Datasheet

Jon Waddington
61
The propeller waits until the temperature conversion is complete by issuing read time
slots. The DS18B20 responds to this by transmitting ‘0’ until the conversion is complete
and it will transmit a ‘1’. The Propeller then transmits the Skip ROM command aga in,
followed by the Read Scratchpad command. This transmission can be seen in figure
4.4.1.2.
When the DS18B20 receives the Read Scratchpad command, it begins transmitting the
contents of the Scratchpad until a reset pulse is transmitted by the Propeller. The
temperature value is contained in the first two bytes of the Scratchpad. Figure 4.4.1.3
shows the transmission of the 8 least significant bits of the temperature.
Figure 4.4.1.2. Waveform of the Skip ROM and Read Scratchpad commands
0xCC
0xBE
LSB MSB
LSB MSB
0
1
1
1
1
1
0
0
0
1
1
1
1
1
0
0
Figure 4.4.1.3. Waveform of the 8 least significant bits of the Scratchpad
1
1
0
1
0
0
0
0
LSB MSB
0xB0