US Patent 7317690 Method of constructing network topology and interface circuit

An interface circuit that can disconnect a loop connection among nodes. The interface circuit includes ports, which are connected to bus cables, a state machine and a port controller, which is connected to the ports and the state machine. The state machine determines that a loop connection exists when a process in a predetermined state has been stacked for a predetermined time. When a loop connection exists, the port controller electrically disconnects a port on the loop.