【正文】 e match ROM mand followed by a 64bit ROM code sequence allows 外文翻譯（原文） 9 the bus master to address a specific slave device on a multidrop or singledrop bus. Only the slave that exactly matches the 64bit ROM code sequence will respond to the function mand issued by the master。C, and 176。C to +85176。F to +257176。 Interface Requires Only One Port Pin for Communication ? Each Device has a Unique 64Bit Serial Code Stored in an OnBoard ROM ? Multidrop Capability Simplifies Distributed TemperatureSensing Applications ? Requires No External Components 外文翻譯（原文） 2 ? Can Be Powered from Data Line。 176。外文翻譯（原文） 1 中英文資料外文翻譯文獻(xiàn) The introduction to The DS18B20 1. DESCRIPTION The DS18B20 digital thermometer provides 9bit to 12bit Celsius temperature measurements and has an alarm function with nonvolatile user programmable upper and lower trigger points. The DS18B20 municates over a 1Wire bus that by definition requires only one data line for munication with a central microprocessor. It has an operating temperature range of 55176。C over the range of 10176。 Power Supply Range is to ? Measures Temperatures from 55176。F) ? 177。C ? Thermometer Resolution is User Selectable from 9 to 12 Bits ? Converts Temperature to 12Bit Digital Word in 750ms (Max) ? UserDefinable Nonvolatile (NV) Alarm Settings ? Alarm Search Command Identifies and Addresses Devices Whose Temperature is Outside Programmed Limits ? Software Compatible with the DS1822 ? Applications Include Thermostatic Controls, Industrial Systems, Consumer Products, Thermometers, or Any Thermally Sensitive System Figure 1 shows a block diagram of the DS18B20, and pin descriptions are given in the Pin Description table. The 64bit ROM stores the device’s unique serial code. The scratchpad memory contains the 2byte temperature register that stores the digital output from the temperature sensor. In addition, the scratchpad provides access to the 1byte upper and lower alarm trigger registers (TH and TL) and the 1byte configuration register. The configuration register allows the user to set the resolution of the temperature todigital 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 Maxim’s exclusive 1Wire bus protocol that implements bus munication using one control signal. The control line requires a weak pull up resistor since all devices are linked to the bus via a 3state or opendrain 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 using each device’s unique 64bit code. Because each device has a unique code, the number of devices that can be addressed on one DS18B20 bus is virtually unlimited. The 1Wire bus protocol, 外文翻譯（原文） 3 including detailed explanations of the mands and “ time slots,‖ is covered in the 1Wire Bus System section. Another feature of the DS18B20 is the ability to operate without an external power supply. Power is instead supplied through the 1Wire 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 bus is low. This method of deriving power from the 1Wire bus is referred to as ―parasite power.‖ As an alternative, the DS18B20 may also be powered by an external supply on VDD. 6 4 B I T R O MA N D1 W I R E P O R TM E M O R Y C O N T R O LL O G I CS C R A T C H P A D T E M P E R A T U R E S E N S O R A L A R M H I G H T R I G G E R ( T H ) A L A R M L O W T R I G G E R ( T L ) C O N F I G U R A T I O N R E G I S T E R 8 B I T C R C G E N E R A T O R P O W E R S U P P L Y S E N S E I N T E R N A L V d dP A R A S I T E P O W E R C I R C U I T C p pV p u4 . 7 KD QG N DV d d Figure Block Diagram —MEASURING TEMPERATUR The core functionality of the DS18B20 is its directtodigital temperature sensor. The resolution of the temperature sensor is userconfigurable to 9, 10, 11, or 12 bits, corresponding to increments of 176。C, respectively. The default resolution at powerup is 12bit. The DS18B20 powers up in a lowpower idle state. To initiate a temperature measurement and AtoD conversion, the master must issue a Convert T [44h] mand. Following the conversion, the resulting thermal data is stored in the 2byte temperature register in the scratchpad memory and the DS18B20 returns to its idle state. If the DS18B20 is powered by an external supply, the master can issue ―read time slots‖ (see the 1Wire Bus System section) after the Convert T mand and the DS18B20 will respond by transmitting 0 while 外文翻譯（原文） 4 the temperature conversion is in progress and 1 when the conversion is done. If the DS18B20 is powered with parasite power, this notification 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。 all other slaves on the bus will wait for a reset pulse. ROM [CCh] The master can use this mand to address all devices on the bus simultaneously without sending out any ROM code information. For example, the master can make all DS18B20s on the bus perform simultaneous temperature conversions by issuing a Skip ROM mand followed by a Convert T [44h] mand. Note that the Read Scratchpad [BEh] mand can follow the Skip ROM mand only if there is a single slave device on the bus. In this case, time is saved by allowing the master to read from the slave without sending the device’s 64bit ROM code. A Skip ROM mand followed by a Read Scratchpad mand will cause a data collisio