【正文】 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 Accuracy from 10176。F) ? 177。C (67176。 Power Supply Range is to ? Measures Temperatures from 55176。C. In addition, the DS18B20 can derive power directly from the data line (―parasite power‖), eliminating the need for an external power supply. Each DS18B20 has a unique 64bit serial code, which allows multiple DS18B20s to function on the same 1Wire bus. Thus, it is simple to use one microprocessor to control many DS18B20s distributed over a large area. Applications that can benefit from this feature include HVAC environmental controls, temperature monitoring systems inside buildings, equipment, or machinery, and process monitoring and control systems. ? Unique 1Wire174。C over the range of 10176。C and is accurate to 177。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 to +125176。 176。C to +85176。 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。C to +125176。F to +257176。176。C to +85176。C, 176。C, and 176。 for Fahrenheit applications, a lookup table or conversion routine must be used. The temperature data is stored as a 16bit signextended two’s plement number in the temperature register (see Figure 2). The sign bits (S) indicate if the temperature is positive or negative: for positive numbers S = 0 and for negative numbers S = 1. If the DS18B20 is configured for 12bit resolution, all bits in the temperature register will contain valid data. For 11bit resolution, bit 0 is undefined. For 10bit resolution, bits 1 and 0 are undefined, and for 9bit resolution bits 2, 1, and 0 are undefined. Table 1 gives examples of digital output data and the corresponding temperature reading for 12bit resolution conversions. bit7 bit6 bit5 bit4 bit3 bit2 bit1 bit0 LS Byte 23 22 21 20 21 22 23 24 bit15 bit14 bit13 bit12 bit11 bit10 bit9 bit8 MS Byte S S S S S 26 25 24 Figure Register Format TEMPERATURE DIGITAL OUTPUT (BINARY) DIGITAL OUTPUT (HEX) +125℃ 0000 0111 1101 0000 07D0H +℃ 0000 0001 1001 0001 0191H 0℃ 0000 0000 0000 0000 0000H ℃ 1111 1110 0110 1111 FE6FH 55℃ 1111 1100 1001 0000 FC90H Table LASERED ROM CODE 外文翻譯（原文） 5 Each DS18B20 contains a unique 64–bit code (see Figure 3) stored in ROM. The least significant 8 bits of the ROM code contain the DS18B20’s 1Wire family code: 28h. The next 48 bits contain a unique serial number. The most significant 8 bits contain a cyclic redundancy check (CRC) byte that is calculated from the first 56 bits of the ROM code. The 64bit ROM code and associated ROM function control logic allow the DS18B20 to operate as a 1Wire device using the protocol detailed in the 1Wire Bus System section. 8BIT CRC 48BIT SERIAL NUMBER 8BIT FAMILY CODE MSB LSB MSB LSB MSB Figure Lasered ROM Code The DS18B20’s memory is anized as shown in Figure 4. The memory consists of an SRAM scratchpad with nonvolatile EEPROM storage for the hi gh and low alarm trigger registers (TH and TL) and configuration register. Note that if the DS18B20 alarm function is not used, the TH and TL registers can serve as generalpurpose memory. Byte 0 and byte 1 of the scratchpad contain the LSB and the MSB of the temperature register, respectively. These bytes are readonly. Bytes 2 and 3 provide access to TH and TL registers. Byte 4 contains the configuration register data. Bytes 5, 6