Periodic control synchronous system

A periodic control synchronizing system for synchronizing periodic control between a controller connected in a network and devices connected to said network, wherein

• said controller includes
• a first global timer;
• a control period timer which generates a control period for periodic control of said controller;
• a time stamp providing unit which provides a periodic transfer packet with a time stamp showing a synchronizing timing synchronizing time of the control period, indicated by said control period timer, using global time indicated by said first global timer;
• and
• a transmitting unit which transmits the periodic transfer packet provided with the time stamp to said devices, and
• each of said devices includes
• a second global timer controlled through said network;
• a periodic control unit which synchronizes operation period of said device with the control period using the synchronizing time of the periodic control, indicated by the time stamp of the periodic transfer packet transmitted by said transmitting unit, and global time indicated by said second global timer;
• an operation period timer which generates a synchronizing time for synchronizing periodic control of said device;
• and
• a comparing unit which
• compares the synchronizing time of the periodic control, indicated by the time stamp of the periodic transfer packet transmitted by said transmitting unit, and the global time indicated by said second global timer,
• determines a time difference between the synchronizing time of the periodic control, indicated by the time stamp, and the global time indicated by said second global timer, and
• determines a timer correction value of said operation control period timer based on the time difference, wherein said operation period timer is corrected by said comparing unit, based on the timer correction value, at the synchronizing time.