Resolving Sinumerik 840D PLC Upload Error in STEP 7 V5.5

Problem Identification: Sinumerik 840D PLC Upload Failure

When attempting to upload the integrated PLC program from a Sinumerik 840D controller equipped with a PCU50 using STEP 7 V5.5 and an MPI PC Adapter (6ES7972-0CA23-0XA0 or equivalent), the operator receives a hardware-not-recognized alarm. The fault prevents the standard "Upload Station to PG" operation from completing, leaving the PLC program unreadable through the conventional STEP 7 V5.5 path.

The 840D's integrated PLC is not a stand-alone S7-300 CPU that STEP 7 recognizes out of the box. The PLC is embedded in the NC subsystem and exposes a virtual station type (NCU-specific profile) that STEP 7 V5.5 can only resolve when the matching Hardware Support Package (HSP) from the Sinumerik Toolbox is installed. Without this HSP, STEP 7 aborts the upload with an error referencing an unknown or unsupported module type.

The "BS" suffix referenced in operator queries is ambiguous. Within Siemens nomenclature, 840D controllers are typically designated as 840D Powerline (PL) or 840D sl Solution Line. Both ship with PCU50 (Powerline) or PCU50.3 / newer PCUs (sl) running HMI Advanced or Sinumerik Operate respectively. The "BS" label is commonly a plant-specific or region-specific designation, occasionally interpreted as a user or vendor shorthand for a Powerline variant. The procedures in this article apply to 840D Powerline with PCU50 running HMI Advanced; 840D sl users should adapt to the Sinumerik Operate menu paths described in the HMI series startup section.

Root Cause Analysis

The alarm during PLC upload is generated by one of the following root causes:

The most frequent root cause for the described alarm is the first item: the STEP 7 V5.5 hardware catalog does not contain the Sinumerik PLC station type, so the S7 upload logic fails to deserialize the system data blocks (SDBs) returned from the controller.

Sinumerik Toolbox and Hardware Support Package (HSP) Installation

The Sinumerik Toolbox is the official Siemens delivery that contains:

• STEP 7 V5.x Hardware Support Packages (HSPs) for the integrated PLC station types
• GSD/GSDML files for PROFIBUS and PROFINET slave configurations
• FB/FC libraries for NC variable access (NC-VAR-Selector, NCK interface blocks)
• HMI ProTool/Pro project templates
• PCIN transfer utility

The Toolbox is sold as a separately orderable item under Siemens part numbers that vary by software version:

Installation procedure:

1. Insert the Toolbox DVD or mount the ISO image in the PG/PC.
2. Close all STEP 7 components (SIMATIC Manager, HW Config, Symbol Editor).
3. Launch Setup.exe from the toolbox root directory.
4. Select "Hardware Support Packages" and choose the HSP matching the controller (e.g., 840D Powerline NCU 561.x, 571.x, or 572.x for 840D sl).
5. Restart STEP 7 and confirm the new station appears under SIMATIC 300 > Sinumerik in the HW Config catalog.

Once the HSP is installed, the standard "Upload Station to PG" path recognizes the controller. The complete PLC program and HW Config can be archived to a STEP 7 project on the PG.

Connecting via MPI PC Adapter (6ES7972-0CA23-0XA0)

The MPI PC Adapter is the conventional interface for connecting a PG/PC running STEP 7 V5.5 to a Sinumerik 840D Powerline. The default parameters are:

Set these via STEP 7 > Options > Set PG/PC Interface. Select "PC Adapter (MPI)" and configure accordingly. Use Accessible Nodes (PLC > Accessible Nodes) to verify connectivity before attempting a full upload.

For higher baud rates or PROFIBUS DP communication, the 840D Powerline and 840D sl expose a PROFIBUS interface on the X136 connector of the NCU. Communication interfaces on 840D sl support MPI, PROFIBUS, and industrial Ethernet (TCP/IP) at significantly higher baud rates than the legacy MPI path, but require a Toolbox GSD file to map the NCU station.

Accessible Nodes Workaround (Blocks-Only Upload)

If the Toolbox is unavailable but a PLC backup is urgently required, STEP 7 V5.5 supports a partial upload through the Accessible Nodes view:

1. In STEP 7, open PLC > Accessible Nodes.
2. Wait for the controller to appear with MPI address 2.
3. Select the station, then choose PLC > Upload Station to PG.
4. STEP 7 prompts: "Do you want to upload the station configuration?" Choose No.
5. STEP 7 uploads only the blocks (OB, FB, FC, DB, SDB, SFB, SFC) without the HW Config.

This produces an incomplete project — the HW Config shows as empty — but the program logic is preserved. The HW Config can be reconstructed manually by inserting an S7-300 station with the correct CPU (CPU 317-2 DP for 840D Powerline or CPU 319-3 PN/DP for 840D sl) and downloading the configuration to re-establish the link.

HMI Series Startup Backup Procedure (Operator-Level Full Backup)

The HMI-integrated series startup function is the recommended method for capturing a complete backup without STEP 7 Toolbox dependencies. It produces an archive containing NC data, PLC program, HMI configuration, and drive parameters.

Procedure for HMI Advanced (840D Powerline + PCU50)

1. Access the operator panel and navigate to the Service menu. The default path on HMI Advanced is Start > Commissioning > Series Startup.
2. Enter the service-level password when prompted. The active password is configured by the machine builder. If unknown, request it from the OEM; do not guess, as failed attempts may lock the access level.
3. Select "Create Series Commissioning Archive" or "Series Startup" (text varies by SW version).
4. Choose the archive scope: NC, PLC, Drives, HMI, or "All".
5. Select target media: Hard Disk (HMI), USB, or floppy (if equipped).
6. Confirm. The system writes files with extensions .arc (NC), .zip or .bkp (PLC backup), and .ini (configuration).

Typical output file naming on PCU50 hard disk under D:\dh\arc.dir or E:\dh\arc.dir:

• NC.arc — NC data and machine parameters
• PLC.arc — compressed PLC backup archive containing the STEP 7 project
• HMI.arc — HMI configuration (ProTool/Pro runtime)

To extract the PLC backup from the PLC.arc archive, copy it to a PG/PC and decompress it using WinRAR or 7-Zip. The extracted structure contains the STEP 7 project (S7 project as .zip or uncompressed .s7p) and the hardware configuration as separate files.

Procedure for Sinumerik Operate (840D sl)

1. Press the <Menu> key on the operator panel.
2. Navigate to Commissioning > Series Commissioning.
3. Enter the access level (password).
4. Select "Create Series Commissioning Archive".
5. Choose the directory and confirm.

File Transfer via PCIN and Removable Media

PCIN is the legacy Siemens tool for serial file transfer between a PG/PC and the Sinumerik HMI/NCU. It supports:

• Serial (RS-232) transfer at 19200 to 115200 baud
• File types: NC programs (.mpf, .spf), tool lists, R parameters, compensation data
• Bidirectional transfer (send and receive)

PCIN is bundled with the Sinumerik Toolbox DVD or can be downloaded from the official Siemens support portal. Launch with default parameters:

COM1: 19200 baud, 8 data bits, no parity, 1 stop bit
Protocol: Xon/Xoff

Procedure:

1. Connect a null-modem RS-232 cable between PG/PC (COM1) and the PCU50 COM1 port.
2. Start PCIN on the PG.
3. On the HMI, navigate to Services > Data Transfer and select "RS-232".
4. From PCIN, choose Send File / Receive File. Match the direction.
5. Monitor progress in the PCIN status window.

For large backups, USB transfer is faster. Most PCU50 systems expose a USB 1.1/2.0 port on the front panel. Mount a FAT32-formatted USB stick, copy the archive directory to it, then transfer to the PG. Avoid NTFS or exFAT — the HMI's USB driver only reliably mounts FAT32.

Network-Based Backup (TCP/IP on 840D sl)

The 840D sl exposes an Ethernet interface on the PCU. Use this for large backups when a network drop is available:

1. Configure the PCU50/PCU50.3 IP address via Services > Network or via the Windows XP Embedded control panel (PCU50 only).
2. Establish a Windows share on the PCU or use FTP/SCP if the controller firmware supports it.
3. Map the share as a network drive on the PG and copy D:\dh\arc.dir contents.

The 840D Powerline PCU50 supports standard SMB/CIFS file sharing once the network is configured. The 840D sl with PCU50.3 adds WebServices-based backup endpoints accessible via the Sinumerik Operate interface. Refer to the official Sinumerik 840D sl programming and operating documentation for TCP/IP parameter details.

Firmware and Software Version Compatibility

Version compatibility is the second most common source of upload failures after a missing toolbox. The relationship between controller SW version, toolbox version, and STEP 7 version is:

To read the controller's installed SW version on the HMI, navigate to Diagnostics > Service/Version or Commissioning > Version. The displayed SW string (e.g., "SW 6.4 HF 12") must match the toolbox version installed in STEP 7. Mismatches produce "incompatible SDB" alarms on download and silent corruption on upload.

Verification and Commissioning Checks

After installing the toolbox and re-attempting the upload, verify success with the following checks:

1. Open the uploaded STEP 7 project. Confirm HW Config shows the Sinumerik station with the correct NCU and PLC submodule types.
2. Cross-reference the program block list (OB1, OB40, OB82, OB100, OB121, OB122) against the controller's online view (PLC > Compare Blocks).
3. Verify the PLC diagnostic buffer shows "Cold restart completed" without "incompatible SDB" entries.
4. Test round-trip: download the uploaded project to the controller, monitor for "STOP -> RUN" transition without alarms.
5. Compare block checksums (CRC) using PLC > Compare Blocks Online/Offline.
6. Verify the FB/FC library is present in the project and that no unresolved symbol references remain.

Troubleshooting Matrix

Safety and Operational Notes

Per the official Siemens product support portal safety guidance for Sinumerik controllers, observe the following when performing backup and restore operations:

• Place the machine in a safe state (axes stopped, drives disabled) before any series startup or archive write operation.
• Ensure uninterrupted power to the PCU during a series startup archive write — a power loss can corrupt the HMI file system.
• Verify backups on a separate PG/PC before relying on them; never consider a backup valid until the round-trip (restore to identical hardware) has been tested.
• Do not share or disclose the active service password; it grants full read/write access to NC, PLC, and drives data.

FAQ