Industrial controller with program synchronized updating of back-up controller
AssigneeAllen-Bradley Company, Inc.
InventorsWilliam B. Cook, Mark A. Flood, Kenneth W. Batcher
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Abstract
An industrial control system employs a primary and secondary controller each having a processor and an I/O data table. Updating of the secondary processor's I/O data table is accomplished synchronously with execution of the program in the primary processor at a particular point in the program. A tracking of changes in the I/O data table of the primary processor is used to transmit only changes in the I/O table to the secondary processor thereby avoiding undue interruption of the executing program while preserving synchronicity.
Claims21
A primary industrial controller exchanging input and output signals with a controlled process and communicating with a secondary industrial controller over a link, the primary industrial controller comprising:
- (a) a memory holding:
- (i) a user program describing the control of the controlled process;
- (ii) an I/O data table holding values of the output signals exchanged with the controlled process;
- (iii) a flag table having flags indicating changes to the I/O data table caused by control of the controlled process after a first predetermined time;
- (b) a processor communicating with the memory and operating to:
- (i) execute the user program to write values of the output signals to the I/O data table according to the user program;
- (ii) set flags in the flag table indicating changes in the I/O data table caused by execution of the user program;
- and
- (iii) at a second predetermined time after the first predetermined time, transmit to the secondary industrial controller only the values of output signal in the I/O data table that have changed as indicated by the set flags of the flag table;
- wherein at an arbitrary switch-over time, the primary industrial controller ceases execution of the user program and the secondary industrial controller begins execution of the user program, the secondary industrial controller using transmitted values of the output signals.
A method of providing a back-up for a primary industrial controller exchanging input and output signals with a controlled process and communicating with a secondary industrial controller over a link, the primary industrial controller including a processor communicating with a memory, the memory holding a user program for describing the control of the controlled process, an I/O data table holding values of the input and output signals exchanged with the controlled process, and a flag table holding flags indicating changes to the I/O data table, the method comprising the steps of:
- (a) after a first predetermined time executing the user program to read and write to the O/O data table according to the user program;
- (b) setting flags in the flag table indicating changes in the I/O data table of step (a) caused by control of the controlled process;
- (c) at a second predetermined time after the first predetermined time, communicating to the secondary processor only the values of the I/O data table that have changed as indicated by the set flags of the flag table to the secondary processor;
- and
- (d) at an arbitrary switch-over time, causing the primary industrial controller to cease execution of the user program and the secondary industrial controller to begin execution of the user program, with the secondary industrial controller using transmitted values of the output signals.
Dependencies are inferred from the claim text.