Resolving FbDrive Module Driver Generation Errors and CFC Editor Crashes in PCS 7 V9.0

In SIMATIC PCS 7 V9.0 SP2, when compiling CFC charts with 'Generate module drivers' results in the deletion of driver interconnections on FbDrive blocks (FB1881) and causes the CFC Editor to crash or hang with 'chart is open already' upon connecting PZDIn1, the failure is caused by missing symbolic addressing in HW Config or an outdated Basis Library driver generator. To resolve this, assign explicit symbolic names to all drive I/O words in HW Config, install PCS 7 V9.0 SP2 Update Collection 03 (UC03) or later to resolve known driver generator bugs with third-party GSDML files, and recompile CFC charts with 'Generate module drivers' enabled.

Executive Summary

In SIMATIC PCS 7 Advanced Process Library (APL), the channel block FbDrive (FB1881) interfaces with variable frequency drives (such as Danfoss VLT/VACON, Siemens SINAMICS, or third-party PROFIBUS/PROFINET drives) using standard drive telegrams (e.g., Telegram 1 or Telegram 20). When configuring FbDrive according to standard Siemens guidelines, connecting the primary input word PZDIn1 to the first word of the drive's peripheral address is designed to trigger automated generation of remaining interconnections (PZDIn2, PZDOut1, PZDOut2, Mode, DataXchg) and instantiate diagnostic @ charts.

However, in PCS 7 V9.0 SP2, engineers frequently report a fatal failure: connecting PZDIn1 immediately causes the CFC Editor to crash. When reopening the chart, STEP 7 warns that 'the chart is open already'. Subsequent compilations with 'Generate module drivers' fail, deleting existing driver interconnections across all FbDrive instances. This issue stems from a combination of unassigned I/O symbols in HW Config and an XML driver generation defect in early PCS 7 V9.0 SP2 Basis Library releases. This guide details the exact diagnosis and remediation steps required to stabilize the driver generator.

Architecture and Fundamental Mechanics

The PCS 7 driver generator manages FbDrive interconnections through automated hardware profile matching:

Automated Drive Driver Generation Mechanics:
- FbDrive requires interconnection with hardware drive telegrams defined in HW Config.
- When an engineer connects PZDIn1 to the address of the first peripheral input word (e.g., IW 512), the CFC Editor invokes the driver generator in the background.
- The driver engine queries the STEP 7 Symbol Table to verify the module type, scans the hardware catalog profile (GSDML or internal XML), and automatically generates the downstream connections to PZDIn2, PZDOut1, PZDOut2, and system diagnostic block MOD_DRV in system chart @(1).
The Symbolic Name Prerequisite:
- If the peripheral address assigned in HW Config does NOT have an associated symbolic name in the Symbol Table, the driver generator's macro parser fails to resolve the module hardware identifier (LADDR).
- Instead of completing the link, the generator enters an infinite loop or encounters an unhandled null-pointer exception, causing s7tgtopx.exe and the CFC Editor (s7cfcapp.exe) to crash abruptly.
Basis Library Bug in PCS 7 V9.0 SP2 and UC03 Resolution:
- In early releases of PCS 7 V9.0 SP2, the Basis Library driver generator contained a known software defect when processing certain third-party drive GSDML files (such as Danfoss VLT FC-300). The XML parser failed on telegram length definitions, resulting in memory corruption during driver generation.
- Siemens resolved this issue in PCS 7 V9.0 SP2 Update Collection 03 (UC03) by releasing updated Basis Library driver generator binaries (s7driver.dll).

Step-by-Step Implementation Procedure

Follow these steps to eliminate driver compilation crashes and configure FbDrive successfully:

Clear Orphaned Chart Lock Handles:
- If the CFC Editor crashed and reports 'chart is open already', open Windows Task Manager (Ctrl + Shift + Esc).
- Under the 'Details' tab, terminate any instances of s7cfcapp.exe, s7tgtopx.exe, and s7ussapx.exe.
- In SIMATIC Manager, perform 'File > Save As... > with Reorganization (slow)' to clear database lock stubs.
Assign Symbolic Names in HW Config:
- Open HW Config for the automation station.
- Locate the drive station (e.g., Danfoss VLT or SINAMICS on PROFINET/PROFIBUS).
- Select the drive telegram slot (e.g., Standard Telegram 1, 2 Words IN / 2 Words OUT).
- In the lower address table, right-click the first input word (e.g., IW 512) and select 'Edit Symbols...'.
- Assign clear symbolic names to all input and output words (e.g., VFD01_PZD_In1, VFD01_PZD_In2, VFD01_PZD_Out1, VFD01_PZD_Out2).
- Select 'Station > Save and Compile'.
Install PCS 7 V9.0 SP2 Update Collection 03 (UC03):
- Verify your installed Basis Library version in SIMATIC Manager ('Help > About > Installed Software').
- Download and install SIMATIC PCS 7 V9.0 SP2 Update Collection 03 (UC03) on the Engineering Station.
- Reboot the Windows operating system after update installation.
Update Master Data Library Block Types:
- Open the Master Data Library in SIMATIC Manager.
- Verify that the latest Basis Library and APL blocks are present.
- Select 'Options > Charts > Update Block Types...' to synchronize all project charts.
Interconnect FbDrive in CFC:
- Open the destination CFC chart.
- Insert FbDrive (FB1881).
- Connect the symbolic tag VFD01_PZD_In1 to pin PZDIn1.
- The CFC Editor will now successfully auto-generate remaining connections (PZDIn2, PZDOut1, PZDOut2, Mode, DataXchg) without crashing.
Compile and Download:
- Select 'Chart > Compile > Charts as Program...'.
- Select 'Entire program' and verify that 'Generate module drivers' is CHECKED.
- Confirm that compilation finishes with 0 Errors and that @ charts containing MOD_DRV are created.
- Download changes to CPU 410-5H in RUN mode.

Verification

In CFC chart, inspect the FbDrive block: confirm that pins PZDIn1, PZDIn2, PZDOut1, and PZDOut2 display valid interconnections to HW Config symbols.
Open the generated chart @(1): confirm that the MOD_DRV block exists and monitors the drive's diagnostic address.
Open CFC in Test Mode (Online): confirm that FbDrive receives live status words from the VFD and displays Quality Code 16#80 (Good).
In WinCC Runtime: verify that the VFD faceplate displays speed feedback, operating mode, and electrical current accurately.

Limitations and Operational Precautions

Never attempt to bypass module driver generation by manually wiring raw peripheral addresses without symbols; doing so prevents the generation of diagnostic and watchdog blocks, leaving the drive unprotected against communication loss. If plant policy prohibits installing UC03 immediately, use the vendor-specific drive block library (e.g., Danfoss PCS 7 Library) as an approved alternative. Engineering licenses and library options should be verified through an authorized Siemens distributor or the Siemens Industry Mall.

Engineer FAQ

Why did the CFC Editor crash when connecting PZDIn1 on FbDrive?

Because the connected hardware address lacked a symbolic name in HW Config, or the Basis Library driver generator encountered a known bug in early V9.0 SP2 releases when parsing third-party GSDML files.

What update resolves the FbDrive driver generation crash?

SIMATIC PCS 7 V9.0 SP2 Update Collection 03 (UC03) or later resolves this driver generator defect.

How do I clear the 'chart is open already' warning after a crash?

Terminate lingering s7cfcapp.exe processes in Windows Task Manager and execute 'Save As... with Reorganization (slow)' in SIMATIC Manager.

Does connecting PZDIn1 automatically populate PZDIn2 and PZDOut?

Yes. In standard PCS 7 APL, connecting PZDIn1 to a valid symbol triggers the driver generator to populate the remaining telegram words automatically.