Communication system

• US 6,301,610 B1
• Filed: 02/11/2000
• Issued: 10/09/2001
• Est. Priority Date: 02/11/2000
• Status: Expired due to Fees

• Current Assignee: Ansaldo STS SPA
• Original Assignee: Union Switch & Signal, Inc. (Hitachi, Ltd.)
• Inventors: Ramser, Stephen F., Davenport, Andy L.
• Primary Examiner(s): Eng, David Y.
• Application Number:
  US09/502,386
• Time in Patent Office: 606 Days
• Field of Search: 709/208, 714/18
• US Class Current: 709/208
• CPC Class Codes: G05B 19/05 Programmable logic controllers, e.g. simulating logic interconnections of signals according to ladder diagrams or function charts
• CPC Class Codes: G05B 2219/1214 Real-time communication between plc, Ethernet for configuration, monitor
• CPC Class Codes: G05B 2219/1215 Master slave system

Abstract

A communication system includes a first communication device, a second communication device, and a communication channel, such as modems and a telephone line, between the devices. The first device includes: a first memory for storing first information, a first processor, and a first communication controller for transmitting a message. The first processor periodically determines a plurality of values, and a count of any of those values which changed after a previous determination of those values. The first processor also alternatively selects for transmission in the message, as a function of the count, either (i) all of the values, or (ii) the values which changed. The second device includes: a second memory for storing second information, a second communication controller for receiving the message, and a second processor. The second processor alternatively updates the stored second information with either (i) all of the values, or (ii) the values which changed of the message. The second processor also processes the stored second information.

Claims

1. A communication system comprising:

a first communication device including;

first memory means for storing first information,

first processor means (a) for repetitively determining a plurality of values as at least some of said first information, (b) for determining a count of any of said values which changed after a previous determination of said values, and (c) for alternatively selecting for communication in a message, as a function of said count, either (i) all of said values, or (ii) said any of said values, and

first communication means for communicating said message;

a second communication device including;

second memory means for storing second information,

second communication means for communicating said message, and

second processor means (a) for alternatively updating said stored second information with either (i) all of said values, or (ii) said any of said values of said message, and (b) for processing at least some of said stored second information of said second memory means; and

a communication channel between said first and second communication means.

2. The communication system of claim 1, wherein said first communication device is a master communication device;

wherein said second communication device is a slave communication device; and

wherein said first communication means sends said message to said second communication means over said communication channel.

3. The communication system of claim 2, wherein said master and slave communication devices are master and slave programmable logic controllers (PLCs).

4. The communication system of claim 1,

wherein said values are a plurality of first values;

wherein said message is a first message;

wherein said second processor means includes;

means for determining a plurality of second values,

means for determining whether any of said second values has changed,

means for alternatively selecting for communication with a second message either (i) all of said second values, or (ii) said any of said second values, and

means for processing (for control) at least some of said stored second information;

wherein said first communication means includes means for sending said first message to said second communication means, and means for receiving said second message from said second communication means;

wherein said second communication means includes means for sending said second message to said first communication means, and means for receiving said first message from said first communication means; and

wherein said first processor means includes;

means for alternatively updating said stored first information with either (i) all of said second values, or (ii) said any of said second values, and

means for processing at least some of said stored first information.

5. The communication system of claim 4, wherein said first processor means further includes means for periodically updating said stored first information with said all of said second values.

6. The communication system of claim 4, wherein said second processor means further includes means for determining whether greater than a predetermined count of said second values has changed, and means for informing said first processor means that greater than the predetermined count of said second values has changed.

7. The communication system of claim 6, wherein said first processor means further includes means for requesting all of said second values after being informing by said second processor means that greater than the predetermined count of said second values has changed;

and wherein said second processor means further includes means for sending said first processor means said all of said second values in a subsequent second message.

8. The communication system of claim 6, wherein said second processor means further includes means for preparing said second message including a status indicating that greater than the predetermined count of said second values has changed.

9. The communication system of claim 8, wherein said second processor means further includes means for preparing said second message including a count of said second values which have changed, and said any of said second values.

10. A communication system comprising:

a first programmable logic controller including;

first memory means for storing first information,

first processor means (a) for repetitively determining a plurality of values as at least some of said first information, (b) for determining which ones of said values changed after a previous determination of said values, and (c) for selecting for communication in a message said ones of said values which changed, and

first communication means for communicating said message;

a second programmable logic controller including;

second memory means for storing second information,

second communication means for communicating said message, and

second processor means (a) for updating said stored second information with said ones of said values which changed, and (b) for processing at least some of said stored second information of said second memory means; and

means for communicating information between said first and second communication means.

11. The communication system of claim 10, wherein said first processor means includes means for alternatively selecting for communication with said message either (i) all of said values, or (ii) said ones of said values which changed;

and wherein said second processor means includes means for alternatively updating said stored second information with either (i) all of said values, or (ii) said ones of said values which changed of said message.

12. The communication system of claim 10, wherein said first programmable logic controller is a master programmable logic controller;

wherein said second programmable logic controller is a slave programmable logic controller; and

wherein said first communication means sends said message to said second communication means by employing said means for communicating information.

13. The communication system of claim 10,

wherein said values are a plurality of first values;

wherein said message is a first message;

wherein said second processor means includes;

means for determining a plurality of second values,

means for determining whether any of said second values has changed,

means for selecting for communication with a second message said any of said second values, and

means employing at least some of said stored second information for control;

wherein said first communication means includes means for sending said first message to said second communication means, and means for receiving said second message from said second communication means;

wherein said second communication means includes means for sending said second message to said first communication means, and means for receiving said first message from said first communication means; and

wherein said first processor means includes;

means for updating said stored first information with said any of said second values, and

means employing at least some of said stored first information for display.

14. The communication system of claim 13, wherein said first processor means further includes means for alternatively updating said stored first information with either (i) all of said second values, or (ii) said any of said second values.

15. The communication system of claim 14, wherein said first processor means further includes means for periodically updating said stored first information with said all of said second values.

16. The communication system of claim 13, wherein said second processor means further includes means for sending said second message in response to said first message.

17. The communication system of claim 13, wherein said second processor means further includes means for determining whether greater than a predetermined count of said second values has changed, and means for informing said first processor means that greater than the predetermined count of said second values has changed.

18. The communication system of claim 17, wherein said first processor means further includes means for requesting all of said second values after being informing by said second processor means that greater than the predetermined count of said second values has changed;

and wherein said second processor means further includes means for sending said first processor means said all of said second values in a subsequent second message.

19. The communication system of claim 17, wherein said second processor means further includes means for preparing said second message including a status indicating that greater than the predetermined count of said second values has changed.

20. The communication system of claim 19, wherein said second processor means further includes means for preparing said second message including a count of said second values which have changed, and said any of said second values.

21. The communication system of claim 17, wherein said predetermined count is about ten.

22. The communication system of claim 10, wherein said means for communicating information includes a first modem communicating with said first communication means, a second modem communicating with said second communication means, and a communication line electrically connected between said first and second modems.