ds1820单总线数字温度计外文翻译(编辑修改稿)

ds1820单总线数字温度计外文翻译(编辑修改稿)内容摘要：

conversions. When using the parasite power mode, the VDD pin must be tied to ground. Another method of supplying current to the DS18B20 is through the use of an external power supply tied to the VDD pin, as shown in Figure 3. The advantage to this is that the strong pull up is not required on the DQ line, and the bus master need not be tied up holding that line high during temperature conversions. This allows other data traffic on the 1Wire bus during the conversion time. In addition, any number of DS18B20s may be placed on the 1Wire bus, and if they all use external power, they may all simultaneously perform temperature conversions by issuing the Skip ROM mand and then issuing the Convert T mand. Note that as long as the external power supply is active, the GND pin may not be floating. sustain munications given the higher leakage currents the DS18B20 exhibits at these temperatures. For applications in which such temperatures are likely, it is strongly remended that VDD be applied to the DS18B20. For situations where the bus master does not know whether the DS18B20s on the bus are parasite powered or supplied with external VDD, a provision is made in the DS18B20 to signal the power supply scheme used. The bus master can determine if any DS18B20 are on the bus which require the strong pull up by sending a Skip ROM protocol, then issuing the read power supply mand. After this mand is issued, the master then issues read time slots. The DS18B20 will send back “0” on the 1Wire bus if it is parasite powered。 it will send back a “1” if it is powered from the VDD pin. If the master receives a “0,” it knows that it must supply the strong pull up on the DQ line during temperature conversions. See “Memory Command 3 Functions” section for more detail on this mand protocol. The DS18B20 has an 8bit CRC stored in the most significant byte of the 64bit ROM. The bus master can pute a CRC value from the first 56bits of the 64bit ROM and pare it to the value stored within the DS18B20 to determine if the ROM data has been received errorfree by the bus master. The equivalent polynomial function of this CRC is: 1458  XXXC RC The DS18B20 also generates an 8bit CRC value using the same polynomial function。