Will CFC Clean Up Free S7-414 Data Work Memory in PCS 7?
No. In CFC V8.1, Options > Block Types > Clean Up removes unused block types from the offline chart and block folders; it does not remove instantiated control logic or reclaim CPU work memory. The Siemens manual distinguishes offline engineering data from the compiled program downloaded to the CPU. To recover memory, the project must be reviewed for actual program data and instances that can safely be removed or reduced; the available information is not enough to identify candidates or promise a 500 kB saving.
Table of Contents
- What CFC Clean Up Changes
- Why the Second Cleanup List Needs Care
- How to Investigate a Work-Memory Shortage
- Project-Level Reduction and Validation
- Verification
- Limitations and Operational Precautions
- Engineer FAQ
- Technical References
- Related Articles
- Related Tags
What CFC Clean Up Changes
The CFC V8.1 function manual describes two cleanup lists: block types in the chart folder that have no instances in charts, and offline block types not used in CFC charts. These actions clean the offline folders. Siemens separately describes compiling CFC charts to generate the program and downloading that program to the CPU. Therefore, removing an unused offline type alone does not reclaim runtime memory occupied by the loaded user program. The distinction matters: a block type is a definition; a chart block is an instance of that type.
Why the Second Cleanup List Needs Care
A type absent from CFC charts may still be called internally by another block. Siemens gives CTRL_PID (FB 61) calling OP_A_LIM (FB 46) as an example: deleting the caller's chart-folder type does not make the called type unnecessary. Review dependencies before removing any offline type. This is a project-maintenance concern, distinct from reducing memory used by the active CPU program.
How to Investigate a Work-Memory Shortage
First identify the exact S7-414 CPU order number and STEP 7, CFC, and PCS 7 versions, then capture the reported memory category and its available/used values from the engineering project or CPU diagnostics applicable to that setup. “Data work memory” should not be conflated with load memory, code, or engineering-folder size. Compare a current compile/resource report with the deployed project and determine which actual data structures or block instances account for the consumed data memory. The source gives no CPU variant, report, project, or candidate block, so no specific 500 kB reduction can be calculated here.
Project-Level Reduction and Validation
Only consider removing a chart instance, associated data, or an application feature after establishing that it is unused and not referenced by other logic, sequences, HMI, alarms, interlocks, or external interfaces. The exact checks depend on project configuration; the cited CFC manual does not establish a universal list of disposable PCS 7 blocks. Make changes in a controlled project copy, compile and review diagnostics, perform project-specific functional testing, and follow the site's approved backup, change-control, and download process before deployment. Do not treat CFC Clean Up as a substitute for that analysis.
Verification
After a project change, compare the same CPU's same memory category before and after compiling, and confirm the intended program is the one deployed. Verify affected sequence and operator functions through the project's approved test procedure. A successful cleanup of offline folders only verifies that unused types were removed from those folders; it does not prove that CPU data work memory was recovered or that a runtime program change was made.
Limitations and Operational Precautions
The source reports an S7-414 and a target of about 500 kB, but gives no exact CPU MLFB, STEP 7/CFC/PCS 7 versions, memory diagnostic, or project contents. Consequently, this article cannot identify safe blocks to delete, estimate savings, or prescribe a download mode. Removing logic or data can change process behavior. Back up the project, assess dependencies and process impact, and use authorized engineering and plant change-control procedures. The CFC V8.1 manual supports the explanation of Clean Up, but does not by itself establish applicability of its interface to every installed PCS 7/CFC version.
Engineer FAQ
Does Clean Up remove block instances from CFC charts? No. The documented cleanup candidates are unused block types in offline chart/block folders; instances are separate chart objects.
Can a block type missing from the chart folder still be required? Yes. A block type may be called internally by another type; Siemens' example is OP_A_LIM (FB 46) called by CTRL_PID (FB 61).
Will deleting a library type automatically reduce CPU data work memory? The manual describes folder cleanup, not a CPU memory reduction. The effect on the loaded program must be established by compiling and inspecting the actual project.
Can the 500 kB target be assessed from “S7-414” alone? No. The exact CPU model and its memory diagnostics, plus the configured program, are needed.
What evidence should be saved before deciding on a reduction? Record the CPU identifier, software versions, memory category and current usage, relevant compile diagnostics, and a dependency-reviewed list of candidate project data or instances.
Technical References
- Siemens, CFC for SIMATIC S7 (V8.1), Function Manual, 08/2014, §§4.1, 9.4.7, pp. 18, 107–108. The manual describes chart/block-folder cleanup, block-type versus instance distinctions, program compilation, and CPU download.
https://cache.industry.siemens.com/dl/files/154/90683154/att_21132/v1/s7jcfcab_en-US.pdf?download=true