Programs

Programs are logical programming units that describes operations between variables of a process.

Programs describe one of the following operations:

Sequential: Continuous and sequential execution of the program steps and operations during an execution cycle.
Cyclic: Execution of programs at each target system cycle.

Programs at the beginning of a cycle (before sequential programs) typically describe preliminary operations on input devices to build high-level filtered variables. Sequential programs frequently use these variables. Programs at the end of the cycle (after sequential programs) typically describe security operations on the variables operated on by sequential programs, before sending values to output devices.

Main sequential programs (at the top of the hierarchy) are executed according to their respective dynamic behavior. Programs before and after sequential programs commonly describe cyclic operations. These cyclic programs are not time-dependent. Cyclic programs are systematically executed at the beginning of each run time cycle.

Within devices, programs are linked together in a hierarchical tree. Programs placed at the top of the hierarchy are activated by the system. Child programs (lower level of the hierarchy) are activated by their parent.