Allen-bradley Company, LLC

Michael E Schultz

Steven M Zink

Arthur P Pietrzyk

Paul J Tletski

James A Stermole

A programmable controller senses the status of input devices and controls the state of operating devices in accordance with a stored ladder logic control program. A memory of the programmable controller contains message data and data defining a set of expected transitions of the status of selected input devices. An instruction of the ladder logic initiates execution of a machine language message program which causes the programmable control to inspect the states of the selected input devices to determine whether an expected transition has taken place. When one of the expected transitions occurs, the message data and an identification of the selected input device are sent to a personal computer connected to the programmable controller. The personal computer uses the the data from the programmable controller to formulate an alphanumeric message which is presented to the operator on a display device.

Programmable controller with an operator messaging function

A programmable controller for sensing the status of input devices and controlling the state of operating devices in accordance with a stored ladder logic control program includes a state machine instruction. A memory is provided for storing data regarding each state of an apparatus being controlled. This data defines the status of apparatus operating devices for each state, and the legitimate transitions from that state to other selected states, along with a Boolean logic expression of selected input conditions which determines when a state transition should occur. A processor responds to the state machine instruction by examining the truth of the Boolean logic expressions for the present state of the apparatus to detect if a state transition should occur. Upon such a detection controller advances to the state associated with the detected true expression. State transitions also can be defined as occurring upon a specified change in the status of a single input. Other mechanisms are provided to detect illegitimate states of the apparatus and take appropriate action.

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Euclid, OH, United States of America

Michael E Schultz