【正文】 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 parison of CRC values and the decision to continue with an operation are determined entirely by the bus is no circuitry inside the DS18B20 that prevents a mand sequence from proceeding if the DS18B20 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: The bus master can recalculate the CRC and pare it to the CRC values from the DS18B20 using the polynomial generator shown in Figure 9. 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 56thbit from the ROM or the most significant bit of byte 7 from the scratchpad, the polynomial generator will contain the recalculated CRC. Next, the 8bit ROM code or scratchpad CRC from the DS18B20 must be shifted into the circuit. At this point, if the recalculated CRC was correct, the shift register will contain all 0s. Additional information about the Dallas 1Wire cyclic redundancy check is available in Application Note 27: Understanding and Using Cyclic Redundancy Checks with Dallas Semiconductor Touch Memory Products. DS18B20 單線溫度傳感器 一． 特征： ● 獨特的單線接口，只需 1 個接口引腳即可通信 ● 每個設備都有一個唯一的 64位串行代碼存儲在光盤片上 ● 多點能力使分布式溫度檢測應用得以簡化 ● 不需要外部部件 ● 可以從數(shù)據(jù)線供電 ， 電源電壓范圍為 ● 測量范圍從 55 176。 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 2 gives examples of digital output data and the corresponding temperature reading for 12bit resolution conversions。Cand is accurate to C over the range of –10176。 本科生畢業(yè)設計（論文）外文翻譯 譯文題目： DS18B20 單線溫度傳感器 外文題目： DS18B20 Single wire temperature sensor 學 院： 信息科學與工程學院 專業(yè)班級： 電子信息工程 0804 班 學生姓名： 指導教師： DS18B20 Single wire temperature sensor 一 . FEATURES ● Unique 1Wireinterface requires only one port pin for munication ● Each device has a unique 64bit serial code stored in an onboard ROM ● Multidrop capability simplifies distributed temperature sensing applications ● Requires no external ponents ● Can be powered from data line. Power supply range is to ● Measures temperatures from –55176。C to +125176。 The DS18B20 output temperature data is calibrated in degrees centigrade。 at powerup the EEPROM data is reloaded into the corresponding scratchpad locations. Data can also be reloaded from EEPROM to the scratchpad at any time using the Recall E2[B8h] mand. The master can issue read time slots following the Recall E2mand and the DS18B20 will indicate the status of the recall by transmitting 0 while the recall is in progress and 1 when the recall is done. 十 . CONFIGURATION REGISTER Byte 4 of the scratchpad memory contains the configuration register, which is anized as illustrated in Figure 8. The user can set the conversion resolution of the DS18B20 using the R0 and R1 bits in this register as shown in Table 3. The powerup default of these bits is R0 = 1 and R1 = 1 (12bit resolution). Note that there is a direct tradeoff between resolution and conversion time. Bit 7 and bits 0 to 4 in the configuration register are reserved for internal use by the device and cannot be overwritten。信息單線接口送入 DS1820 或從 DS1820 送出，因此按照定義只需要一條數(shù)據(jù)線（和地線）與中央微處理器進行通信。 每個 DS18B20 的有一個唯一的 64 位序列碼，它允許多個 DS18B20s的功能在同一 1巴士線。 該 DS18B20使用 Dallas的單總線協(xié)議，總線之間的通信用一個控制信號就可以實現(xiàn)。這種從但總線提供動力的方法被稱為“寄生電源“。 其中傳感器默認為 12位。溫度數(shù)據(jù)在溫度寄存器存儲為一個 16位符號擴展 位和 2位的補碼 。符號位（ S） 表示溫度值的正負 ： S = 0時為正值， S = 1為 負 值 。如果報警的情況存在 ， TH和 TL設置已 經(jīng)改變了，另一個溫度轉換應該 去 驗證報警條件 。這個電流會導致 無法 接受 的電壓下降，