Communication system and slave and repeater units therefor

• US 20070047588A1
• Filed: 08/30/2006
• Published: 03/01/2007
• Est. Priority Date: 08/31/2005
• Status: Active Grant

• Current Assignee: Omron Corporation
• Original Assignee: Omron Corporation
• Inventors: Ozaki, Toshiyuki, Fujikawa, Masanori, Koga, Masao
• Granted Patent: US 7,792,155 B2
• Time in Patent Office: Days
• US Class Current: 370/501
• CPC Class Codes: G05B 19/41855 by local area network [LAN], network structure
• CPC Class Codes: G05B 2219/31127 Repeater between two networks
• CPC Class Codes: Y02P 90/02 Total factory control, e.g. smart factories, flexible manufacturing systems [FMS] or integrated manufacturing systems [IMS]

Abstract

A communication system is formed with a master unit having a communication function and at least one slave unit also having a communication function connected by a network including a bus. Repeater units are inserted on the network between the master unit and the slave unit in one or more stages. As the master unit transmits request frames downstream through the network to the slave unit, the slave unit control the timing of transmitting the response frames in response successively such that the master unit receives the response frames without waiting in between regardless of repeater delay times of each of the returned response frames determined by the number of stages of the repeater units. Each communication frame that is transmitted through the network contains identification data indicative of its type and each repeater unit serves to repeat certain types of received frames only in the upstream direction.

Claims

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 and said at least one slave unit in one or more stages;

wherein said master unit serves to transmit request frames in a downstream direction through said network to said at least one slave unit, response frames being transmitted from said at least one slave unit each in response to a corresponding one of said request frames;

wherein said repeater units serve to repeat said response frames only in an upstream direction through said network which is opposite said downstream direction, and

wherein communication frames of various types that include both said request frames and said response frames each contain identification data indicative of the type thereof.

2. The communication system of claim 1 wherein said master unit serves to read out from received one of said response frames the number of stages of repeater units passed by the received response frame, to calculate a time domain 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, and to write said time domain in one of said request frames.

3. The communication system of claim 2 wherein said time domain is set for each slave unit such that said master unit receives said returned response frames without waiting in between regardless of repeater delay times of each of said returned response frames determined by said number of the stages of the repeater units.

4. The communication system of claim 2 wherein said request frames are adapted to contain data on address values of the repeater units that have been passed and data on the number of stages of the repeater units;

wherein said repeater unit serves to store data on the address value of said repeater unit and the value of one plus the number of stages of the repeater units when one of said request frames passes through said repeater unit; and

wherein said slave unit serves to read out of said request frame data on the address value of the repeater unit adjoining in the upstream direction and on the number of repeater units and to cause said response frame to said master unit to contain data on the address value of the repeater unit adjoining in the upstream direction and the number of stages of the repeater units read out of said request frame.

5. The communication system of claim 3 wherein said communication frames include an in frame for transmitting input data of said I/O terminal unit by said slave unit;

wherein the slave unit serves to return said in frame containing said input data of said I/O terminal based on said time domain; and

wherein said repeater units repeat said in frame only in said upstream direction.

6. The communication system of claim 3 wherein said slave unit is adapted to transmit a connection frame for acknowledging existence of said slave unit to said master unit;

wherein said master unit serves to transmit a request frame for requesting said slave unit to transmit said connection frame;

wherein said communication frames include said connection frame and said request frame; and

wherein said repeater units repeat said connection frame only in said upstream direction.

7. 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 and said at least one slave unit in one or more stages;

wherein said network serves to transmit communication frames of various types therethrough, each of said communication frames containing identification data indicative of the type thereof;

wherein said repeater units serve to repeat some of said communication frames only in an upstream direction through said network, depending on the type thereof; and

wherein said slave unit stores the number of stages of said repeater units between said slave unit and said master unit and transmits response frames successively in response to request frames received from said master unit such that said master unit receives said response frames without waiting in between regardless of repeater delay times of each of said returned response frames determined by said number of the stages of the repeater units.

8. The communication system of claim 7 wherein said master unit serves to transmit a request frame to the slave unit for requesting transmission of a connection frame for acknowledging existence of said slave unit;

wherein said slave unit serves to transmit said connection frame to said master unit;

wherein said communication frames of various types include said connection frame and said request frame; and

wherein said repeater units repeat said connection frame only in said upstream direction.

9. The communication system of claim 7 wherein said communication frames include an in frame for transmitting input data of said I/O terminal unit by said slave unit;

wherein the slave unit serves to return said in frame containing said input data of said I/O terminal such that said master unit receives said response frames without waiting in between regardless of repeater delay times of each of said returned response frames determined by said number of the stages of the repeater units; and

wherein said repeater units repeat said in frame only in said upstream direction.

10. A slave unit for a communication system that includes a master unit which is a programmable controller having a communication function, at least one of said 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 and said at least one slave unit in one or more stages, said slave unit comprising:

a reception processing part that serves to read from a communication frame transmitted from said master unit a transmission time of said communication frame and the number of the stages of said repeater units that are passed by said communication frame; and

a transmission processing part that serves, when it is being requested to transmit a response frame in response to said communication frame from said master unit, to return a response without waiting in between regardless of repeater delay times determined by the number of the stages of the repeater units.

11. A repeater unit for a communication system that includes 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 other similar repeater units which are inserted on said network between said master unit and said at least one slave unit in one or more stages, said repeater unit comprising:

frame receiving means for receiving communication frames of various types containing identification data for identifying the types of said received communication frames; and

type identifying means for identifying the types of said received communication frames, said repeater unit serving to repeat received communication frames, if said received communication frames are identified to be of a type transmitted from said at least one slave unit to said master unit, only from a downstream direction to an upstream direction on said network.