Resolving Siemens LOGO! Soft Comfort rxtxSerial.dll 64-bit Error

Problem Overview

Siemens LOGO! Soft Comfort V7 (LSC V7) is a 32-bit Java application used to program, simulate, and document LOGO! 0BA5 / 0BA6 / 0BA7 / 0BA8 logic modules. On Windows 7 64-bit (Home Premium, Professional, Ultimate, or Enterprise), the application installs and launches without complaint, but any attempt to download a circuit diagram to a connected LOGO! base module—or upload a program from the module—fails with the following Java runtime exception in the LSC dialog window:

Error while loading panel data.
java.lang.UnsatisfiedLinkError: C:\Program Files (x86)\Siemens\LOGO Comfort_V7\bin\rxtxSerial.dll:
Can't load AMD 64-bit .dll on a IA 32-bit platform

The transfer is aborted before any byte is sent over the PC-to-LOGO! cable. The same dialog can also appear when LSC V7 attempts to enumerate the COM port to which the LOGO! PC cable (6ED1057-1AA00-0BA0) or the LOGO! USB cable (6ED1057-1AA01-0BA0) is attached.

Affected Configurations

The error does not occur on Windows XP 32-bit, on Windows Vista 32-bit, or on 64-bit Windows when running LOGO! Soft Comfort V8 (6ED1058-0BA08-0YA1) and later, which ship a fully signed and architecture-correct rxtx bundle.

Root Cause

The error is a Java Native Interface (JNI) loading failure. LSC V7 is a 32-bit Java application and the bundled JRE is the 32-bit edition of Sun Java 6. When the JRE calls System.loadLibrary("rxtxSerial"), it expects a DLL that matches its own bitness (x86 / IA-32). The file present in the installation directory, however, has been compiled for the x86-64 (AMD64) instruction set. Mixing a 64-bit native library with a 32-bit JVM raises an UnsatisfiedLinkError before any method from the library is even invoked.

The four most common ways a 64-bit DLL ends up in a 32-bit LSC V7 folder are:

1. A 64-bit build of rxtxSerial.dll is copied into the bin folder by a partial upgrade attempt, by a third-party installer, or by extracting a 64-bit LSC V8 distribution into the same directory.
2. The LSC V7 support DVD has both 32-bit and 64-bit DLLs in different subfolders and the user points the install or copy operation at the wrong source.
3. An operating system component (e.g., a Windows compatibility shim) or an anti-virus "repair" replaces the original 32-bit DLL with a 64-bit build.
4. Windows on Windows (WoW64) redirection does not apply because the DLL is referenced by an explicit absolute path, not by the standard search order.

The "panel data" wording in the dialog comes from LSC's wrapper around the RXTX CommPortIdentifier API. RXTX is the de-facto open-source Java library for serial port access and is bundled with LSC V7 to support COM-port communication with the LOGO! cable.

Technical Background: Java JNI, RXTX, and WOW64

Java applications cannot access the Win32 Communications API (kernel32.dll functions CreateFile, SetCommState, WriteFile, ReadFile, SetCommTimeouts, SetCommMask, WaitCommEvent, etc.) directly. They require a JNI bridge—a native DLL that exports C functions matching the Java method signatures declared in the corresponding Java class file. For serial I/O, LSC V7 uses the RXTX project, which provides:

• rxtxSerial.dll – native Windows serial port driver (x86 and x86_64 builds)
• rxtxParallel.dll – parallel port driver (not used by LOGO!)
• RXTXcomm.jar – Java classes (architecture-independent)

The RXTXcomm.jar class loader calls System.loadLibrary("rxtxSerial"). The Windows DLL search order is:

1. The directory from which the Java executable was loaded
2. The current working directory of the process
3. The %WINDIR%\System32 directory (for 64-bit processes) or %WINDIR%\SysWOW64 (for 32-bit processes on WOW64)
4. Each directory listed in the PATH environment variable

On Windows 7 64-bit, a 32-bit JVM is executed under the WOW64 subsystem. System32 is transparently redirected to SysWOW64 for 32-bit processes, but LSC V7 references the DLL through an absolute path: C:\Program Files (x86)\Siemens\LOGO Comfort_V7\bin\. That path is WOW64-aware (the literal (x86) is the convention) and is therefore resolved directly without redirection. The DLL at that exact path must be a 32-bit build; otherwise the loader aborts with the message "Can't load AMD 64-bit .dll on a IA 32-bit platform".

The Java HotSpot VM's own internal type RuntimeException wraps the underlying Win32 LoadLibrary error code, which on a 32-bit process attempting to load a 64-bit DLL is ERROR_BAD_EXE_FORMAT (Win32 error 193, 0xC1). Confirm this by inspecting the LSC log under %USERPROFILE%\.lsc\logs\ if the application is launched with -Djava.util.logging.config.file=... set.

Prerequisites Before the Fix

• Administrator account on the Windows 7 64-bit machine (you cannot replace files under Program Files (x86) without elevation).
• Local backup of the existing bin directory (the 64-bit DLL may still be useful for diagnostics).
• One of the following sources for a verified 32-bit rxtxSerial.dll:
  • Original LSC V7 installation DVD (subfolder typically named Support\RXTX\Win32 or install\Win32)
  • Siemens Industry Online Support entry for LOGO! Soft Comfort V7 (entry ID 109741041 and its linked FAQs)
  • A clean 32-bit installation of LSC V7 on another Windows 7 32-bit or Windows XP SP3 32-bit machine
• The Microsoft Sysinternals Sigcheck utility (or Visual Studio dumpbin) to confirm the architecture of the replacement DLL.

Solution: Replace the Native Library

1. Close LOGO! Soft Comfort V7 if it is running. Confirm via Task Manager that no java.exe, javaw.exe, or LSCE.exe process is active. The LSC launcher spawns the JVM and may keep it resident in the background for fast re-launch.
2. Open an elevated command prompt: Start → All Programs → Accessories → right-click Command Prompt → Run as administrator.
3. Back up the existing file. From the elevated prompt run:

   takeown /f "C:\Program Files (x86)\Siemens\LOGO Comfort_V7\bin\rxtxSerial.dll"
   icacls  "C:\Program Files (x86)\Siemens\LOGO Comfort_V7\bin\rxtxSerial.dll" /grant Administrators:F
   copy   "C:\Program Files (x86)\Siemens\LOGO Comfort_V7\bin\rxtxSerial.dll" "%USERPROFILE%\rxtxSerial.dll.bak"

4. Open C:\Program Files (x86)\Siemens\LOGO Comfort_V7\bin\ in Windows Explorer. Inspect the file size of rxtxSerial.dll: a 32-bit RXTX 2.2 build is typically 102,400 bytes (100 KB) and a 64-bit build is 110,592 bytes or 121,344 bytes depending on compiler version. If the file is larger than 100 KB it is almost certainly the wrong architecture.
5. Copy the 32-bit rxtxSerial.dll from the verified source (DVD, support download, or a known-good 32-bit install) into the bin folder. Right-click the new file, choose Properties → Unblock if the file originated from a download, otherwise Windows may refuse to load it as a SmartScreen-blocked file.
6. Confirm the file architecture with the Sysinternals Sigcheck tool (or dumpbin from Visual Studio):

   cd "C:\Program Files (x86)\Siemens\LOGO Comfort_V7\bin"
   sigcheck -m rxtxSerial.dll | findstr /i "MachineType"
   # or with dumpbin:
   dumpbin /headers rxtxSerial.dll | findstr "machine"

   A 32-bit DLL reports MachineType: 0x14c (IMAGE_FILE_MACHINE_I386); a 64-bit DLL reports 0x8664 (IMAGE_FILE_MACHINE_AMD64). If the output is anything other than 0x14c, repeat step 5 with a different source DLL.
7. Restart LOGO! Soft Comfort V7 and retry the download or upload operation.

where /R C:\ rxtxSerial.dll

Verification Procedure

1. In LSC V7, open any program (or use File → Open Sample Project → Examples → Lighting staircase).
2. Connect the LOGO! PC cable or LOGO! USB cable to the PC and to the LOGO! base module service port.
3. Power the LOGO! module from 24 V DC and navigate the front-panel display to PC ↔ LOGO! using the cursor keys.
4. In LSC V7, choose Tools → Transfer → PC → LOGO! (keyboard shortcut F11).
5. The transfer dialog must show the COM port number, the baud rate (default 19 200 for 0BA5/0BA6/0BA7), and the firmware version of the LOGO! module. The "Error while loading panel data" dialog must NOT appear.
6. After the download completes, the LOGO! module must run the program and its display must show RUN or the configured start text.
7. For upload, choose Tools → Transfer → LOGO! → PC (keyboard shortcut F12). The circuit diagram must open in the LSC editor with all function blocks, references, and parameters intact.

Alternative Solutions

Why a 32-bit DLL Works on 64-bit Windows

Windows 7 64-bit includes the WOW64 (Windows on Windows 64-bit) compatibility layer. 32-bit processes load 32-bit DLLs from the SysWOW64 and \Program Files (x86)\ trees without any explicit configuration. The LSC V7 installer already takes advantage of WOW64: it places the entire application under Program Files (x86) and registers the COM-port enumerator with the 32-bit registry hive (HKLM\SOFTWARE\Wow6432Node). Because the bundled JRE is 32-bit, only 32-bit native libraries can be loaded successfully. Replacing the 64-bit rxtxSerial.dll with a 32-bit build restores the bitness match and the JNI bridge loads normally. The substitution is safe; the file is not code-signed and Windows does not enforce signing for non-driver DLLs.

LOGO! Communication Stack Architecture

Error Code Reference

Troubleshooting Matrix

Permanent Fix: Upgrade to LOGO! Soft Comfort V8

The cleanest permanent solution is to upgrade to LOGO! Soft Comfort V8.x, which Siemens distributes as a fully signed 64-bit installer that matches the Windows 7/8/10/11 x64 runtime. The upgrade preserves all program logic because LSC V8 reads V7 project files (.lsc) directly. The Siemens LOGO! product page lists the current version, and Siemens Industry Online Support provides the download under your Service & Support entitlement. Validate the new version's release notes against your module's firmware before deploying in production.

If you must continue to run LSC V7 (for example, to support a fleet of installed 0BA5–0BA7 modules where the program is locked to LSC V7's password-protected format), the DLL-replacement procedure above is the supported workaround. Keep a clean copy of the 32-bit rxtxSerial.dll in your project documentation so that any future re-imaging of the engineering workstation can be completed in minutes.

Notes on Windows 7 Maintenance

Windows 7 SP1 has been in extended support and no longer receives new security fixes. A machine still running Windows 7 64-bit should at minimum be patched with the 2016 rollup and its successors as documented on Microsoft Learn — Windows 7 Home Premium update issues to keep the Win32 subsystem, Device Manager, and the WOW64 layer functional. Without these updates the COM-port enumeration that the LOGO! PC cable relies on can become unreliable, which can mask or amplify the native-library error described in this article. For new deployments, migrate to Windows 10 IoT LTSC 2019 or Windows 11 IoT on the engineering workstation.

FAQ