Kkula
Browse Questions » STEP 7 / STEP 7 Lite: Central processing unit goes Towards Halt mode due Towards Software Fault

About User

Siemens Self Support

Questions Asked: 37.9K

Answers Given: 32

Statistics

Tags

0
  • Open
Siemens Self Support
Asked:18 Oct 2025

STEP 7 / STEP 7 Lite: Central processing unit goes Towards Halt mode due Towards Software Fault

Hello,
Today one of our CPU 315 goes to stop mode due to SF . When i login in to plc program an dcheck the diagnostics buffer i found two events there: See the attach picture.
As i can understand the CPU goes to stop mode because of it can not load one DB and one OB from the programs but when i check the DB and OB in the same programs i did not found the DB and OB.
Can anyone help me to figure out the issue.

#sosflex #STEP 7 / STEP 7 Lite #siemens
1Answers 5Views 0Votes
0 Likes 0 Favourites 0 Followers 0 Comments
Answers(1)
Siemens Test Added an Answer on18 Oct 2025
Siemens Self Support - CPU 315 Stop Mode (SF)

CPU 315 Stop Mode due to SF Error

Hello,

The SF error indicates a system fault, specifically related to memory access. Based on your diagnostics buffer events, the CPU is halting due to inability to load DB and OB. The fact that you cannot find these in the current program suggests a few possibilities:

  • Program Inconsistency: The DB/OB might have been deleted or corrupted in a previous program upload or modification, but the CPU still has stale references.
  • Card/Memory Issue: A hardware fault in the CPU's memory or on a communication card could prevent proper loading.
  • Project Version Mismatch: You might be online with a different project version than what’s actually running on the PLC.

Recommended Actions:

  1. Cross-Reference Check: Use the cross-reference feature in TIA Portal to verify if the missing DB/OB are actually called anywhere in your code. This will confirm the CPU’s expectations.
  2. Complete Download: Perform a "Complete Download" (not just a hardware and software download) to ensure the entire program, including all DBs and OBs, is uploaded to the PLC.
  3. Check for Multiple Projects: Verify you have the correct project open in TIA Portal.
  4. Hardware Diagnostics: Run a hardware diagnostics test on the CPU and any connected communication modules.
  5. Siemens Support: If the issue persists, please open a support request with Siemens Support, providing the diagnostics buffer content and the project version.

For further information, refer to Siemens Support Article: PLC stops in STOP mode due to a system fault (SF)

Sincerely,
Siemens Self Support

0