SIMOTION D4x5-2 CF Card Replacement: Boot, Licensing & Recovery

Problem Statement: SIMOTION D4x5-2 with Damaged or Missing CF Card

The SIMOTION D4x5-2 motion controller family (type designations 6AU1 4xx-..., covering D425-2, D435-2, D445-2 and D455-2) is designed to run from a CompactFlash (CF) card that stores the firmware image, the SIMOTION project (compiled technology objects, programs, configuration data, axis data), persistent runtime variables, and the license keys for the loaded Technology Packages. The controller cannot complete its boot sequence and therefore cannot operate without a valid CF card present in the slot on the front panel.

This article documents the field-proven replacement procedure for a damaged or unreadable CF card, the requirements a replacement card must satisfy, the supported methods for re-binding license keys, the risks of removing the card while the controller is in RUN, and the migration path to the SIMATIC Drive Controller for users who plan to retire the SIMOTION D4x5-2 platform.

Why the CF Card Is Mandatory on D4x5-2

The CF card is not a peripheral storage device on the D4x5-2; it is the controller's mass storage and the boot device. The boot ROM on the D4x5-2 looks for a partition on the card that contains a valid SIMOTION boot sector. If that boot sector is missing, corrupted or unreadable, the controller halts in stop state. The card must also contain a firmware partition that the boot ROM hands off to once the boot sector passes control.

If any of these regions is unreadable, the controller reports a corresponding boot fault and remains in STOP with the SF (red) LED on. The yellow / green status LEDs follow the standard SIMOTION startup sequence documented in the SIMOTION D4x5-2 system manual (entry 109480700).

Symptoms of a Damaged CF Card

Before replacing, confirm that the symptom is actually a card fault rather than a controller, firmware, or project fault. Typical CF-card failure symptoms include:

• Controller does not complete boot; SF LED remains on steady after power-up
• Boot process stops with one of the diagnostic messages referencing the card filesystem (see FAQ entry 31045047 on CF card information)
• Web server / SIMOTION IT diagnostics cannot mount the card volume
• Card is mechanically damaged (bent pins, cracked housing) — replace immediately
• Intermittent filesystem errors after a controlled shutdown was interrupted (for example, supply voltage removed during a write operation)

Before any replacement, save the diagnostic buffer (Diagnostics > Diagnostics Buffer in SIMOTION Scout) if possible, and capture the active project with a project download to archive. If the card is still partially readable, take an offline sector-level image with a CF-card reader on a Linux or Windows PC and store the image as a backup before any further operations on the card.

LED State Reference During Card-Related Boot Faults

The 2 Hz SF flash in combination with RDY green is the classic signature of a missing license on a successfully booted card, which is one of the most common issues immediately after a CF-card replacement.

Replacement Procedure

Prerequisites

1. Replacement CF card. Recommended capacity: 2 GB or larger, industrial-grade CompactFlash. Siemens-qualified cards are listed in the SIMOTION D4x5-2 manual and in FAQ 31045047. Consumer-grade cards are not recommended because of wear-levelling and write-throughput mismatches.
2. SIMOTION Scout (or SCOUT TIA) installed on an engineering PC, version matching the firmware on the controller or the version of the project being deployed.
3. Original project archive (zipped SIMOTION project, .zip created via Project > Archive) on the engineering PC.
4. Firmware matching the controller type and CPU version, downloaded from Siemens Product Support as a *.zip. Do not unpack it manually.
5. USB or Ethernet cable for PG/PC connection to the D4x5-2 service interface (X120 / X130 / X127 / X150 depending on variant).
6. If the controller carries licensed Technology Packages: the license key file (.lic) or access to Siemens Product Support for license re-mapping.

Step-by-Step: Prepare a Replacement Card with SIMOTION Scout

1. Power down the D4x5-2 and remove the defective CF card from the slot.
2. Insert the replacement CF card into a USB / IDE CF reader on the engineering PC.
3. Start SIMOTION Scout. From the project tree, select the controller and open Target system > CF card > Prepare CF card. Scout formats the card, writes the boot sector, and prepares the firmware partition.
4. When prompted, select the firmware matching the original installation. Firmware is delivered as a *.zip file from support.industry.siemens.com; do not unpack it manually.
5. Confirm the boot sector write. Scout reports success once the boot sector is in place.
6. Insert the prepared card into the D4x5-2 slot. Power up the controller.
7. Wait for the boot sequence to complete (yellow RDY LED transitions to steady green). If the controller reports a missing project, perform the project download in step 8.
8. From the engineering PC, connect to the controller in SIMOTION Scout (Target system > Connect to target system), then Target system > Download > Download project to target system. Include the hardware configuration and the technology packages.
9. Cycle the controller power to activate the downloaded project.
10. If Technology Package licenses are missing after the download, perform the license re-mapping procedure described later in this article.

What to Do If Scout Refuses the Card

SIMOTION Scout validates the card model and capacity against a known-good list. If the chosen card is rejected:

• Confirm the card capacity is within the supported range (typically 2 GB to 8 GB industrial CF; the controller does not support very large modern CF cards due to the card controller interface).
• Confirm the card is a true industrial-grade CompactFlash with a guaranteed write-endurance rating (look for the manufacturer's industrial / fixed-disk SKU, not the consumer line).
• Retry with a different CF card reader; some USB readers do not negotiate the CF interface correctly and present the card as a removable disk with a corrupted partition table.

License Re-Mapping Procedure

SIMOTION licenses are bound to the CF card's serial number. A new card means new license keys must be issued. There is no way to copy a license from one card to another with SIMOTION tools; the re-mapping has to be performed by Siemens.

1. Open a support request via Siemens Product Support. Provide the controller's serial number, the original order numbers for each Technology Package license, and the serial number of the new CF card.
2. Siemens support generates a license assignment for the new card and provides a *.lic file (or, for Web License Manager activations, a license ticket).
3. Load the new license onto the D4x5-2 through SIMOTION Scout: Target system > Licensing > License assignment, or via the SIMOTION IT web server with administrator rights.
4. Verify in the licensing overview that all Technology Packages (e.g. TO Axis, TO Cam, TO Synchronous Operation) show Licensed.

For plants with multiple SIMOTION D4x5-2 controllers, license re-mapping can be batched through Siemens support. Each controller requires its own license bundle; licenses are not interchangeable between controllers. Keep the license evidence (COA, license key certificate) on file so the re-mapping request can be processed quickly.

Hot-Swap Behaviour and Risk Analysis

A common field question is: what happens if the CF card is removed while the controller is in RUN?

Answer: the controller stops the machine and transitions to a stop / error state. Specifically:

• The runtime detects the loss of the active filesystem partition within milliseconds.
• All TO axes are commanded to stop with the configured stop response (typically STOP with ramp; see axis configuration in the project).
• The diagnostic buffer records a card-loss entry; the SF LED turns on.
• After re-inserting the card and powering up, the controller may require a project re-download if the persistent area is detected as inconsistent.

More importantly, the card itself is at risk. Any flash-based storage can suffer filesystem corruption if power is removed during a write operation. The CF cards used in D4x5-2 are industrial-grade, but the write patterns during normal operation — especially persistentMemory calls — are not protected by a write-cache barrier that survives power removal. Pulling the card under power is, in practice, the leading cause of card failure in installed base.

Persistent Data and Encoder Offsets

The persistentMemory system function is the standard mechanism for saving encoder offsets, calibration values, and other data that must survive a power cycle. The data is written to a file on the CF card; without the card (or with a damaged card), this file is unreadable and the runtime falls back to the values compiled into the project.

To recover persistent data after a card replacement, two options exist:

1. If the controller's online connection still works: read out the persistent area via the SIMOTION IT web server (Diagnostics > Persistent data) before powering down, then re-inject it after the new card is in place.
2. If the original card is partially readable: mount it on a Linux PC with a CF reader, copy the persistent file, and inject it through Scout.

If neither path is available, encoder offsets must be re-established by running the machine's homing procedure. Plan for at least one to two hours of re-commissioning per machine axis when persistent data is lost.

While recovering, observe the rule that persistentMemory writes are issued only at controlled points in the program (typically end-of-cycle or end-of-batch), and only after the previous call has completed. Inspect the project's ret_persistentData / ret_persistentMemory error handling to verify the controller is not silently losing persistent writes on each cycle.

Communication and Fieldbus Considerations

The D4x5-2 uses PROFINET IO and PROFIBUS DP for distributed I/O, and either can be affected during a card swap:

• PROFINET IO: the controller's PROFINET device name and IP address are stored on the CF card. After replacing the card, the PROFINET name must be re-assigned via the SIMOTION Scout or via the PROFINET commissioning tool. PROFINET IO devices will report station failure during the swap window.
• PROFIBUS DP: the DP slave configuration is part of the project on the card. Once the project is downloaded to the new card, the DP bus comes back automatically; existing slave addresses do not require re-assignment.
• Drive telemetry: SINAMICS S120 drives configured over PROFINET or PROFIBUS will report F08501 (life sign monitoring) during the card swap. Clear the fault at the drive side after the controller returns to RUN.

For plants with hot-standby or redundant SIMOTION D controllers, the swap procedure is identical but the secondary controller must be confirmed as master before any card operation, otherwise the master will record a card-loss event in its diagnostic buffer.

Migration Path: SIMOTION D4x5-2 to SIMATIC Drive Controller

Plants that are still on D4x5-2 and planning a major upgrade should consider migrating to the SIMATIC Drive Controller (DC). The migration is supported by a documented comparison and procedure: Information for users changing from SIMOTION D4x5-2.

Migration is not a card swap. It requires re-implementation in TIA Portal, including the technology objects. For brownfield applications where the controller hardware must be replaced but the machine mechanics remain, Siemens provides migration tooling; consult the application example linked above for the mapping tables between Scout axis configuration and TIA Portal technology objects.

Verification Checklist After Card Replacement

1. Controller powers up to RUN; SF LED off, RDY LED green steady.
2. All configured Technology Objects (axes, cams, synchronous groups) are present and report OK status in SCOUT / TIA Portal.
3. License overview shows Licensed for every Technology Package used by the project.
4. Persistent data is restored and matches the values prior to the failure (compare via SIMOTION IT web server or program variable read).
5. Diagnostic buffer is clear of card-related entries from the new boot sequence.
6. PROFINET IO devices are reachable; station names and IP addresses are correct.
7. PROFIBUS DP slaves are online with no configuration mismatch.
8. Drive side faults (e.g. F08501 on SINAMICS S120) are acknowledged.
9. Run the machine's standard reference motion profile (a slow reference move) and confirm tracking error stays within configured limits.
10. If safety functions are configured: perform the safety acceptance test per the machine's safety plan before returning the machine to production.

Troubleshooting Matrix

Edge Cases and Field-Proven Caveats

• Mixed firmware / Scout version: if the Scout version on the engineering PC is older than the firmware on the controller, the card preparation may complete but the firmware on the new card will not match. Always match Scout version and firmware version per the compatibility matrix in the SIMOTION SCOUT manual, Chapter 12 Download (entry 109767621).
• Multi-language project files: the project archive may contain localized alarm texts in multiple languages. After a card swap, confirm the active language is still selected, otherwise some operators will see a different alarm text than before.
• Card reader driver issues: some Windows 10 / 11 builds incorrectly mount CF cards as read-only when the card's filesystem was previously written by Scout. Re-inserting the card or using a different reader resolves it.
• Battery-backed RTC: the D4x5-2 has a buffered real-time clock. The card swap does not affect the RTC, but if the buffer battery is also dead, expect the controller to report a time/date fault on next boot. Replace the battery before returning the machine to production if the time/date is used for alarm timestamping.
• Slot wear: the CF slot on a D4x5-2 has a finite insertion count. Repeated card swaps (more than a few dozen) can wear the connector pins and cause intermittent card detection. If the slot is suspected, route the diagnosis through Siemens support; the slot is a serviceable part on most D4x5-2 variants.

FAQ