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Once the Slave devices on the bus are synchronized to a known state, the bus Master can start communicating with the Slave devices. This slide shows how the Master writes and reads a logic 1 or 0. The Master initiates a Slave Write 1 command by pulling the line low for a defined duration and then releasing it. The 1-Wire line is returned to the logic high idle state through either an external pull up resistor or integrated line driver. The 1-Wire Slave device starts its internal time base at the falling edge of the Master and samples the line after a maximum of 15µsec. At this time the 1-Wire bus is idling at high again. The Slave devices recognize the logic high bus status as a Write 1 request. The Master initiates a Slave Write 0 command by pulling the line low for a maximum of 60µsec and releasing it. The 1-Wire Slave device starts its internal time base at the falling edge of the Master and samples the line after a maximum of 15µsec. Since the 1-Wire bus is active (low), the Slave device recognizes this as a write 0 request. The Master initiates a Slave Read 1 command by pulling the line low and releasing it. The 1-Wire line is returned to the logic high idle state through either an external pull up resistor or integrated line driver. The Master samples the line after a minimum of 15µsec (tmsr). At this time the 1-Wire bus is idling at high again. The Master recognizes this as a Read 1 request. The Master than initiates a Slave Read 0 command by pulling the line low and releasing it. The 1-Wire Slave device starts its internal time base at the falling edge of the Master and also pulls the line low for at least 15µsec. The Master samples the line at 15µsec (tmsr) and recognizes the active low bus status as a Read 0.
