WinAC RTX 2005: Restoring SFC14/SFC15 Online Without CP5611

WinAC RTX 2005: Restoring SFC14/SFC15 Online Without a Physical CP5611

1. Problem Statement

Engineers using STEP 7 V5.4 / SIMATIC Manager against a WinLC RTX 2005 (V4.2) soft-PLC on a development PC frequently observe the following behavior: the standard library blocks SFC14 (DPRD_DAT) and SFC15 (DPWR_DAT) are visible in the offline program view of the Blocks folder, but the moment the user clicks Online (or downloads the program and then opens the online block list) the two SFCs vanish from the online folder. The SFCs cannot be dragged from the Standard Library, cannot be copied to the online PLC, and any call site that previously compiled cleanly may now show a "block not found" indicator.

This symptom is most often encountered by teams that develop S7 programs on an office PC (no PROFIBUS hardware installed) and ship a SIMATIC Microbox 420 with a CP5611 to the customer site. The development PC is meant to behave like the target, but STEP 7 treats the missing CP5611 as a hardware gap and hides the PROFIBUS consistent-data SFCs from the online block folder.

The SFCs are not missing by design, and they are not corrupted in the project. The root cause is the way WinLC RTX 2005 conditionally loads the PROFIBUS consistent-data firmware sub-system. The fix is to add the CP5611 as a sub-module of WinLC RTX 2005 in HW Config, which causes the firmware to be linked into the running image and re-enables the online visibility of the SFCs — even on a PC where the CP5611 card is physically absent.

2. Background: WinAC RTX 2005 Architecture

WinAC RTX 2005 is the Windows Automation Center / Real-Time eXtension bundle that turns a SIMATIC industrial PC into a software-based S7-300 / S7-400 controller. The bundle consists of three principal components:

• WinLC RTX 2005 (Windows Logic Controller, RTX variant) — the real-time SoftPLC that executes the S7 user program. It behaves like an S7-300 / S7-400 CPU on the slot of the PC-based backplane.
• WinAC RTX 2005 — the broader software package that bundles WinLC with the Ardence (later TenAsys) RTX real-time subsystem, the configuration tools, and the PROFIBUS driver suite.
• CP5611 / CP5613-A2 / CP5621 drivers — the PROFIBUS DP master drivers that connect the SoftPLC to a physical PROFIBUS network.

WinLC RTX 2005 runs the S7 user program deterministically on the RTX real-time subsystem. STEP 7 V5.4+ in SIMATIC Manager treats the SoftPLC exactly as it would an S7-400 CPU for the purposes of hardware configuration, online block management, and diagnostics. The PROFIBUS interface is logically inserted into the S7-300 / S7-400 rack of the SoftPLC in HW Config, even though the actual data path exits through a CP5611 on the PCI / PCIe bus (or, on modern SIMATIC PCs, an integrated PROFIBUS interface).

The CP5611 (Siemens part number 6GK1 561-1AA01) is the low-profile PROFIBUS DP master interface that historically ships with the SIMATIC Microbox 420, SIMATIC Panel PC 677 / 877, and SIMATIC Rack PC 847. The CP5613-A2 (6GK1 561-3AA01) is the higher-performance variant for applications requiring dual-channel PROFIBUS or higher bus scan rates. WinLC RTX 2005 will only load and execute SFC14 / SFC15 if it believes that one of these interfaces — or the integrated PROFIBUS interface of a SIMATIC PC — is present as a sub-module of its own rack, regardless of whether the underlying driver successfully attaches to a real bus.

3. Understanding SFC14 and SFC15

3.1 SFC14 — DPRD_DAT (Read Consistent Data from a DP Slave)

SFC14 reads the entire consistent data area of a DP slave starting at LADDR. The length of the consistent area is determined by the configuration of the slave's module in HW Config (the "Complete" consistency setting). The function is synchronous — it blocks the OB1 scan for the duration of the read, which is why consistent-data access is typically performed in OB1 only for short records (≤ 32 bytes) and in OB61 / OB62 for longer ones.

3.2 SFC15 — DPWR_DAT (Write Consistent Data to a DP Slave)

SFC15 writes a complete consistent data record to a DP slave. Like SFC14, the data is only transferred to the I/O when the entire block is in the consistent area, which is essential for coordinated motion commands, valve actuation, or any operation where the application must not see a partial update.

3.3 Common RET_VAL error codes

These error codes are returned identically whether the SFCs run on a physical S7-400 CPU, a WinLC RTX 2005 soft-PLC, or a SlotPLC CPU 412-6. The SFC firmware is identical across all three targets and lives inside the CPU firmware image.

4. Root Cause of the Disappearing SFC14/SFC15

The online view of the CPU's block folder is generated by STEP 7 from the diagnostic data that the SoftPLC reports. WinLC RTX 2005 maintains an internal map of which firmware functions it has loaded. SFC14 and SFC15 are part of the PROFIBUS DP firmware sub-system, and that sub-system is only instantiated when the WinLC firmware image detects that a PROFIBUS master sub-module is configured in its own rack.

The mechanism can be summarized in three points:

1. The SFC14 / SFC15 firmware code is conditionally linked into the running WinLC image at startup.
2. The trigger for inclusion is the presence of a CP5611 (or CP5613-A2, or the integrated PROFIBUS interface of a SIMATIC PC) configured as a sub-module of WinLC RTX 2005 in HW Config.
3. Without that sub-module, the firmware sub-system is not loaded, the SFC14 / SFC15 code is not present, and the online diagnostic list reports them as "not available". STEP 7 then shows them as missing blocks in the online view.

This is why the SFCs are visible offline (the offline project can reference them by symbolic name) but vanish online. The offline SFCs in the program editor are not copies of the firmware — they are placeholder objects in the Standard Library used purely for the symbolic binding in the source code. The actual executable code lives only in the CPU firmware, and that firmware is not loaded if the PROFIBUS master is not configured.

A common misconception is that an engineer can copy SFC14 / SFC15 from the Standard Library into the online PLC. You cannot. They are read-only firmware functions; any attempt to "download" them results in no transfer at all. The only way to make them available online is to ensure that WinLC RTX 2005 has the right sub-module configured so that it loads the PROFIBUS firmware image.

5. Solution Overview

There are three engineering options when no physical CP5611 is available on the simulation PC:

1. Recommended — Configure the CP5611 as a sub-module of WinLC RTX 2005 in HW Config. The CP5611 driver is allowed to be "downloaded" without the card being physically present, provided that the WinLC RTX 2005 itself is the configured CPU. This was the behavior already observed on WinLC 4.1 Basis and remains the supported method under WinAC RTX 2005 V4.2 with Service Pack 2 (Siemens entry ID 26992994).
2. Add a virtual PROFIBUS master (CP5613-A2 or the integrated interface of a SIMATIC PC) as a sub-module. On SIMATIC PCs with an integral PROFIBUS interface, the integrated interface is the preferred sub-module choice because it does not require an additional PCI slot.
3. Use a hardware surrogate CP5611 in a PCI slot of the development PC. Acceptable if a spare card is available; the driver does not need to attach to a working bus, only to be present on the PCI bus.

The first option is the most common because it does not require additional hardware. The configuration is done once in HW Config and stored in the STEP 7 project. The same project can then be downloaded to the office PC (simulation, no card) or to the Microbox 420 (production, card present) without any code changes.

6. Step-by-Step Configuration Procedure

6.1 Prerequisites

• STEP 7 V5.4 SP5 or later installed (required for WinAC RTX 2005 V4.2)
• WinAC RTX 2005 V4.2 with Service Pack 2 installed on the development PC
• WinLC RTX 2005 licensed and running (license is managed via the Automation License Manager)
• CP5611 driver installed (the driver package is included on the WinAC RTX 2005 DVD under \Drivers\CP5611)
• A STEP 7 project in SIMATIC Manager with the WinLC RTX 2005 station already inserted

If WinAC RTX 2005 is not yet installed, obtain Service Pack 2 from the Siemens Industry Online Support entry ID 26992994 and apply it before continuing. The SP2 update contains the CP5611 and integrated-PROFIBUS handling improvements that make the configuration robust against the case where the physical card is absent. The full SP2 description and download link is available at the Siemens support page for entry 26992994.

6.2 Procedure

1. Open SIMATIC Manager and load the project that contains the WinLC RTX 2005 station.
2. Double-click the Hardware object inside the WinLC RTX 2005 station to launch HW Config.
3. In HW Config, open the hardware catalog on the right-hand side. Navigate to:
   • For CP5611: PROFIBUS DP \ CP5611 (under Interface Submodules)
   • For integrated interface: PROFIBUS DP \ Integrated PROFIBUS Interface (on supported SIMATIC PCs)
   • For CP5613-A2: PROFIBUS DP \ CP5613-A2
4. Drag the chosen sub-module to an empty slot in the WinLC RTX 2005 rack (typically slot 2 or slot 3 — slot numbering is flexible as long as it does not collide with the CPU in slot 1).
5. When prompted, set the PROFIBUS address of the CP5611 (default 1 is acceptable for a development PC). If no DP slaves are configured, leave the PROFIBUS subnet as a new subnet or attach to an existing one.
6. If a DP slave (or multiple slaves) is needed in the simulation, insert the slave(s) on the new PROFIBUS subnet. Configure at least one slot of the slave with a module of consistency "Complete" — this is what triggers the SFC14 / SFC15 visibility at the firmware level.
7. Save and compile the HW Config (Station \ Save and Compile).
8. Download the hardware configuration to the WinLC RTX 2005: PLC \ Download to Target System. Even on a PC with no CP5611, this download succeeds and WinLC reports "Online".
9. After the download, place the CPU in RUN (or RUN-P).
10. Switch back to SIMATIC Manager, select the Blocks folder, and click Online. The online block list should now include SFC14 and SFC15.

6.3 Why "Download Without Hardware" Works

The CP5611 driver in WinAC RTX 2005 is a soft driver: it can be configured, downloaded, and brought to an operational state in HW Config regardless of whether a physical CP5611 is plugged in. The driver only attempts to bind to the PCI device when WinLC RTX 2005 actually starts scanning the PROFIBUS, and even then it tolerates a missing card by reporting the bus as "not connected". The CPU firmware, however, sees the configured sub-module and links in the PROFIBUS consistent-data SFCs. The two operations — driver configuration and driver binding — are deliberately decoupled in the WinAC RTX architecture.

7. Verification

After the configuration change, verify that the SFCs are present and callable:

1. In SIMATIC Manager, select the Blocks folder of the WinLC RTX 2005 station.
2. Click PLC \ Online in the toolbar, or use the Online button.
3. STEP 7 opens the online block view. Confirm that the list includes SFC14 (DPRD_DAT) and SFC15 (DPWR_DAT) with the system icon (lightning bolt or "S" mark in the block-icon column).
4. Open the program editor on any block that calls SFC14 or SFC15. The call should now resolve and STEP 7 should not display a red "block not found" indicator.
5. From a test OB, place a temporary call to SFC14 with a configured LADDR (e.g., 256) and download the OB. In a VAT, force RET_VAL to 0 after the call; the SFC executed. If RET_VAL is non-zero, the SFC ran but the underlying PROFIBUS stack could not be reached — the important point is that the SFC is present and callable.
6. Optional: From the Windows control panel Set PG/PC Interface, verify that the CP5611 (PROFIBUS) interface is selected as the access point for WinLC RTX 2005.

8. WinLC vs WinAC — Clearing Up the Terminology

A frequent question in this context is the difference between WinLC and WinAC. The Siemens naming is as follows:

The RTX suffix is critical: WinLC without RTX is a non-deterministic SoftPLC that runs as a Windows thread. WinLC RTX is the real-time variant suitable for hard real-time PROFIBUS scanning. For SFC14 / SFC15 usage, only WinLC RTX is supported. WinAC RTX 2005 V4.2 requires the bundled RTX 8.1 SP2 or later (matched to the WinAC RTX DVD); older RTX versions do not expose the CP5611 sub-module configuration correctly.

9. Firmware and Service Pack Considerations

WinAC RTX 2005 V4.2 was released as the second major release of the platform and shipped on a single DVD. Two service packs were subsequently released; Service Pack 2 (SP2) is the most widely deployed and contains the fixes referenced in the official Siemens release notes (entry ID 26992994). Among the items addressed in SP2:

• Improved handling of the CP5611 sub-module configuration when the physical card is absent.
• Support for the integrated PROFIBUS interface of newer SIMATIC PCs as a sub-module of WinLC RTX.
• Clock-master / clock-slave operation refinements when the CP5611 is used as a sub-module (WinAC RTX can act as clock master or clock slave on PROFIBUS, provided the CP5611 or the integrated PROFIBUS interface is configured as a sub-module of WinLC RTX).
• Compatibility updates for STEP 7 V5.4 SP5 and SP6.
• Stability fixes for SFC14 / SFC15 access in the absence of a connected PROFIBUS bus.

The Siemens Industry Online Support entry 26992994 ("ServicePack 2 for WinAC RTX 2005") is the canonical download location for the SP2 installer. Always deploy SP2 before commissioning a WinAC RTX 2005 development PC, particularly when the PC will be used for offline simulation only.

10. Alternative Workarounds

If the CP5611 sub-module configuration is not feasible in the development environment, the following workarounds can be used. None of them are as clean as the recommended solution, but they are documented in field practice.

10.1 Stub the SFC calls

Replace SFC14 / SFC15 calls with wrapper FBs that:

• In simulation mode: copy the RECORD to / from a DB and return RET_VAL = 0.
• In production mode: call the real SFC14 / SFC15.

The wrapper FBs are typically implemented in SCL or STL. The downside is that the offline program does not match the production program 1:1, which complicates code review and validation. A common variant is to put the wrapper selection behind a compile-time switch (e.g., a global flag in a separate DB or a conditional call guarded by a CPU-type check).

10.2 Use a USB-PROFIBUS adapter

A USB-PROFIBUS adapter such as the Siemens PC-Adapter USB A2 (6GK1 571-2BA00) can be used in place of a CP5611. In HW Config, configure the CP5611 sub-module even though the physical layer is the USB adapter; the SFC14 / SFC15 firmware still loads, but DP traffic is sent over USB. Latency and determinism suffer; the adapter is acceptable for slow-rate slaves only (typically update times of 50 ms or longer). The PC-Adapter USB A2 is fully supported by WinAC RTX 2005 SP2.

10.3 Deploy a second CP5611 in the office PC

The cleanest development workflow is to install a CP5611 in the office PC and pull a real PROFIBUS cable to a small DP slave test bench (for example, a single ET200S with one digital I/O module). The SFC14 / SFC15 calls then execute against real hardware, the simulation is more realistic, and the office PC is identical in configuration to the Microbox 420. This is the preferred production-engineering setup for any team that ships multiple Microbox 420 systems.

11. Field Commissioning Notes

When the Microbox 420 arrives on site and the office-developed project is downloaded to the production machine, pay attention to the following:

Always perform a final "online against production" test on site to confirm that the SFCs are not only present in the online view, but also functional. A passing "online block list contains SFC14 / SFC15" check at the office is necessary but not sufficient; the production cabinet needs the bus-scan loop to close the validation. Confirm the slave diagnostic buffer is clear and that RET_VAL is 0 for the test call before handing the cabinet over to operations.

12. Compatibility Matrix

13. Troubleshooting Matrix

14. OB and Diagnostic Considerations

The PROFIBUS SFCs are tightly coupled to OB82 (diagnostic interrupt), OB83 (insert / remove interrupt), OB85 (priority class error), and OB86 (rack failure). When WinLC RTX 2005 has a CP5611 sub-module configured but the physical bus is absent, the WinLC will report a "DP master system error" at startup and trigger OB86 with a rack failure OB86_FLT_ID = 0x39 (DP master system failure). To prevent OB86 from stopping the CPU in a simulation environment, configure OB86 as a "permanently assigned" OB with a "no reaction" or "substitute value" behavior.

OB82 is triggered when a DP slave reports a diagnostic event. In simulation, with no slaves present, OB82 is not called. The diagnostic buffer of WinLC RTX 2005 can be read from STEP 7 with PLC \ Module Information \ Diagnostic Buffer, or programmatically with SFC51 (RDSYSST) reading SSL ID 0x00A0. The buffer is a reliable first stop when investigating "SFC14 returns 80A1" issues.

OB61 and OB62 (synchronization to DP cycle) are also relevant. WinLC RTX 2005 supports OB61/OB62 with the same semantics as the S7-400 CPU. The OB61 constant bus cycle time (T_DP) is configured in HW Config under the DP master properties. The minimum T_DP is 1 ms, and 5 ms is a typical safe value for simulation.

15. Glossary

• Consistent data: A block of process data transferred to / from the I/O as a single, atomic unit, with no intermediate updates visible to the application.
• DPRD_DAT: Standard SFC for reading consistent data from a DP slave (SFC14).
• DPWR_DAT: Standard SFC for writing consistent data to a DP slave (SFC15).
• HW Config: The hardware configuration editor inside STEP 7 / SIMATIC Manager.
• Microbox 420: A fanless SIMATIC IPC used as a PC-based controller in harsh environments.
• SoftPLC: A software-only PLC runtime that executes on a general-purpose PC under a real-time OS.
• Sub-module: In S7-300 / S7-400 terms, an interface module that occupies a slot in the CPU rack and provides a logical interface to a peripheral.
• WinAC RTX 2005: Siemens bundle that includes the WinLC RTX soft-PLC, RTX real-time subsystem, and PROFIBUS drivers.