A structure and process are provided for using a single wire or data bus to
detect collisions between two communication nodes connected by the single
wire by sensing current changes in the wire, where large current changes
indicate a collision. When a second node wants to obtain control of the
wire on which a first node is transmitting data, the second node transmits
a special data packet to ensure a collision and cause a large current to
flow on the wire. Once a large current is detected in the wire to indicate
a bit difference or collision, the first node stops transmitting and waits
until it receives a synchronization bit pattern, which will indicate that
the special data packet transmitted by the second node has ended. The two
nodes are now synchronized, such that the second node has control of the
wire and can begin transmission of a data packet. In order to indicate a
collision, the large current flow must remain high after a specified time
interval, such as a clock cycle. In the case of a capacitive load, such as
a bus, the time interval is the time needed for the bus to settle.
