Patent ID: 7792155
Filing Date: 2010-09-07
Classification: G05B,Y02P

Abstract:
1. A communication system comprising: a master unit which is a programmable controller having a communication function; at least one slave unit which is an I/O terminal unit having a communication function and connected to said master unit by a network; and repeater units inserted on said network between said master unit on their upper side and said at least one slave unit in one or more stages on their lower side; wherein communication frames of various types are transmitted through said network, each of said communication frames containing identification data indicative of the type thereof; wherein a type of a communication frame to be transmitted from said slave unit to said master unit contains identification data indicative of such the type of frame; wherein said repeater units include an upper port connected to the upstream side of said network and a lower port connected to the downstream side of said network, and serve to repeat said communication frame only in a direction from said lower port to said upper port when it is determined that said communication frame received by said repeater units through said upper port or said lower port contains the identification data indicative of the type of frame to be transmitted from said slave unit to said master unit; wherein said master unit serves to transmit a specific communication frame of said communication frames of various types and read out, from one of response frames received from said slave unit in response to said specific communication frame transmitted from said master unit, the number of stages of repeater units passed by the received response frames, to write information into said slave unit for setting a timing for returning the response frames from the slave unit to said master unit based on said number that has been read out; wherein said timing is set for each slave unit to return response frames in response to a communication frame from said master unit such that said master unit receives said returned response frames with no space between said returned response frames regardless of repeater delay times of each of said returned response frames.