US Patent 7133936 Ring network and data transmitter

A ring-shaped network quickly performs initialization even when a plurality of data transmission apparatuses are connected thereto. Each data transmission apparatus outputs received data to a device connected thereto while performing establishment of clock synchronization based on the received data, and when synchronization is established, it resends the received data. Further, when synchronization of the connected device is established, it sends data supplied from the connected device. Further, a master data transmission apparatus outputs data at turn-on of power or immediately after reset, and a next-stage slave data transmission apparatus receives the data to establish synchronization, and resends the received data when synchronization is established. Thus, synchronization of all the data transmission apparatuses is established while making a round of this data, and then synchronization of devices connected to the respective data transmission apparatuses is established.