| 摘要 |
PURPOSE: To eliminate time distortion of a sampling period at the time of switchover by a method wherein a temporary main station substituted due to occurrence of a fault of a transmission line for the former main station which synchronizes sampling of all subordinate stations before occurrence of the fault controls the timing of transmission of frame data so as not to disturb the previous sampling time. CONSTITUTION: A frame generating part 1 generates a frame after a prescribed time Ts from a sampling synchronous timing. The time Ts is determined by subtracting a transmission line delay time Tdn /2 from a sampling period T and set in a frame delivery delay time setting part 3. During initialization of a main station, a free-running sampling period T is generated 4. CPU 2 executes a synchronization processing by the free-running period T and makes input to a synchronous timing generating part 5. Making a switching part 6 conduct switchover from the generating part 4 to 5, the CPU 2 sets 3 a delay and the frame data are transmitted downstream by the frame generating part 1. Although the CPU 2 of a subordinate station becoming a temporary main station due to a fault of a transmission line first executes processing by the free-running period T, it makes the frame data be transmitted downstream when a delay time of forward and backward transmission of the transmission line is determined. According to this constitution, synchronization distortion is prevented. |
