Resolving STEP 7 V5.4 SR3 SCL Timestamp Conflict Errors

Overview

STEP 7 V5.4 Service Release 3 (SR3) combined with the SCL V5.3 SP3 compiler (release K5.3.3.0) introduces a stricter block consistency check that produces a persistent "time-stamp conflict between the source code and the offline block" error when SCL source files are compiled and downloaded to an S7-300 or S7-400 CPU. The same SCL source compiles and downloads cleanly on a station running STEP 7 V5.4 SR1 with SCL V5.3 SP1 (release K5.3.1.0 or K5.3.1.1). The error is not a CPU firmware fault, a project integrity issue, or a network problem — it is a development-environment artifact caused by changes in the SCL compiler's interface-regeneration logic, combined with Windows time-zone metadata and the stricter consistency check introduced in SR3.

This article documents the symptom signature, the affected tool versions, the byte-level root cause in the S7 block header, the diagnostic procedure to isolate which factor is dominant on a given engineering station, and the field-proven resolution methods ranked from least to most invasive. The SCL V5.3 SP4 Hotfix 1 distributed under Siemens Entry ID 27461704 is the long-term fix. For projects on a newer code line, the SIMATIC STEP 7 Professional V20/2021 SR3 Combo under Siemens Entry ID 109973520 is the supported successor path.

Problem Description

The failure is reproducible on demand and exhibits a stable signature. The SCL source file compiles without syntax errors in SCL V5.3 SP3, but the subsequent download to the target CPU fails with one of the following messages reported in the SIMATIC Manager diagnostic pane:

• "The online and offline blocks have different timestamps. Do you want to overwrite the online block?" — selecting Yes re-prompts the same question on the next download cycle.
• "Time-stamp conflict between the source code and the offline block." — reported when the SCL source is opened directly and File > Download is invoked.
• "The block in the CPU is not consistent with the offline block." — reported by the Block Consistency tool when the source is refreshed.

Field observation: the block runs in monitor mode after force-acknowledging the timestamp warning, so the application logic is correct. The conflict reasserts itself on the next online-edit cycle or the next full download, which makes it a deployment blocker rather than a runtime fault.

Identical SCL logic compiled in SCL V5.3 SP1 on a separate engineering station completes the full compile-download-monitor cycle with no warnings. This rules out application logic, target hardware, and project structure, and points to the SCL compiler behavior and the SCL/STEP 7 interaction layer as the cause.

Affected Versions and Components

Service packs and hotfixes are distributed as standalone entries in the Siemens Industry Online Support portal. The recommended upgrade path is SCL V5.3 SP4 Hotfix 1, published under Siemens Entry ID 27461704. The SR3 Combo for the modern code line is the SIMATIC STEP 7 Professional V20/2021 SR3 Combo, published under Siemens Entry ID 109973520.

Root Cause Analysis

Three independent factors combine to produce the persistent conflict. Each is documented separately so the field engineer can isolate which factor is dominant on a given station. In practice, two of the three are typically active on a single PC, and resolution requires addressing the dominant factor first.

Factor 1 — SCL Interface Regeneration Logic in SP3

When SCL compiles a .scl source to an FB or FC, it regenerates the interface description (IN, OUT, IN_OUT, STAT, TEMP, RETURN) and writes the result into the offline block container. In SCL V5.3 SP3, the regeneration routine was updated to write a fresh interface timestamp on every compile, even when the interface itself is unchanged. The interface timestamp is what STEP 7 compares against the source's Last Modified timestamp during the consistency check.

Because the SCL source's filesystem timestamp is captured at edit time but the compiled interface timestamp is captured at compile time, a mismatch is normal during a single edit-compile cycle. STEP 7 resolves this through the source/compiled-block association stored in the S7 program's source folder. The association can break in two cases:

1. The .scl source was moved or copied outside the S7 program source folder, severing the association.
2. The SCL compiler re-writes the block with a timestamp that the offline/online compare logic in SR3 rejects even though the association is intact.

Factor 2 — Windows Time Zone and DST Settings

SCL stores the source timestamp using the Windows system clock at the time the file is saved. STEP 7 stores the offline block timestamp using the Windows system clock at the time the block was generated. Both are local-time values with no explicit zone tag. If the engineering PC has its time zone or DST setting changed between editing the source and compiling the block — or differs from the time zone used when the project was originally saved — the two timestamps will not line up even after a clean compile. STEP 7's compare logic in V5.4 SR3 treats this as a hard conflict; earlier service releases sometimes tolerated it.

Engineering stations that travel between customer sites and the home office are particularly exposed. A laptop configured for Pacific time on a customer visit and Eastern time back in the office will produce a consistent 3-hour skew on every SCL compile until the time zone is restored.

Factor 3 — Block Header / Interface Section Drift

SCL V5.3 SP3 also introduced a stricter interpretation of multi-instance DBs and array bounds. The compiler may insert a hidden initialization vector into the FB's static section when the source contains arrays, even if the source syntax is identical to V5.3 SP1. The added static instance triggers an interface-version bump that the consistency check then flags as a timestamp conflict between the source declaration and the regenerated block.

Block Header and Timestamp Internals

Understanding the byte layout of the S7 block header turns a confusing error into a deterministic diagnosis. An S7 FB/FC block starts with a 36-byte header followed by the interface description and then the code body. The relevant fields for the timestamp conflict are:

The two interface-timestamp fields at 0x000A and 0x000E are the pair that STEP 7 compares during the consistency check. In SCL V5.3 SP1, the compiler wrote the source date to both fields when the interface was unchanged. In SCL V5.3 SP3, the compiler writes a fresh compile date to 0x000A on every compile, regardless of whether the interface changed. STEP 7's SR3 consistency check compares 0x000E (source date) against 0x000A (compile date) and refuses to download when the delta exceeds the configured threshold (default 0 seconds in SR3, default 60 seconds in SR1).

The interface-version field at 0x0016 is incremented by the SCL compiler whenever the interface section changes. A version bump combined with a timestamp mismatch is a strong signal that Factor 3 is active. A timestamp mismatch without a version bump indicates Factor 1 or 2.

Diagnostic Procedure

Run the following checks in order. Each check produces an objective answer that determines the next step.

1. Capture both SCL compiler versions. Open the SCL editor, choose Help > About, and record the full version string (for example, SCL V5.3 SP3 K5.3.3.0). Repeat on the working station. If the failing station is on a later service pack than the working station, the migration itself is the candidate cause.
2. Capture both Windows time zones. Run tzutil /g in an elevated command prompt on each engineering station. Also confirm Windows time service synchronization with w32tm /query /status and verify that the system clock matches real time within 1 second. Record the local time on both stations at the moment of testing.
3. Capture block and source timestamps. In the SIMATIC Manager offline view, right-click the affected FB > Object Properties and record the Last Modified timestamp. In Windows Explorer, right-click the .scl source > Properties and record Modified. The two should be within a few seconds of each other after a fresh compile. A delta greater than 60 seconds is suspicious.
4. Run the Block Consistency tool. Right-click the S7 program > Check Block Consistency. Note which blocks are flagged. If only the SCL-generated blocks are flagged, the SCL compiler is the dominant factor. If system blocks (SDB, SFB, SFC) are also flagged, the time-zone or DST issue is more likely.
5. Compare with a known-good reference station. Export the .scl source, the compiled FB, and the offline/online comparison report to a network share and diff the contents in a hex editor. The interface area in the FB (offset 0x0000 to 0x001F) is where the timestamp and interface version bytes live. A byte-level diff between a working and a failing FB pinpoints which field has changed.
6. Check the SCL Options. In the SCL editor, choose Options > Customize. Confirm that Create block is set to Always and that Block generation is not set to Manual. A manual generation mode combined with SR3's stricter check is a frequent false positive.
7. Test in PLCSIM. Create a local S7-PLCSIM instance, download the offline project to PLCSIM, and observe whether the timestamp warning re-appears. If PLCSIM downloads cleanly but the physical CPU does not, the issue is on the CPU/online side (CPU clock, protection level, or online block left over from a previous session).

Resolution Methods

Apply the resolutions in the order listed. Each method is non-destructive until the final download step.

Method 1 — Re-associate Source with Compiled Block

1. In SIMATIC Manager, navigate to S7 Program > Sources.
2. Right-click the affected .scl source > Check Block Consistency > select Yes to compile and replace the offline block.
3. Right-click the regenerated FB > Object Properties > verify the timestamp now matches the source's modified time within 1 second.
4. Download to the CPU and acknowledge the timestamp warning if prompted. The conflict should not recur on subsequent download cycles.

Method 2 — Recreate the Block from Scratch

1. Export the .scl source and back up the S7 program.
2. Delete the offline FB in the Blocks container. Do not delete the .scl source.
3. Open the SCL source and recompile. The compiler regenerates a clean block with fresh timestamps.
4. Re-instantiate the FB in OB1 or the calling block, regenerate the instance DB, and download.

This method eliminates any stale block-header artifacts left by the previous SCL version. It is the most reliable on stations that have been migrated through multiple SCL service packs.

Method 3 — Synchronize Windows Time Zones

1. Set both engineering stations to the same Windows time zone.
2. Disable automatic DST adjustment during the project handoff, or apply the DST offset manually to the project file timestamps using a tool that preserves binary block headers (only as a last resort, on a backup copy).
3. Recompile the SCL source. The conflict should clear on the next consistency check.
4. Re-enable DST adjustment after the project handoff is complete.

Method 4 — Update SCL to V5.3 SP4

1. Download SCL V5.3 SP4 Hotfix 1 from Siemens Entry ID 27461704.
2. Close all SIMATIC applications, including SIMATIC Manager, the SCL editor, and any open NetPro sessions.
3. Run the hotfix installer with administrator privileges. The installer requires a valid STEP 7 V5.4 license to be present.
4. Restart the engineering station and verify the SCL version is now K5.3.4.0 or later via Help > About.
5. Recompile the source. SP4 reverts the interface-regeneration behavior to be tolerant of source/compile-time skew while preserving the stricter consistency check from SR3.

Method 5 — Upgrade STEP 7 to V5.5 or V5.6

For projects that can absorb a STEP 7 upgrade, V5.5 SP1 and later normalizes the consistency-check algorithm and ships a current SCL compiler. Long-term, the SIMATIC STEP 7 Professional V20/2021 SR3 Combo, distributed as Siemens Entry ID 109973520, is the supported successor for migration planning. The Combo is downloaded free of charge with a Siemens Support account and consolidates the SR3 fixes for STEP 7, SCL, PLCSIM, and NetPro into a single installer.

SCL Array-Handling Errors on V5.3 SP1

A separate but related failure is observed on stations that stay on SCL V5.3 SP1 (K5.3.1.0) instead of moving to SP3. The compiler reports array-bound errors on sources that compiled cleanly on K5.3.1.1. The root cause is a difference in how the two SP1 sub-revisions treat array dimensions declared with symbolic constants versus literal constants. The K5.3.1.0 revision flags some symbolic-constant array dimensions that K5.3.1.1 accepts as valid. The recommended fix is to move the affected PC to the K5.3.1.1 minor revision (re-install the SCL V5.3 SP1 package) or upgrade to K5.3.3.0 with the SP4 hotfix applied.

Workaround for sites that cannot upgrade: declare the array dimension with a literal constant in the affected source. The literal form is accepted by all V5.3 SP1 and SP3 revisions. Track the change in the project README so the next engineer does not revert the declaration back to a symbolic constant.

Verification Procedure

1. After applying any of the resolution methods, perform a full project download: PLC > Download in SIMATIC Manager.
2. Open the CPU online view (PLC > Online & Diagnostics) and confirm the affected FB shows the expected code timestamp in the block header.
3. Open the SCL source in monitor mode (Debug > Monitor) and toggle a known input to confirm online monitoring works without the timestamp warning re-appearing.
4. Cycle power on the CPU if the project uses remanent instance DBs. Confirm the instance DB is regenerated and that the FB call resolves correctly.
5. Open a VAT or watch table that exercises the affected FB and verify the outputs respond as expected.
6. Save the project to the versioned archive with a comment that records the SCL and STEP 7 versions used. This prevents the next engineer from re-introducing the conflict by editing the source on a mismatched tool.

Troubleshooting Matrix

Field Commissioning Notes

Three commissioning practices prevent the timestamp conflict from appearing at the customer site in the first place.

• Lock the development environment. Standardize all engineering stations on the same STEP 7 + SCL service pack combination. Document the combination in the project README and in the project archive manifest. A station that drifts to a newer SCL release than the rest of the team is the most common source of project-wide conflict reports.
• Lock the engineering station clock. Lock the Windows time zone and DST setting via Group Policy on engineering workstations. Field engineers who travel should set the clock to the customer's time zone at the start of the visit and back to the home office time zone at the end, then recompile the affected sources after each change.
• Recompile on the target station. Always recompile the .scl source on the same station that will perform the download. Do not move compiled blocks between stations, even over a fast network. The compiled block header is sensitive to the source station's clock and to the SCL release of the source station. A clean recompile on the target station is faster than diagnosing a cross-station conflict.

For multi-engineer projects, add a pre-commit check to the project release process: open each .scl source, choose File > Check Block Consistency, and confirm no warnings are reported. A clean consistency check before the archive step catches the conflict before it reaches the customer.

Related SCL and STEP 7 Considerations

The timestamp conflict is sometimes reported alongside other SCL V5.3 SP3 behaviors that share the same root cause — changes in interface handling. Three are worth noting for the field engineer.

• Multi-instance DB regeneration. SCL V5.3 SP3 regenerates the multi-instance DB for any FB that contains a nested FB instance, even if the nested FB signature is unchanged. The regenerated instance DB has a fresh timestamp that triggers the same conflict pattern. The fix is identical: re-associate the source and recompile.
• Symbolic constant propagation. SCL V5.3 SP3 propagates symbolic constants more aggressively into the interface section, which can change the interface version field even when the source syntax is unchanged. The fix is to upgrade to SCL V5.3 SP4 via Siemens Entry ID 27461704.
• Library compatibility. FBs that come from a Siemens library (Standard Library, PID Control, Communication) carry their own SCL compile history. If the project was last built on SCL V5.3 SP1 and the engineer is now on SP3, the library FBs are flagged in the consistency check even though the source is in the library, not in the project. The fix is to either keep the engineering station on V5.3 SP1 or rebuild the library FBs from their STL exports after moving to SP3.

Frequently Asked Questions