Method and apparatus for implementing an ethernet protocol using three wires

A method of transmitting signals from a digital MAC interface having a transmit data line to a bus having a first bus data line and a second bus data line comprising:

• modulating the first bus data line by holding the first bus data line at a pre-selected potential when the transmit data line is in a first state and allowing the first bus data line to float when the transmit data line is in a second state during an interval when data transmission from the digital MAC interface is enabled;
• and
• modulating the second bus data line by holding the second bus data line at the pre-selected potential when the transmit data line is in the second state and by allowing the second bus data line to float when the transmit data line is in the first state;
• whereby the first bus data line is set to a first logic level while at the same time the second bus data line to is set to a second logic level to transmit a first binary data value, and the first bus data line is set to the second logic level while at the same time the second bus data line is set to the first logic level to transmit a second binary data value.

A method of transmitting signals from a bus having a first bus data line and a second bus data line to a digital MAC interface having a receive data line and a collision line, comprising:

• coupling the first bus data line to a first potential associated with a first logic level while at the same time weakly pulling the second bus data line to a second potential associated with a second logic level, to transmit a first binary data value;
• coupling the second bus data line to the first potential associated with the first logic level while at the same time weakly pulling the first bus data line to the second potential associated with the second logic level, to transmit a second binary data value;
• connecting the first bus data line to the receive data line;
• and
• comparing the state of the first bus data line to the state of the second bus data line and setting the collision line to a pre-selected state associated with a collision being detected if the first bus data line and the second bus data line are both at the first logic level.