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Controller RSLogix Controller Tags Controller Fault Handler Power-Up Handler Tasks Continuous Program_01 Program Tags MainRoutine Program_02 Program Tags MainRoutine Periodic Unscheduled Programs Program Tags Main HMI Motion Groups Trends Data Types User-Defined Strings Predefined Module-Defined I/O Configuration The RSLogix 5000 controller organizer (Figure 15-6) displays the project organization in a tree format showing tasks, programs, routines, data types, trends, I/O configuration and tags. Each folder groups common functions together. This structure simplifies the navigation and the overall view of the whole project. In front of each folder, there is an icon containing a 1 sign or a 2 sign. The 1 sign indicates that the folder is closed. Click it to expand the tree display and display Continuous task scan Program 1 Program 2 Program 32 Continuous task Task auto-restart 336 Part 1  Memory and Project Organization the files in the folder. The 2 sign indicates that the folder is already open and its contents are visible. Clicking on the right mouse button brings up many different, context-sensitive popup menus. Often, you find that this is a shortcut to access the property window or menu options from the menu bar. Tasks Tasks are the first level of scheduling within a project. A task is a collection of scheduled programs. When a task is executed, the associated programs are executed in the order listed. This list of programs is known as the program schedule. Tasks provide scheduling based on specific conditions and do not contain any executable code. Only one task may be executing at any given time. The number of tasks a controller can support depends on the specific controller. The main types of tasks (Figure 15-7) include: • Continuous tasks execute nonstop but are always interrupted by a periodic task. Continuous tasks have the lowest priority. A ControlLogix continuous task is similar to the File 2 in the SLC 500 platform. Here the continuous task is named Main Task. • Periodic tasks function as timed interrupts. They interrupt the continuous task and execute for a fixed length of time at specific time intervals. • Event tasks also function as interrupts. Rather than being an interrupt on a timed basis, an event task is triggered by an event that happened or failed to happen. Programs Programs are the second level of scheduling within a project. The function of the folders under Main Task is to determine and specify the order in which the programs Figure 15-6  Controller organizer tree.  Figure 15-7  Continuous and periodic tasks. Periodic task scan 5 ms 10 ms 15 ms ... Program 1 Program 2 Periodic Program 32 task


Petruzella_ProgrammableLogicControllers__5e
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