The present inventors have recognized that highly reliable operation may be further achieved in industrial control systems by monitoring execution of programs in real time. Such monitoring may include detecting defective program sequences which may be caused by executing a wrong sequence, executing a sequence at a wrong time, and/or a faulty clock. In one aspect, a control program may be divided into executable modules. A first code stream may then execute to control an industrial process or machine using the executable modules stored in a first set. In addition, a second code stream may execute to verify the first code stream using executable modules stored in a second set. First and second execution sequence values may be generated based on execution of the first and second code streams. A comparison of the first and second execution sequence values may detect an error which may have occurred in the program.

The present inventors have recognized that highly reliable operation may be further achieved in industrial control systems by monitoring execution of programs in real time. Such monitoring may include detecting defective program sequences which may be caused by executing a wrong sequence, executing a sequence at a wrong time, and/or a faulty clock. In one aspect, a control program may be divided into executable modules. A first code stream may then execute to control an industrial process or machine using the executable modules stored in a first set. In addition, a second code stream may execute to verify the first code stream using executable modules stored in a second set. First and second execution sequence values may be generated based on execution of the first and second code streams. A comparison of the first and second execution sequence values may detect an error which may have occurred in the program.