SINUMERIK 840D PCU50.3 NCU Link Configuration Troubleshooting

1. Problem Overview

On a SINUMERIK 840D Power Line control retrofit or test-bench build, a PCU50.3 booted with HMI Advanced can fail to establish its expected direct link to the NCU. Instead of the legacy Operator Panel softkey area, the operator panel screen exposes an NCU Link entry pointing to an IP address. The PCU never completes startup communication with the NCU 572.4, even though point-to-point MPI on X122 and PROFIBUS on X101 both report healthy nodes from a manual scan with SIMATIC Manager.

This symptom is the classic fingerprint of a PCU that was previously configured for SINUMERIK Solution Line (SINUMERIK 840D sl) operation and was never converted back to the older Power Line personality. Power Line boot expects an MPI/PROFIBUS handshake to the NCU at a fixed baud rate and known node addresses; Solution Line boot expects an Ethernet TCP/IP handshake to an NCU link manager.

1.1 Affected Hardware and Software Stack

2. Root Cause Analysis

The mismatch has three contributing causes that must all be addressed.

2.1 PCU Personality Locked to Solution Line

HMI Advanced 07.05.02.00 contains both Power Line and Solution Line boot personalities. When the install media is for an 840D sl system, the installer configures:

• An Ethernet NCU Link softkey bound to a default IP (typically 192.168.214.1 on the NCU side, 192.168.214.240 on the PCU side for Solution Line defaults).
• Removal of the Power Line Operator Panel softkey (which historically displays NCK, PLC, and MMC node addresses).

The legacy Power Line Operator Panel softkey is the one that exposes the editable fields for:

2.2 No MPI/PROFIBUS Boot Channel Configured

Because the personality is Solution Line, HMI Advanced boot looks for the NCU over Ethernet first and times out. The healthy MPI scan you see when you manually launch SIMATIC Manager on the PCU proves the bus is electrically and parametrically correct — nodes 0, 2, and 3 are visible at X122, node 13 at X101 (PROFIBUS) for a factory-reset NCU 572.4. The system is therefore physically correct and is being held back by a software/personality mismatch only.

2.3 Unverified PLC Firmware Build on NCU 572.4

NCU module firmware 6FC5250-6BX30-5AH0 version 06.05.26 is an older Power Line build. This is consistent with the Power Line stack but is incompatible with HMI Advanced 08.x Solution Line personalities. If HMI Advanced was upgraded to a release expecting a Solution Line NCU, the system can show NCU Link as a fallback while it waits for a build it cannot find on the bus.

3. Preconditions for a Clean Power Line Restore

1. NCU 572.4 must boot cleanly with two green status LEDs (PF and PS or equivalent NCU indicators). Two-green is the Power Line NCK-ready state.
2. NCU must be factory reset (PLC stop + NCK reset to defaults) so that the bus addresses match the values in the table above.
3. PCU50.3 must have administrative access (Windows XP admin or equivalent local admin account).
4. Original Power Line install media for HMI Advanced 07.05.02.00 must be available (CD set or service pack image).
5. Valid license keys (CF card or hard-disk licensing) for HMI Advanced 07.05.02.00 must be present or restored.

4. Step-by-Step Restoration Procedure

Step 1 — Remove Solution Line NCU Link Configuration

On the PCU50.3, log into Windows XP with administrator rights and stop HMI Advanced from the Windows desktop or from Start > Programs > SINUMERIK > HMI > Exit HMI.

Open the registry editor and inspect the following keys. Remove or correct entries that point to an Ethernet NCU link:

Specifically, delete any REG_SZ value named NCULink_IP or NCUAddressEthernet. These are the values that make HMI Advanced render the "NCU Link" softkey with an IP field.

Step 2 — Restore Operator Panel Softkey

The Power Line operator panel configuration is loaded from:

A correct Power Line entry should look like:

[OperatorPanel]
BusType = MPI
BaudRate = 1500000
NCK_Address = 0
PLC_Address = 2
MMC_Address = 3

If the file is missing or has been overwritten with a Solution Line template, recreate it with the values above. Do not invent values; 1500000 (1.5 Mbaud) is the standard Power Line rate and matches the NCU 572.4 default.

Step 3 — Force HMI Advanced to Re-Select Power Line Personality

If a previous Solution Line install left traces, re-run the HMI Advanced installer from the Power Line media and choose PCU50 / Power Line as the target personality. The installer overwrites the boot personality flags in:

Ensure the value Personality is set to PowerLine. A value of SolutionLine means the installer was given the wrong media or the wrong option.

Step 4 — Validate MPI Node Assignments

From the PCU50.3, launch SIMATIC Manager and open Accessible Nodes on the MPI interface. Confirm that the scan reports nodes 0 (NCK), 2 (PLC), and 3 (MMC). If node 3 is missing, the MMC address in operator_panel.ini must be changed to match what is actually configured on the CP5611 / CP5613 MPI card in the PCU.

You can also inspect the MPI card configuration under Start > Settings > Control Panel > Set PG/PC Interface. The active access point must be S7ONLINE (STEP 7) -> CP5611.MPI or the equivalent PROFIBUS CP, and the "Own node address" field should read 3.

Step 5 — Re-enable HMI Advanced Boot Sequence

Restart the PCU50.3. The HMI Advanced splash screen should appear, followed by the Power Line start-up with the Operator Panel softkey visible and editable. If the NCU Link softkey still appears, return to Step 1 and verify that all NCULink_* registry values have been removed.

5. Verification Checklist

6. Power Line vs Solution Line Personality Reference

7. Common Alarms and What They Tell You

8. Hardware Validation — Independent of Personality

Before any software fix, prove the hardware is good. Two fast checks exist.

8.1 MPI Scan on X122

Connect an MPI cable between PCU50.3 CP5611 (or equivalent) port and NCU 572.4 X122. From SIMATIC Manager on the PCU, select Accessible Nodes with the MPI access point. Expected nodes: 0 (NCK), 2 (PLC), 3 (MMC). If only 0 and 2 appear, the PCU is not on the bus at 3 and the CP configuration must be fixed.

8.2 PROFIBUS Scan on X101

Connect a PROFIBUS cable between PCU50.3 PROFIBUS CP and NCU 572.4 X101. Expected node: 13 for a factory-reset NCU on PROFIBUS. If 13 is visible, the NCU PROFIBUS interface is alive and the bus parameters are correct.

9. PCU50 vs PCU50.3 — Practical Differences for This Scenario

The original PCU50 is a single-personality Power Line box. The PCU50.3 (introduced with the 840D sl era) is a dual-personality industrial PC: it can boot either Power Line or Solution Line, and the personality is selectable at install time. For a test bench that already has a working PCU50 (Power Line only), it is often simpler to use that PCU50 instead of trying to revert a PCU50.3.

If the PCU50.3 must be reused (because it is the only spare), the procedure in Section 4 above is the correct path. Manual references for the older PCU50 / MMC103 commissioning procedure apply to the PCU50.3 Power Line personality as well, but the screenshots in older manuals show the Operator Panel softkey because they pre-date the dual-personality build.

10. Related Configuration Files

11. Documentation References

• SINUMERIK 840D sl Operator Components Manual (PCU50.3 section)
• SINUMERIK 840D Commissioning Manual - NCK / PLC / Drive commissioning
• SINUMERIK HMI Advanced Programming Manual
• SINUMERIK 840D/840Di/810D Operator Panel Configuration

12. Quick Field Diagnostic Flow

1. Boot NCU 572.4. Confirm two steady green status LEDs.
2. From PCU, scan MPI on X122. Expect nodes 0, 2, 3.
3. From PCU, scan PROFIBUS on X101. Expect node 13.
4. Stop HMI Advanced on PCU. Open registry. Delete any NCULink_* or NCUAddressEthernet values.
5. Edit operator_panel.ini: BusType=MPI, BaudRate=1500000, NCK=0, PLC=2, MMC=3.
6. Set Personality=PowerLine in systemconfiguration.ini.
7. Restart HMI Advanced. Verify "Operator Panel" softkey is present, "NCU Link" is absent.
8. Confirm boot completes without alarm 120202.

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