Data synchronous transfer system using a fiber distributed data exchange

Abstract

This disclosure is for an improved data synchronous transfer apparatus configured from fiber distributed data interfaces (FDDI) provided with processing functions for synchronous services and asynchronous services are disposed at each node, where these nodes are connected via transfer paths into a ring shape and transfer synchronous data frames. In this system, each node that is a primary stations for synchronizing the set time of the synchronous data frames is provided with a synchronization signal generation circuit that generates a synchronization signal for each set time an external time signal is received from either itself or externally, a token detection circuit in order to detect the receipt of a token that rotates around a transfer path connected in a ring shape, a counter that counts down a predetermined value and that is reset for each generation of the synchronization signal, a frame length conversion circuit, that creates a dummy data frame having a time equivalent in length to a value remaining value on the counter at the time when there is the detection of the receipt of the token that has rotated around the ring-shaped transfer path and has returned, and a transfer control means that synchronizes the transfer start time of the synchronous data frame transferred from the node of the primary station with the set time by the transfer of the dummy data frame prior to the transfer of the synchronous data frame.