Data relay device and data relay method used in the device

A data relay device connected to a first communication line through which first data is transmitted/received in accordance with an event trigger type communication protocol and to a second communication line through which second data is transmitted/received in accordance with a time trigger type communication protocol, the data relay device comprising:

• an estimation section which estimates, with reference to a timing at which the first data transmitted from at least one first communication node connected to the first communication line is received, first transmission timings of all the first data transmitted/received through the first communication line;
• a schedule storage section which stores a predetermined schedule in accordance with which the second data is transmitted/received in accordance with the time trigger type communication protocol;
• a determination section which determines a reference timing for the schedule, by calculating stay periods which occur when data is relayed to one of the first communication line and the second communication line, based on the first transmission timings estimated by the estimation section and on the schedule stored in the schedule storage section;
• and
• a synchronization processing section which performs synchronization processing with at least one second communication node connected to the second communication line such that the second data is transmitted/received in accordance with the schedule with reference to the reference timing determined by the determination section.