Programs
Programs are logical program organization units (POUs) describing operations between
variables in a process. Programs describe the cyclic operations that execute at each target
system cycle.
Cyclic programs systematically execute at the beginning of each run-time cycle and are not
time-dependent.
Programs at the beginning of a cycle generally describe preliminary operations on input
devices to build high level filtered variables. Programs at the end of the cycle generally
describe security operations on the variables. Programs at the end of the cycle also send
the values to output devices.
Describe programs using the available graphic or literal languages. Specify the programming
language while creating the program. Changing the Programming language is not supported.
POUs defined as programs execute on the
Trusted®
controller, The POU
adheres to the order shown in the Programs
section of the Application View
.
The hierarchical tree links programs. The system activates the programs at the top of the
hierarchy. Parents activate child POUs lower in the hierarchy.Programs have these naming conventions and limitations:
- Unique names limited to eight characters beginning with a letter or single underscore followed by letters, digits, and single underscores.
- Names cannot include reserved words, defined words, or data types.
- A maximum of 255 programs in a project.
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