Restoring SIMOREG DC-MASTER Parameters After P051=21 Factory

Problem Overview

A SIMOREG DC-MASTER 6RA70/6RA80 series drive has been returned to factory defaults and the engineering team must determine exactly what was wiped, what is still salvageable, and how to rebuild the application dataset. Typical root cause is an operator or commissioning engineer executing P051 = 21 from the PMU (Parameter Menu Unit) keypad, DriveMonitor, or PROFIBUS/PROFINET interface without first archiving the dataset. Once this command is sent, the CUD1 parameter set is overwritten with Siemens defaults. The technology board (T400 / CB24 / SIMOLINK board, depending on firmware generation) holds a separate, independent parameter set that is unaffected by P051 = 21.

Three immediate questions follow any factory-reset event:

1. Which parameter image was lost — CUD1 only, T400 only, or both?
2. Can the old values be retrieved, either from on-drive backup, a DriveMonitor file, or a PLC archive?
3. Does the technology software (S00 technology option on T400) require the PIN to be re-entered after the reset?

Affected Components: CUD1 vs. T400 Architecture

The SIMOREG DC-MASTER is a multi-processor converter. The two functional blocks most often confused during a reset are:

Why P051 = 21 Only Resets CUD1

Parameter P051 is the parameter-access enable / function selector on the CUD1. The relevant values are:

Because the T400 technology board runs its own firmware image and stores its parameters in a separate EEPROM / flash region, P051 = 21 cannot reach it. T400 reset is performed either through DriveMonitor under the T400 node, or — in older 6RA70 with firmware < 3.10 — through a dedicated technology commissioning tool. After the reset, the drive must be re-powered (24 V control supply off/on) for the new defaults to become active in the CUD1.

Pre-Reset Best Practice: DriveMonitor Backup

Before any commissioning activity, the DriveMonitor offline image should be saved to the engineering PC. DriveMonitor stores a complete, per-drive parameter archive (file extension *.dnx or *.par, depending on version) including the CUD1 dataset, the T400 dataset, and — where SIMOTION SCOUT integration is active — the technology project.

1. Open DriveMonitor and connect to the drive (RS232 to PMU-X300, or PROFIBUS/PROFINET to the bus address).
2. Right-click the drive node and select Read All Parameters.
3. From the File menu, choose Save Parameter Set As… and store the file with a project number and date stamp.
4. If a T400 technology board is fitted, expand the T400 sub-node and repeat the read/save sequence — DriveMonitor stores T400 parameters in a separate block within the same archive.
5. Verify the file size on disk: a populated CUD1 + T400 archive is normally 200 – 600 kB; a near-empty file (< 30 kB) is a sign the read failed.

Reading Parameters from an S7-300 via PROFIBUS PKW

If no DriveMonitor backup exists, every value that the PLC has ever written to the drive is a candidate for re-derivation. The SIMOREG 6RA70/6RA80 supports the PROFIBUS DP-V1 PKW mechanism (Parameter-Kennung-Wert) inside the standard PPO type 1 / PPO type 5 telegram. The PKW section is 8 bytes: ID, index, parameter number, subindex, value (low word / high word). The PLC reads the current value from the drive, the application program re-applies the engineering setpoints, and the operator re-commissions the closed-loop regulators.

PKW Read from STEP 7 (S7-300, SFC 14 / SFC 58 / SFC 59)

The recommended sequence in a STEP 7 / TIA Portal S7-300 project is:

1. Confirm the drive's PROFIBUS node address matches the HW Config (default 3 for CUD1).
2. In OB1, call SFC 14 (DPRD_DAT) to read the PZD section (process data) and SFC 58 (READ_PKW) or a standard PKW block to read the PKW section.
3. For each parameter to be read, populate the request with: PKE = 0x6xx (read request) + parameter number, IND = subindex + index byte, then call SFC 58 on the configured I/O address.
4. Store the returned value in a DB for the commissioning engineer to inspect.

Example request structure (read parameter P100, subindex 0):

PKE: 0x6100  |  0x0064  (request, parameter number 100 = 0x0064)
IND: 0x0000  |  0x0000  (subindex 0, index high byte 0)
PWE: 0x0000 0000         (value field, not used on request)

Example response (drive answers with current value 0x4A3F = 19007):

PKE: 0x4100  |  0x0064  (response, parameter 100)
IND: 0x0000  |  0x0000
PWE: 0x0000 4A3F         (current parameter value = 19007 decimal)

A pragmatic recovery strategy: in the S7-300 program, search for all drive parameter write operations (cross-reference against function blocks such as FB 100 / FB 250 / user PKW write blocks) and re-execute them on the now-factory-default drive. This restores the application setpoint image even though the drive's internal copy is gone.

Re-Building the CUD1 Parameter Image Without a Backup

When neither a DriveMonitor file nor a PLC re-write set exists, the values must be re-engineered. Use the following anchors:

After loading the power section data, run the autotune sequences in this order: armature current (P051 = 25), speed / EMF (P051 = 26), field current (P051 = 27), and — if a T400 technology board is fitted — friction / moment of inertia compensation (P051 = 28). Wait for each to complete before starting the next; do not abort.

S00 Technology Software and the PIN Question

The T400 technology board runs a compiled technology image (S00 free function blocks, or the S120 / S150 / winder technology packages). The compiled image is stored on the T400 itself — not on the CUD1 — and is therefore untouched by P051 = 21. No PIN number is required to re-execute the S00 technology software; the PIN is associated with the technology function library licence, not with the S00 executable.

However, parameter n978 on the CUD1 enables or disables the PIN-protected features on the basic drive (for example, write-protection of commissioned parameter sets in some firmware versions). After a P051 = 21 reset, n978 returns to its factory default, which is normally 0 (PIN disabled). The user is free to re-enter the PIN at any time; the procedure is described in the operating instructions and uses the operator panel under Parameters > Security > PIN.

Identifying Firmware State After Reset

Always record the firmware version before and after a reset, so that any future firmware mismatch is traceable. The CUD1 firmware version is read in:

• r060 — software version of the CUD1 firmware (numeric, e.g. 3.14.2)
• r065 — software version of the bootstrap loader / boot sector

These two indices survive a P051 = 21 reset; they are read-only, factory-burned into the flash. The latest released firmware for the 6RA70 family is published on the Siemens support portal; a reference list of versions is documented in the C98130-A1256 and C98130-A7040 SIMOREG DC-MASTER operating instructions.

Reference manuals:

• SIMOREG DC-MASTER Operating Instructions (C98130-A1256)
• SIMOREG DC-MASTER Control Module (C98130-A7040)

Step-by-Step Recovery Workflow

1. Document the event. Note the time of reset, the person who executed it, and the PMU display at the moment of the command. Photograph the PMU.
2. Read r060 / r065 on the CUD1 and the T400 technology board. Save the values to the project log.
3. Check for a DriveMonitor archive. If one exists on the engineering PC, file server, or project document repository, load it back to the drive via DriveMonitor (File > Load Parameter Set to Drive) and verify with Compare with PG / PC.
4. If no DriveMonitor archive exists, search the STEP 7 project for PKW write blocks and re-execute them from the S7-300. Verify each parameter response in the DB.
5. If no PLC writes exist, re-engineer the parameter set using the application documentation and run P051 = 25 / 26 / 27 autotune in the safe-off state.
6. Reload the T400 technology image (S00 / S120 / S150) only if the T400 itself was reset. The S00 image is independent of the CUD1 reset.
7. Verify the S00 PIN state with parameter n978. Re-enter the PIN only if the application requires write-protection of the commissioned set.
8. Power-cycle the 24 V control supply and the power section; wait for the CUD1 to complete its self-test (PMU displays a number then shows the operating state).
9. Take a fresh DriveMonitor backup and store it under the project number. This becomes the new recovery anchor.

Verification Checklist Before Re-Energising the Drive

Field-Commissioning Notes and Common Pitfalls

• P051 = 21 vs. P051 = 30. Use P051 = 30 if the bus address must survive the reset. P051 = 21 wipes the bus address as well, which will drop the PLC into a station-failure state.
• Power-cycle discipline. The factory defaults are only latched after a control-electronics off/on cycle. A re-power of the 24 V auxiliaries is mandatory before any new values become visible.
• PMU edits are not the same as DriveMonitor edits. Some parameters require a confirm step (for example P051 itself, P918, P927) — read the response prompt on the PMU.
• Write-protection (n978 / n979). After a reset, write-protection is disabled. If the site has a write-protection policy, set n978 to the project PIN and verify that subsequent parameter changes are blocked without PIN entry.
• Technology option (S00) re-binding. The compiled S00 image is bound to a specific T400 module at build time. If the T400 module has been physically replaced, the S00 image must be re-bound to the new module; the CUD1 PIN does not play a part in this re-binding.
• PROFIBUS connector grounding. After a reset, bus failures are occasionally traced to a connector that was disturbed during the PMU session. Verify shield continuity before assuming a parameter error.
• PLC re-write race. When the S7-300 re-writes parameters on startup, the drive may not have completed its boot sequence. Insert a startup delay (typ. 3 – 5 s after the drive signals "ready") before issuing the first PKW write.

Troubleshooting Matrix

FAQ