Method for comparing, an automation system and a controller

An automation system comprising a controller, said controller having stored therein an application for controlling a process within the automation system, the application program cyclically performing task scans based on an input signal, characterised in that the system comprises:

• means for inputting to at least two different versions of the application, which versions reside within the controller, an input signal obtained from said process,
• means for executing, in the controller, a task scan corresponding to said input signal for each of the at least two different versions of the application in parallel, each said version of the application outputting a variable value,
• means for storing in memory locations the variable values obtained from the execution of the task scan for each of said at least two versions, said memory locations being known by the controller,
• means for retrieving from the memory locations the variable values from the different versions of the application, and
• means for comparing said retrieved variable values and determining if differences exists between the variable values when the controller is idle, the comparisons being made as an atomic operation in-between task scans.

A controller for controlling processes within an automation system, said controller comprising an application and an input/output arrangement, the application program cyclically performing task scans based on an input signal, characterised in that said controller comprises:

• at least two different versions of said application, said versions being arranged to receive the same data from said input/output arrangement,
• means for executing the same task scan based on said input signal for the at least two different versions of the application program, each version outputting a variable value based on said input signal,
• means for storing in memory locations the variable values obtained from the execution of said at least two versions, said memory locations being known by the controller,
• means for retrieving from the memory locations the variable values from the different versions, and
• means for comparing the variable values when said controller is idle, the comparison being made as an atomic operation in-between tasks.