US Patent 7885196 Loop communication system and communication device

A loop communication system includes a plurality of communication devices, each of which holds an identification data assigned to the communication device, and has a single port used for transmission and reception of a data packet for a transmission data, and which are connected by using the ports to constitute a port synchronization type network of a loop structure. The data packet from each of the plurality of communication devices is transferred on the network of the loop structure in one direction.