What the message indicates
The reported sequence indicates insufficient space in the CPU load-memory path or its memory card after program additions. The evidence does not identify the CPU order number, installed card capacity, block sizes, or the exact text of the final message, so it cannot establish which memory resource is exhausted.
| Observation | Engineering interpretation | Next decision |
|---|---|---|
| The message appeared after adding program content | The changed program required more memory than was available. | Inspect the Blocks properties and compare the program requirements with the available load and main memory. |
| Deleting the additions did not clear the message | Load/delete operations can leave noncontiguous gaps, so total unused memory may not exist as one usable block. | Compress the load memory before concluding that the card lacks sufficient capacity. |
| A complete download is being attempted | The complete program may require more free space than downloading only the changed block. | If the change is isolated, download only the modified FC or FB. |
Why deleting blocks may not recover usable space
Repeated load and delete operations can create gaps between memory objects in load memory or RAM. Deleting the recent additions can therefore restore the old project content without producing a sufficiently large continuous free-memory area.
Compression removes these gaps and consolidates free memory into a continuous block. The available evidence states that compression can be performed with the CPU in RUN or STOP, but it does not identify CPU-specific restrictions; confirm the operating-state choice against the documentation for the installed CPU.
Respond to the compression prompt
The evidence supports confirming the “compress load memory” prompt as the direct corrective action for fragmented memory. It does not support treating compression as a guaranteed cure: the operation cannot create additional physical capacity when the program genuinely exceeds the installed load memory or memory-card capacity.
- Open the project’s Blocks area, select Properties, and inspect the reported memory requirements.
- Record the installed CPU and memory-card details; these are required if capacity must be checked.
- Confirm load-memory compression to consolidate gaps created by earlier load/delete operations.
- Retry the download. If only one FC or FB changed, download that modified block instead of the entire program.
Verify the result
Verification is successful when compression completes and the intended block or program downloads without the memory message. If the message remains, distinguish fragmentation from insufficient capacity: recheck the Blocks properties, identify whether a complete or block-only download is being requested, and compare the required memory with the installed CPU and card resources.
Do not select a replacement memory card from this evidence alone. Card compatibility and required capacity depend on the exact S7-300 CPU and the measured program requirements, neither of which was supplied.
FAQ
Can I confirm “compress the load memory” on an S7-300?
Yes. The supplied evidence identifies compression as the supported way to eliminate gaps between memory objects, and states that it can run with the CPU in RUN or STOP. Check the installed CPU documentation before choosing its operating state.
Why does “memory not enough” remain after I delete my changes?
Load/delete operations can leave fragmented free space. Compress the load memory so that the unused areas become one continuous free block, then retry the download.
What should I do if S7-300 memory compression does not fix the download?
Check memory requirements in Blocks > Properties and compare them with the installed CPU and memory-card resources. If the modification affects only one FC or FB, try downloading only that changed block instead of the complete program.