Allen-bradley Company, LLC

Walter V Casto

Odo J Struger

Theodore J Markley

Lawrence W DeLong

A program protection module for a programmable controller checks the critical, or protected, portion of the control program each time the controller is switched to the run mode. This is accomplished by reading each control program instruction out of the controller memory and comparing it with a corresponding control instruction stored in a nonaccessible read-only memory. If all the compared control instructions are identical, the module sets a status bit in the programmable controller which enables the protected portion of the control program to be executed. If identity is not found, an alarm is generated and the protected program is not executed.

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Solon, OH, United States of America

Walter V Casto