风格: 封装 / 箱体: 设备功能:Temperature and Humidity Sensor |
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