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US 4,095,094 AGranted
Malfunction detection system for a programmable controller
AssigneeAllen-Bradley Company, Inc.
InventorsOdo J. Struger, William W. Searcy, Ernest F. John
Life of this patent
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AssigneeAllen-Bradley Company, Inc.
InventorsOdo J. Struger, William W. Searcy, Ernest F. John
Estimating the term…
A programmable controller includes a hardwired monitor module which connects to the I/O address decoder and the central logic unit of the controller. The monitor module detects malfunctions which cause deviations in the operation of these elements from a prescribed pattern, and in response generates a disabling signal which deenergizes all operating devices on the controlled system. A diagnostic module is also included and is comprised of a set of routines stored in the controller memory which periodically direct the controller to operate according to a prescribed pattern and to indicate deviations from that pattern as a malfunction. Such malfunctions are indicated in a diagnostic register which connects to the monitor module.
In a programmable controller having a memory which stores a control program that is continuously and repeatedly executed to direct a logic unit to operate operating devices on a controlled system in response to the logic states of sensing devices on the controlled system, the improvement therein comprising a diagnostic module for periodically checking the operation of said programmable controller while it is on line, said diagnostic module including means for periodically operating said logic unit in a prescribed pattern, said means including a first set of instructions stored in said memory with the control program which directs the logic unit to operate an output in a prescribed pattern, means for detecting deviations in the operation of said logic unit from said prescribed pattern including a second set of instructions stored in said memory which direct the logic unit to examine the logic state of said output, and a diagnostic register for indicating a malfunction when a deviation is detected, wherein the execution of said first and second set of instructions are interleaved with the execution of the control program instructions.
In a programmable controller having a memory which stores a control program that directs the programmable controller to operate a controlled system having sensing devices which connect with addressable input circuits on the programmable controller and having operating devices which connect to addressable output circuits on the programmable controller, the improvement therein comprising a monitor module having inputs which connect to selected elements of said programmable controller;
Dependencies are inferred from the claim text.