The 1-Wire bus protocol, which is utilized by the DS18B20, only needs one control signal for communication. To avoid the bus port being in a 3-state or high-impedance condition, the control signal line needs a wake-up pull-up resistor (the DQ signal line is on the DS18B20). The microcontroller (master device) in this bus system recognizes the bus's devices by their 64-bit serial numbers. A bus may potentially support a limitless number of devices because each one has a distinct serial number.
The DS18B20 does not require an external power source to function. The device is powered when the data line DQ is high. The internal capacitor (Spp) charges when the bus is pulled high, and the capacitor powers the device when the bus is pulled low. "Parasitic power" is the term used to describe this method of 1-Wire bus device powering.
The temperature readings from the DS18B20 temperature sensor are 9-bit (binary), suggesting that the device's temperature data is either sent to the DS18B20 temperature sensor via the single-line interface or that it is sent out from the DS18B20 temperature sensor. As a result, just one line (plus ground) is required to connect the host CPU to the DS18B20 temperature sensor, and the data line itself can act as the sensor's power source in place of an external power source.