Patent ID: 7161903

Claim:
A network system for carrying out communication between a control station and a plurality of devices connected to a network and controlled by the control station, wherein the communication includes data communication which requires real-time attributes and message communication which does not require real-time attributes, comprising: a plurality of transmission queues for temporarily storing transmission data provided in the control station, wherein the data communication includes a first data communication in which data is transmitted from the control station to the devices and data in response to this transmission is transmitted from the devices to the control station, and a second data communication in which data is transmitted from the control station at a prescribed timing, the second data communication transmitting data of a higher priority than the first data communication, wherein one of the queues holds transmission data for the second data communication; wherein after the first data communication is carried out in accordance with a predetermined cycle time, an appropriate switching between the message communication and the second data communication is carried out in the remaining time of the cycle time to complete one cycle, whereafter the cycle is repeatedly carried out.