2英语温度传感器2..docVIP

DS18B20 Programmable Resolution 1-Wire Digital Thermometer 1、DS18B20 FEATURES （1）Unique 1-Wire interface requires only one Port pin for communication, requires no external components （2）Each device has a unique 64-bit serial code stored in an onboard ROM （3）Can be powered form data line .Power supply range is 3.0Vto 5.5V （4）Measures temperatures form -55℃ to +125℃ , ±0.5℃ accuracy from -10℃ to +85℃ （5）Thermometer resolution is user-selected from 9 to 12 bits （6）Converts temperature to 12-bit digital word in 750ms (max) （7）Alarm search command identifies and addresses devices whose temperature is outside of programmed limits (temperature alarm condition) （8） Available in 8-pin SOIC, and 3-bin TO -92 packages 2、DS18B20 BLOCK DIAFRAM Figure 1 shows a block diagram of the DS18B20, The 64-bite ROM stores the device’s serial code. The scratchpad memory contains the 2-byte temperature egister that stores the digital output from the temperature sensor. In addition, the scratchpad provides access to the 1-byte upper and lower alarm trigger register (TH and TL), and the 1-byte configuratuion 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 and configuration registers are nonvolatile(EEPROM), so they will retain data when the device is powered down. Figure 1 block diagram of the DS18B20 3、DS18B20 ROM COMMANDS (1) SEARCH ROM [0F0H] When a system is initially powered up, the master must identify the ROM codes of all slave devices on the bus, which allows the master to determine the number of slaves and their device types. The master learns the ROM codes through a process of elimination that requires the master to perform a Search ROM cycle as many times as necessary to identify all of the slave’s 64-bit ROM devices. (2) READ ROM [55H] This command can only be used when there is one slave on the bus. It allows the bus master to read the slave`