Access S7 Data Blocks from SIMIT Without Treating Them as PLCSIM I/O

SIMIT SP V10's standard PLCSIM coupling is for I/O signals defined by the simulated PLC's configured hardware; importing a SIMATIC Manager .asc symbol table does not turn arbitrary DBxxxx.DBX, DBW or DBD variables into supported PLCSIM coupling signals. Do not relabel DB addresses as inputs or outputs. If the design can use SIMIT's Virtual Controller instead of the external PLCSIM coupling, the V10.2 manual documents importing DB data from STEP 7 STL sources; that is a different simulation architecture and its applicability to the exact V10 installation must be confirmed.

Why the ASC Symbol Table Does Not Import the DB Contents

The ticket describes SIMIT SP V10, SIMATIC Manager and the PLCSIM coupling. Siemens' SIMIT V10 operating manual describes .asc and .seq files as symbol-table formats for SIMATIC projects, while its PLCSIM coupling section says I/O signals can be entered manually or imported from the project's symbol table. The SIMIT V10.2 manual further states that, with PLCSIM coupling, data exchange is possible only for I/O signals defined by configured hardware. A symbol table import is not a general import of PLC data-block structures or arbitrary DB addresses.

Keep DB Addresses and Physical I/O Semantics Separate

DBxxxx.DBX, DBxxxx.DBW and DBxxxx.DBD identify data-block locations; I and Q addresses describe input and output areas. Copying DB values into I/O addresses would change the program interface and may affect the real or simulated application logic. It is not an equivalent way to make a DB available to SIMIT. Decide whether the simulation must exchange data through the PLC's configured I/O image or needs access to PLC DB state; those are distinct interface requirements.

Option: Use the Existing PLCSIM Coupling for Configured I/O

When the exchange can be represented by configured hardware I/O:
1. Load the SIMATIC Manager project and its system data blocks (SDBs) into PLCSIM so the simulated hardware configuration is present.
2. In SIMIT, configure a PLCSIM coupling and import the project symbol table in a supported format, such as .asc, or enter required I/O signals manually.
3. Select signals that belong to the configured I/O address space. The manual states that the PLCSIM coupling exchanges only I/O signals defined by the configured hardware.
4. Start PLCSIM before starting the SIMIT simulation, and keep PLCSIM running while the SIMIT simulation is active.
5. Verify data exchange using a known input/output signal and confirm that its configured hardware address and value correspond to the intended simulated behavior.
This method does not expose arbitrary DB variables as PLCSIM coupling signals.

Option: Use SIMIT Virtual Controller DB Import (V10.2 Documentation)

If direct DB access is essential and it is acceptable to use SIMIT's Virtual Controller rather than the standard PLCSIM coupling, Siemens' SIMIT V10.2 manual documents importing DB data from STEP 7 STL sources:
1. Generate STL sources in STEP 7 that include all utilized data-block sources and any required structure definitions, such as UDTs.
2. Open the SIMIT Virtual Controller and its DB tab.
3. Click STL import, select the STL source, enter the data block number, select the direction, and enter the start and end bytes.
4. Click Import and check the resulting signals and data types. Siemens notes that existing signals in the specified byte range are overwritten and that addresses are not validated.
The manual describes this for a Virtual Controller; it does not establish that importing STL adds DB exchange to the external PLCSIM coupling. The document is for SIMIT V10.2, so confirm feature availability and exact steps for the installed SIMIT V10 release before changing the simulation design.

Choose the Simulation Interface Before Reworking the PLC

Use PLCSIM coupling where the model exchanges signals through configured hardware inputs and outputs. Consider Virtual Controller DB import only when the simulation architecture is intended to represent the controller in SIMIT and the exact product release supports the required DB source format. If the test requires simultaneous execution of the original PLC program in classic PLCSIM and access to internal DB variables, the cited SIMIT V10 documentation does not establish a direct DB coupling path for that combination. Do not silently change PLC code or map DB data onto I/O just to make the interface appear in SIMIT.

Expected Results and Verification

With PLCSIM coupling, verify that the imported or manually configured signal is an I/O address present in the loaded hardware configuration and that the expected value transfers between PLCSIM and SIMIT. With a Virtual Controller, verify the selected DB number, direction, byte interval, imported address list and data types against the STEP 7 source. Since the manual warns that addresses are not validated and the selected range may overwrite existing signals, review those signals before using them in simulation logic.

Verification

Confirm which coupling type is active in the SIMIT project and record the SIMIT/PLCSIM versions. For PLCSIM coupling, confirm the configured hardware, loaded SDBs and I/O addresses. For Virtual Controller DB import, inspect the source STL, DB number, direction, byte range and any imported structures. Run a controlled signal check and confirm the receiving logic uses the intended data. A successful import alone does not establish correct mapping or behavior.

Limitations and Operational Precautions

The source says SIMIT V10 but gives no minor release, PLCSIM version, CPU family or detailed coupling configuration. The available Siemens V10.0 and V10.2 operating-manual records were found, but the PDF host did not allow full-document retrieval in this research session; V10.0 returned a file-size error and Siemens support-host PDFs returned access errors. The V10.2 Virtual Controller instructions must not be generalized to the V10.0 PLCSIM coupling. Preserve the original project, inspect DB signal ranges before import and validate any architecture change in a controlled simulation environment.

Engineer FAQ

Can an .asc symbol-table import expose arbitrary DB variables in SIMIT's PLCSIM coupling? The cited SIMIT V10 documentation describes the PLCSIM coupling for I/O signals and does not establish general DB-variable exchange through that coupling.

Why should I not change DBX tags to I or Q addresses? DB and I/O addresses have different program meanings. Remapping them changes the PLC interface and is not an equivalent import workaround.

Can SIMIT Virtual Controller import DB data? The SIMIT V10.2 manual documents DB import from STEP 7 STL sources in the Virtual Controller's DB tab. This is distinct from the external PLCSIM coupling.

What can be overwritten during Virtual Controller STL import? Siemens warns that existing signals in the specified memory area between the selected start and end bytes are overwritten.

Does an STL import validate the DB addresses? The cited SIMIT V10.2 manual explicitly notes that imported addresses are not validated; compare them with the STEP 7 DB layout.

Technical References

Siemens, SIMIT Simulation Platform (V10.0) Operating Manual, 06/2018, A5E44876196-AA, §2.13.2.1 “File formats for signals” and §2.8 “PLCSIM coupling”; SIMIT/PLCSIM signal formats and symbol-table import context. The PDF could not be fetched because the web tool reported content length too large: https://cache.industry.siemens.com/dl/files/317/109759317/att_956837/v1/SIMIT_enUS_en-US.pdf
Siemens, SIMIT Simulation Platform (V10.2) Operating Manual, 03/2020, A5E44876249-AB, §3.8.1–3.8.2 “PLCSIM coupling” and §3.6.3.2 “Importing DB data from STL sources”; PLCSIM I/O scope and Virtual Controller DB import procedure. Siemens-hosted copy returned access error; indexed manual extract was available: https://support.industry.siemens.com/cs/attachments/109780242/SIMIT_enUS_en-US.pdf
Siemens, SIMIT TIA Data block (DB) Coupling, Entry ID 109988815, V10 document; a separate DB-coupling example whose applicability is not established for classic PLCSIM and the ticket's configuration: https://cache.industry.siemens.com/dl/files/815/109988815/att_1329059/v4/109988815_DB_Coupling_DOC_V10_en.pdf

Access S7 Data Blocks from SIMIT Without Treating Them as PLCSIM I/O