Migrating SIMOTION D425 to D425-2 DP: SCOUT Project Conversion

Overview

SIMOTION D425 (MLFB 6AU1425-0AA00-0AA0) and SIMOTION D425-2 DP (MLFB 6AU1425-2AA00-0AA0) are members of the SIMOTION D4x5 / D4x5-2 motion-controller family. Both run the SIMOTION V4.3 runtime and use SIMOTION SCOUT V4.3 as the engineering tool, but they differ in on-board I/O, drive-interface count, and fieldbus topology. When inventory forces a swap of a D425 for a D425-2 DP, the existing SCOUT project must be updated to the new device type; otherwise the downloader rejects the target with:

Error: D425 - Not possible to establish connection from device of type 'D425 V4.3' to hardware of type 'D425-2 V4.3'

This reference covers the supported module-replacement workflow in HW Config, the typical follow-up errors related to the X142 on-board I/O and the optional CBE30 PROFINET board, and the diagnostic-buffer steps required to commission the converted project. The official Siemens migration procedure is documented in the SIMOTION D4x5-2 Migration Manual (PDF, 77498350), which states that the change from D4x5 to D4x5-2 is performed via a module replacement in HW Config, similar to a D425 to D435 upgrade.

Hardware Identification

The X142 connector on D425-2 exposes an additional digital I/O group that is not modeled on the original D425 rack. The HW Config in SCOUT for the D425 has no slot for X142, so on a module replacement the new D425-2 slot becomes visible and is left empty or unconfigured unless the engineer explicitly assigns it. This is the single most common source of post-migration errors. For background on the platform differences, see the TIA Portal documentation page Information for users changing from SIMOTION D4x5-2.

Prerequisites

1. SIMOTION SCOUT V4.3 SPx (or TIA Portal V15 with SCOUT add-in) installed on the engineering station.
2. The original SCOUT project (D425 V4.3) backed up to a known directory; the .ssp archive plus the working directory are both required.
3. SCOUT project consistency state known — confirm that the source project compiles cleanly before any migration work.
4. Read/write access to the D425-2 DP target over PROFIBUS DP or Ethernet (PROFINET via CBE30 if used).
5. Firmware version of the new CPU confirmed as V4.3, readable via accessible nodes, the device label, or the CF-card sticker.
6. If the existing project uses a CBE30 PROFINET option board, the CBE30 must be physically installed in the D425-2 before download, and the SCOUT project must be configured to match the cabinet reality.
7. Password file for the project (if password-protected) accessible; the password travels with the SCOUT project, not the CPU.

Module Replacement in HW Config

The supported Siemens migration path is a module replacement in the SCOUT HW Config, identical to the procedure used when stepping from a D425 to a D435. Per the official D4x5-2 Migration PDF, the change is performed by selecting "Change Device" on the CPU slot and pointing it at the D425-2 DP variant. SCOUT then automatically rewrites the device identity in the project tree.

Step 1 — Open the SCOUT Project and HW Config

1. Start SIMOTION SCOUT V4.3.
2. Open the existing D425 project (.ssp archive or live project).
3. In the project navigator, right-click the SIMOTION device and select Open HW Config.

Step 2 — Initiate Device Change

1. In HW Config, right-click the CPU slot (the SIMOTION D425 entry at slot 0 or the slot corresponding to the controller in the rack).
2. Select Change Device... (German: Gerät tauschen).
3. In the device catalog, navigate to SIMOTION > D4x5-2 > D425-2 DP.
4. Confirm the MLFB 6AU1425-2AA00-0AA0 and firmware V4.3 are selected.
5. Click OK to apply the change.

Step 3 — Save HW Config

1. Save HW Config (Ctrl+S). SCOUT automatically propagates the device type change into the SIMOTION project tree.
2. HW Config now displays the new D425-2 rack, including the X142 on-board I/O slot, which the previous D425 rack did not contain.
3. Close HW Config and return to the SCOUT project navigator. The device entry must now read "SIMOTION D425-2 DP V4.3." If it still reads D425, the change did not propagate — repeat Step 2.

Compile, Consistency Check, and Download

After the device change, the project must be recompiled offline and a consistency check performed before a download is attempted. If the project is downloaded without a recompile, the SCOUT downloader reads the old D425 V4.3 as the source type and the new D425-2 V4.3 as the target type — the precise condition that triggers the connection error.

Offline Recompile Procedure

1. Right-click the SIMOTION D425-2 DP in the project tree.
2. Select Compile and check consistency (menu: Target system > Compile and check consistency).
3. Inspect the messages window for I/O, address, and topology errors.
4. Resolve any reported discrepancies before continuing.

Download to Target Device

1. Right-click the D425-2 DP and select Download to target device.
2. Choose the appropriate PG/PC interface (PROFIBUS DP or Ethernet, depending on cabling).
3. If the firmware V4.3 mismatch dialog appears (for example, a non-matching Service Pack), follow the prompt to perform a firmware download or RAM-to-Flash update before transferring the project.
4. Confirm the download. SCOUT will write the configuration and program to the CF card.

Common Error: Connection Type Mismatch

Symptom: After selecting "Download to target device," SCOUT returns:

Not possible to establish connection from device of type 'D425 V4.3' to hardware of type 'D425-2 V4.3'

Root Cause: The SCOUT project navigator still has the D425 V4.3 device type cached, or the project was not recompiled after the HW Config device change. The project tree caches the source device identity separately from the HW Config CPU slot, so a save in HW Config alone is not enough; the project-level compile is required to propagate the new identity into the downloader context.

Resolution:

1. In the SCOUT project navigator, right-click the SIMOTION device and verify the displayed device type reads "SIMOTION D425-2 DP V4.3."
2. If the navigator still shows D425, the HW Config change did not propagate. Repeat the "Change Device" operation in HW Config and save the project.
3. Right-click the D425-2 DP and run Compile and check consistency again. Wait for green status.
4. Retry the download.

Common Error: X142 I/O Discrepancy

Symptom: After the device change, the consistency check or download reports errors referencing X142 I/O addresses. The original D425 HW Config has no X142 slot, but the D425-2 rack exposes one.

Root Cause: The HW Config slot for the D425-2 on-board I/O (X142) is left in its default unconfigured state. SCOUT may report "address gap" or "I/O not assigned" warnings, and the diagnostic buffer at runtime shows IO configuration errors referencing the X142 address area.

Resolution:

1. Open HW Config for the D425-2.
2. Double-click the X142 slot. Decide between the two options:

• Configure X142: assign input bytes, output bytes, and analog ranges to match the field wiring (digital inputs at I0..I1, digital outputs at Q0..Q0, analog input at PIW, analog output at PQW, per the SIMOTION D4x5-2 manual).
• Remove X142 from rack: if X142 is not wired in this machine, delete the slot to silence the warning. SCOUT allows deletion of unused on-board I/O.

1. Save HW Config and recompile the project.

CBE30 Option Board Considerations

The SIMOTION D4x5-2 family supports the CBE30 PROFINET option board for Ethernet-based fieldbus. The original D425 may or may not have had a CBE30 fitted; the D425-2 DP, by default, exposes PROFIBUS DP and uses CBE30 only if installed. The four possible scenarios are listed below.

If the project tree contains a CBE30 device and the option board is not physically present on the D425-2, the consistency check will fail with a slot mismatch. The error will reference a CBE30 slot that SCOUT cannot reach. In that case, open HW Config, right-click the CBE30 slot, and either delete it or replace it with the correct option board part number.

Diagnostic Buffer Analysis

After every download attempt, always read the diagnostic buffer of the new D425-2 DP. The diagnostic buffer is the definitive record of what the firmware actually saw during the load operation. Common entries and their meanings are summarized below.

To open the diagnostic buffer in SCOUT: right-click the D425-2 DP > Target system > Diagnostics > Diagnostic buffer. Read the most recent entries first; older entries are historical and can be ignored once the current issue is resolved.

Verification and Commissioning

1. After successful download, click Copy RAM to ROM on the target to persist the project to the CF card.
2. Perform an Online > Compare between the SCOUT project on the engineering station and the running target. The diff must show zero differences.
3. Read the diagnostic buffer; confirm no I/O faults are present.
4. Switch the target to RUN. The SIMOTION D425-2 DP must transition to RUN within seconds; any STOP-to-RUN stall indicates a technology-object configuration mismatch, often in the TO configuration (axes, cams, encoders).
5. From the SCOUT axis control panel, enable each axis and verify the position controller, encoder feedback, and drive enable are healthy.
6. Run a slow-speed test on the motion axes to confirm DRIVE-CLiQ topology and the new CPU's PROFINET or PROFIBUS communication are stable.
7. Capture a fresh project backup of the commissioned D425-2 configuration to the engineering file server.

Field-Proven Caveats

• Technology objects (TO): The TO configuration is hardware-agnostic at the SCOUT level, but axis assignments to specific drives (for example, SINAMICS S120 via DRIVE-CLiQ) reference drive objects. Verify the DO names in the new D425-2 project match the actual topology.
• Symbolic I/O references: If the program reads or writes to %I or %Q addresses that were implicitly mapped to X142 on the new CPU, recompilation may flag them as unresolved. Either configure X142 with the matching addresses or refactor the program to use the external ET200 addresses that the original D425 used.
• CF card compatibility: D425-2 supports higher-capacity CF cards. If the original card is being re-used, verify its file system is clean; a mix of D425 and D425-2 boot files on the same card can cause boot loops. Format the card on the D425-2 before first use.
• Service Pack level: V4.3 covers multiple HF/SP releases. Mismatches between the SCOUT project SP level and the D425-2 firmware SP level will trigger a firmware download prompt on first connection. Accept and complete the firmware transfer before retrying the project download.
• Password protection: If the original project was password-protected, the password travels with the SCOUT project, not the CPU. Re-enter the password on first online connection to the D425-2.
• Drive object topology: After a D425 to D425-2 swap, the DO names in the project must match the cabinet reality. If a drive was renamed during commissioning, the migration does not rewrite the name; verify before axis enable.
• Watchdog and cycle time: D425-2 supports shorter servo cycles than the original D425. If the program relied on a specific IPO or servo clock, double-check the timing configuration in the project after the device change.

FAQ