Datasheet

Jon Waddington
28
480µs. This is the Reset pulse. The Propeller then releases the bus to be pulled high by
the 4.7kΩ resistor. The DS18B20 responds to this with a Presence pulse by waiting 15 to
60µs for the bus to go high and then pulling it low for between 60 and 240 µs. These
pulses are shown in figure 3.5.2.1 [34].
The read and write slots are issued by the Propeller and allow for one bit to be
transmitted. By issuing a write slot, the Propeller is able to write data to the DS18B20.
By issuing a Read time slot, the Propeller is able to read data from the DS18B20.
Each Read or Write time slot is initiated by the Propeller pulling the 1 -Wire bus down. To
write ‘0’, the bus is pulled down and remains pulled down for a minimum of 60 µs. To
write ‘1’, the bus is pulled low by the Propeller and released within 15µs to be pulled up
by the 4.7kΩ resistor [34]. This is shown in figure 3.5.2.2.
Figure 3.5.2.1. Diagram of the 1-Wire Reset and Presence Pulses
Figure 3.5.2.2 . Diagram of the Write and Read Time Slots