SINUMERIK 802D Startup Menu: Resolving Missing Load Options

When a SINUMERIK 802D numerical control is brought back online after a multi-day mains power outage, the HMI can present a reduced startup menu showing only NORMAL MODE, SOFTWARE UPDATE, and PLC STOP. The Load Standard Data and Load Saved Data entries that are normally available in commissioning state are missing, and any attempt to confirm a default-data load returns the operator to the same dialog. This article documents the root cause, the verification checks, and the recovery procedure that bring the full startup tree back without losing machine data, drawing on the field case of a SINUMERIK 802D sl that had been de-energized for four days before being restarted.

1. SINUMERIK 802D Startup Architecture

The SINUMERIK 802D sl is built around three functional blocks: the NCK (NC kernel) for path and axis control, the integrated PLC (S7-200 compatible instruction set) for machine I/O, and the PCU 50.3 (Personal Computer Unit) that runs the HMI software on a Windows CE / Windows XPe embedded image. The product family is documented on the SINUMERIK 802D sl product page in the Siemens Industry Online Support portal.

On power-up the PCU executes a controlled boot sequence, then hands off to the HMI. If the integrated PLC is stopped, the HMI startup tree shows a different set of options. If the NCK or HMI detects a configuration drift (for example, a saved-data set that no longer matches the current machine data), additional menu items are surfaced for the user to either keep working data or reload from a known-good image.

The full commissioning state startup tree on a SINUMERIK 802D sl lists, in order:

1. Normal mode (start NC + PLC with current data)
2. Software update (firmware / HMI image)
3. PLC stop (start HMI and NC, leave PLC in STOP)
4. Start with default data (load standard machine data)
5. Reload saved user data (load backed-up NC / PLC / HMI data)
6. Setup mode / End setup (commissioning entry / exit)

The reduced three-option menu corresponds to the operator (User) access level where commissioning entries are hidden. The PCU 50.3 boot sequence timing is approximately:

2. Protection Key Levels and Access Control

Access to the startup menu options on the 802D is gated by the active protection key level. The levels are evaluated in this order, and the active level is held in NCK machine data (typically in the MD51074 to MD51125 range for access control flags) backed by the SRAM battery:

If the password input on the HMI shows a non-zero protection level, the NCK hides the "Start with default data" and "Reload saved user data" menu items to prevent operators from clobbering commissioned data. The reduced menu is therefore not a fault; it is the expected view at User level. The key question is why the system is sitting at User level after a power loss when commissioning entries were visible before the outage.

3. Root Cause Analysis

Three root-cause families have to be considered for this symptom. Each one has to be ruled in or out by physical measurement before any HMI action is taken.

3.1 Power supply and grounding integrity

Four days of mains outage will discharge the buffer capacitor that holds the access level across a short power dip, but it should not corrupt the SRAM that stores the password and machine data if the lithium backup battery is healthy. Where the battery is marginal, the NCK boots with the protection level reset to User (0) and the operator password is blank. In that state, the menu collapses to the three-item view. The 24 V DC rail at the PCU connector must therefore be measured, and the PE bond on the PCU chassis must be verified, before any password or data operation is attempted.

3.2 Battery-backed SRAM state

The SRAM that holds the protection level, compensation data, and the PLC retentive flags is backed by a 3 V lithium cell (typically CR2032 or equivalent, Siemens part number 6FC5247-0AA18-0AA0 on the 802D sl PCU 50.3). If the cell voltage drops below 2.5 V while mains is removed, the cell cannot hold the data and the NCK boots in the as-shipped state. A 4-day outage is well within a healthy cell's hold-up time, but a cell that is several years old or that has been through a previous deep discharge will fail this test. Measure the cell voltage with the PCU powered down for at least 60 s so the cell is not under load.

3.3 PLC STOP versus NC STOP

Selecting PLC STOP in the HMI startup menu does not stop the NCK; it leaves the NCK running with the last valid machine data and just prevents the integrated PLC from cycling. If the HMI presents the three-item menu and PLC STOP is one of them, the integrated PLC is already in STOP and the HMI is essentially saying "I cannot start the full machine because the PLC will not run." This is the second-most-common cause of the three-item menu after the access level reset, and the two causes can coexist.

4. Hardware Verification: 24 V DC Supply, PE, and Connector Reference

Before any HMI navigation, confirm the PCU supply and chassis ground. The PCU 50.3 used in the 802D sl is specified for a 24 V DC nominal input with the following limits:

Pinout of the PCU 50.3 supply connector X1 (top entry, screw terminal):

Procedure at the PCU terminal block:

1. Isolate mains at the cabinet disconnect and verify zero energy on the 24 V DC bus with a DMM.
2. Inspect the PE bonding strap from the PCU chassis to the cabinet ground bar. Loose paint, anodized paneling, or a missing star washer will defeat the bond. Re-terminate to ≤ 0.1 Ω.
3. Re-energize the 24 V DC bus and measure at the PCU X1 connector with the PCU load attached. Accept 20.4 V to 28.8 V DC under load. If the voltage droops more than 0.5 V between no-load and PCU-loaded, the power supply unit is undersized or the cable run is too long for the gauge.
4. Check the 0 V (M24) terminal of the PCU is bonded to the same ground bar as the PE. A floating 0 V is a frequent cause of corrupted files on the HMI flash after a power event.
5. Measure the backup cell voltage at the test points on the PCU 50.3 motherboard. A reading above 2.9 V indicates a healthy cell; 2.5 V to 2.9 V indicates end-of-life and imminent replacement; below 2.5 V indicates the cell has already lost data and must be replaced before the next commissioning.

5. Step-by-Step Recovery Procedure

Use this sequence to bring the full startup tree back. Do not skip the power verification step; the 802D NCK will refuse to commit a default-data load if the 24 V DC rail is marginal, and the operator will see the same menu repeat on each reset.

1. Confirm the 24 V DC rail at the PCU and the PE bond per Section 4.
2. Power-cycle the PCU and observe the LEDs on the front bezel. A normal boot shows: PWR (steady green), HDD activity (brief amber flash), and the HMI progress bar advancing to 100 % within 60-90 s.
3. When the three-item menu appears, do not select any option. Press the horizontal softkey F2 once, then the vertical softkey F2 once. This is the documented key sequence to reveal the commissioning state, which adds the "Start with default data" and "Reload saved user data" entries to the menu.
4. If the additional entries appear, the NCK was simply guarding them behind a service-level key. Select "Reload saved user data" to restore the last backup, or "Start with default data" only if a backup does not exist and the machine has to be recommissioned.
5. If the F2-F2 sequence does not reveal the additional entries, the protection level may be set explicitly to User (0) by a machine data setting. Connect a Siemens PG/PC with the SINUMERIK commissioning tool over Ethernet and inspect the active protection level via the HMI diagnostics page (see Section 10).
6. Wait for the NCK to finish writing to flash. Do not power-cycle during the write. A power loss here corrupts the data image and forces a full reload from a backup.
7. On the next cold start, the full menu should be present. If the menu collapses again, the battery cell is failing and must be replaced.

5.1 State diagram of the recovery flow

6. Restoring Standard and Saved Data

The "Start with default data" entry on the 802D sl loads the as-shipped machine data set. This wipes compensation tables, leadscrew error compensation, software limit switches, and any saved PLC retentive flags. It is the correct choice when the saved-data set is known to be corrupt or when the machine is being recommissioned. It is the wrong choice on a production machine that has a valid backup.

The "Reload saved user data" entry restores the most recent backup, which is stored on the HMI flash as a series commissioning archive. The procedure is:

1. Enter the commissioning state by revealing the menu per Section 5.
2. Select "Reload saved user data".
3. Confirm with the manufacturer-level password when prompted. The default manufacturer password on a SINUMERIK 802D sl out-of-box is SUNRISE; OEMs change this on commissioning. A lost password cannot be reset from the HMI and requires a Siemens service call with proof of ownership.
4. Wait for the HMI to display "Data load complete" before continuing.
5. Reset the NCK with "NCK RESET" on the HMI diagnostics page or via the PLC interface.

If the saved data set is missing or unreadable, the HMI returns to the three-item menu on the next reset. In that case, fall back to "Start with default data" and re-commission the machine, then save a fresh series commissioning archive as the new baseline.

7. PLC STOP versus NORMAL MODE Behavior

PLC STOP on the 802D sl holds the integrated PLC in STOP without affecting the NCK. The HMI is fully functional, but no PLC user program is being executed, so all machine I/O is frozen. This mode is intended for safe data operations on the NCK while the machine is mechanically disabled. It is not a fault state.

If the operator previously selected PLC STOP and the saved configuration contains an explicit "start with PLC stop" flag (machine data MD20150 $MC_GCODE_RESET_VALUES or the equivalent access flag in the startup area), the HMI may present the three-item menu on every subsequent boot until the flag is cleared in the commissioning state. The flag is cleared by:

1. Enter the commissioning state and load saved user data.
2. On the HMI, navigate to Setup > Machine Data > NCK > Startup and clear the "Start with PLC stop" bit.
3. Save the machine data, then cycle NCK.

8. Alarm Codes and Diagnostics

The alarms most often raised in this scenario are listed below. All alarm codes are documented in the SINUMERIK 802D sl Diagnostics Manual and the Lists Manual in the Siemens Industry Online Support portal.

Active alarms can be read on the HMI under Diagnosis > Alarm Log or via the PLC status word when the HMI is online. Each alarm has a clear number and a clear-condition description in the manual. The 802D sl retains the last 100 alarms in the persistent log, which survives a power cycle if the backup cell is healthy.

9. Commissioning Tool Access via Ethernet

Where the F2-F2 softkey sequence does not reveal the commissioning state, the active protection level can be read and changed from a Siemens PG/PC running the SINUMERIK commissioning tool. The procedure is:

1. Connect the PG/PC to the 802D sl PCU 50.3 on the X127 Ethernet port (10/100 Mbit, RJ45) with a crossover or direct cable depending on the PG/PC NIC.
2. Set the PG/PC NIC to the 802D default subnet: IP 192.168.214.1, mask 255.255.255.0. The 802D sl PCU defaults to 192.168.214.1; verify on the HMI under Setup > Network.
3. Start the commissioning tool and connect to the 802D NCK. The tool will prompt for the current access password if the active level is not User.
4. Read the active protection level under Diagnostics > NCK > Protection level. Confirm the value matches the expected commissioning level (typically 1 or 2).
5. If the level has been reset to 0 by a battery failure, change the access password to restore the desired level. The new value is written to SRAM and held by the backup cell.

10. Prevention: Hardening for the Next Power Event

To prevent recurrence on the next outage or brownout, apply the following on every 802D sl in service:

1. Replace the PCU 50.3 backup cell on a 5-year cycle or after any deep discharge event. Use only the Siemens-approved cell (part 6FC5247-0AA18-0AA0); generic CR2032 cells have lower capacity and shorter service life in the 802D holder.
2. Install a 24 V DC UPS (buffered 24 V supply) on the PCU feed. A 30 s hold-up is sufficient to ride through most utility recloses; a 5-minute hold-up covers a controlled shutdown.
3. Bond the PCU chassis to the cabinet ground bar with a dedicated PE strap, not via the DIN-rail clip. The DIN-rail clip is a mechanical retention point, not a code-compliant PE bond.
4. Bond the 0 V terminal of the PCU to the same ground bar as the PE. A floating 0 V will inject common-mode noise on the HMI flash and corrupt the data image during a power event.
5. Create a series commissioning archive after every parameter change. Store the archive on an external backup so it survives a PCU flash failure. The archive is created on the HMI under Setup > Series Commissioning > Create Archive.
6. Document the current manufacturer password in a secure location. A lost password on a 802D sl requires a Siemens service call to reset; it cannot be bypassed from the HMI.
7. Add a 24 V DC power monitor with a dry-contact alarm output to the cabinet. Wire the contact to a PLC input that generates an HMI alarm when the 24 V DC rail drifts out of the 20.4 V to 28.8 V window. The early warning gives the operator time to perform a controlled shutdown before the next brownout corrupts the data image.

11. Verification

Confirm the recovery is complete by running the following checks:

1. Power-cycle the PCU twice. The full startup menu (six entries) must appear on each cold start.
2. Read the alarm log under Diagnosis > Alarm Log. Only the alarms raised by the data load (1040, 15100) should be present. Battery-related alarms or 16906 must not reappear on the next power cycle.
3. Measure the 24 V DC rail at the PCU X1 connector with the PCU running. It must remain within 20.4 V to 28.8 V DC under load.
4. Measure the PE resistance from the PCU chassis to the cabinet ground bar. It must be ≤ 0.1 Ω.
5. Measure the backup cell voltage with the PCU powered down for 60 s. It must be above 2.9 V for a 5-year service life; replace if below 2.7 V.
6. Run a controlled test power event: open the 24 V DC breaker for 30 s, restore, and confirm the full menu is present on the next cold start and the saved user data loads cleanly.
7. Confirm the protection level read from the commissioning tool matches the expected commissioning level. A level-0 reading after a successful recovery indicates the backup cell is failing and must be replaced before the next commissioning event.

If any verification step fails, return to Section 4 and re-check the 24 V DC and PE chain before assuming a software fault. The 802D NCK is conservative: it will refuse a default-data load and present the three-item menu again rather than risk corrupting the data image on a marginal supply.

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