Patent ID: 7080175

Claim:
A network system comprising; a single general-purpose serial communication circuit; and a plurality of programmable controllers connected to said general-purpose serial communication circuit, one of said programmable controllers being a parent station, the rest of said programmable controllers being each a child station, each one of said child stations being adapted to transmit a command when a token issued by said parent station is received thereby; wherein, if said command is a link data write command for transmitting link data to said parent station, said parent station stores said link data at a preliminarily specified link data storing area within said parent station and transmits a link data write response whereby the link data of all said child stations are transmitted and when said link data write response from said parent station is received, the child station writes said link data in a preliminary specified link data storing area within said child station; and wherein, if said command is an event data read command for reading out specified data at a specified one of said programmable controllers, said specified one of the programmable controllers transmits a data read response including said specified data, and the child station which received said data read response stores said specified data in a specified area.