Abstract: A synchronous frame reception unit receives a synchronous frame describing a reference value for time synchronization with a management apparatus which is transmitted repeatedly from the management apparatus. A propagation delay computation unit computes, each time when the synchronous frame is received, a propagation delay of the synchronous frame. A propagation delay time period computation unit computes, each time when the propagation delay is computed, a propagation delay time period by adding a target value of a synchronous accuracy to the propagation delay. A propagation delays computation unit operates a logical OR operation of M pieces of propagation delay time periods computed for M pieces of synchronous frames which precede a latest synchronous frame.

Abstract: Even if the propagation time interval of a sync signal is not constant, an accurate correction parameter is calculated, so that a corrected time point synchronized with a main clock device is obtained. A main transmission time point storage part stores respective main transmission time points at which a main device has transmitted a plurality of main sync signals and which are measured using a main clock device. A subordinate reception time point storage part stores respective subordinate reception time points at which a subordinate device has received the plurality of main sync signals and which are measured using a subordinate clock device. A speed ratio calculation part calculates a speed ratio of a ticking time speed of the main clock device to a ticking time speed of the subordinate clock device, based on a main transmission mean time point being a mean of the main transmission time points and a subordinate reception mean time point being a mean of the subordinate reception time points.

Abstract: A peripheral device sends an interrupt generation notification to a bus bridge. The bus bridge receives the interrupt generation notification, transfers the received interrupt generation notification to a CPU, reads an interrupt cause from the peripheral device that has sent the interrupt generation notification, and writes to a memory the interrupt cause that has been read. Upon receiving the interrupt generation notification, the CPU reads the interrupt cause from the memory which allows fast access, and begins interrupt processing corresponding to the interrupt cause. Interrupt processing time up to commencement of the interrupt processing can be reduced.