SINAMICS S120 CU310-2 CF Corruption: Troubleshooting and Recovery

SINAMICS S120 CU310-2 CompactFlash Corruption: Field-Proven Troubleshooting and Recovery

1. Problem Overview

The SINAMICS S120 drive platform from Siemens relies on CompactFlash (CF) cards as the persistent storage medium for firmware images, parameter sets, topology descriptions, and license entitlements on its Control Units. When a CU310-2 DP, CU310-2 PN, or CU320-2 DP/PN control unit cannot complete a valid boot from its CF card, the drive produces a deterministic LED fault pattern that an experienced commissioning engineer can interpret without any diagnostic software attached. This article documents a real commissioning case involving a PM340 power module, a CU310-2 DP control unit, and a 1FT6082-8AK71 synchronous servo motor, where two consecutive CF cards were rendered unreadable because the host CF card slot on the control unit itself was mechanically damaged. The case demonstrates that a "corrupted card" symptom often masks a deeper mechanical fault in the host socket, and that recovery requires coordinated replacement of both the media and the control unit before firmware can be reloaded and the drive returned to service.

This technical reference consolidates the diagnostic logic, LED interpretation, Siemens catalog numbers, pin-level hardware requirements, firmware upgrade paths (V4.5 HF21 to V4.6), and STARTER commissioning workflow required to recover a CU310-2 from a CF-card-related fault state. The guidance is applicable to all CU310-2 firmware generations from V4.4 through V4.8, with version-specific notes called out where the procedure diverges.

2. Affected System Configuration

The reference line-up used to validate this recovery procedure comprises the following Siemens catalog numbers:

The CF card 6SL3054-0EF00-1BA0 is the standard Siemens-supplied media for the CU310-2 family and ships pre-imaged with the SINAMICS S120 firmware. The card uses a 50-pin CompactFlash Type I (CF-I) form factor and operates in TrueIDE mode once inserted into the CU310-2 socket. The CU310-2 itself does not contain internal flash for firmware storage; the CF card is the sole non-volatile boot medium. Removal of the card while 24 V control power is applied places the control unit into the boot-from-empty-card fault state.

3. Symptom Description and LED Fault Codes

On power-up, the CU310-2 executes a boot sequence that initializes the CF card interface, validates the firmware image header (magic number, signature, CRC32, version tag), and then loads the runtime firmware into internal RAM. If any stage of this sequence fails, the drive halts with a deterministic LED pattern on the front-panel indicators.

3.1 RDY and COM LED 2 Hz Flashing Pattern

The original commissioning attempt produced the following state on the CU310-2 DP front panel:

• RDY LED: Red, flashing at 2 Hz (0.25 s on, 0.25 s off duty cycle)
• COM LED: Red, flashing at 2 Hz
• OPT LED: Off or steady state depending on whether an option module (CBE20, Terminal Module, etc.) is mounted

Per the SINAMICS S120 List Manual (LH1), a 2 Hz red flash on RDY combined with a red flash on COM indicates one of three conditions:

1. The CF card is physically present but its firmware image is corrupted (bad CRC32, truncated image, signature mismatch, or version earlier than the bootloader minimum).
2. The CF card is present but contains no SINAMICS firmware (blank media, media formatted with a foreign file system, or media from a non-SINAMICS drive family).
3. The CF card slot cannot establish a stable electrical interface to the card because of damaged socket pins, contamination, or partial insertion.

The two-LED combination is intentionally redundant. RDY is driven by the bootloader's firmware-load state machine; COM is driven by the higher-level communications stack initialization. Both flashing red together unambiguously points to "no usable firmware image present" rather than a runtime application fault (which would normally show RDY steady green with a fault code on the diagnostic buffer).

3.2 Card Reader Cross-Check Procedure

Removing the suspected CF card from the CU310-2 and inserting it into a standard USB CF card reader on multiple PCs (Windows and Linux tested in the source case) failed to enumerate the card at all. This behavior is consistent with one of two root causes:

• The card's onboard IDE controller is electrically damaged and is not responding to the ATA IDENTIFY DEVICE (0xEC) command issued by the USB bridge.
• The card's flash memory has a corrupted card-information structure (CIS) that prevents the host from completing PC Card enumeration.

If a card fails to enumerate on a known-good USB reader, software-based recovery (quick format, image rewrite, chkdsk) is generally not possible. The card must be replaced. This cross-check is the single most valuable diagnostic step because it conclusively distinguishes "card is broken" from "socket is broken" when used in combination with the LED pattern.

4. Root Cause Analysis

The case described in the source material presents an instructive diagnostic chain worth documenting step by step, because the first conclusion was incorrect and the corrected conclusion required physical inspection of the control unit socket.

4.1 Initial Hypothesis: Card-Only Failure

The first 6SL3054-0EF00-1BA0 card failed enumeration in the CU310-2 slot, in two different USB readers, on four different PCs, and under two operating systems. This pattern strongly suggested that the card itself was defective, and a replacement was ordered from the supplier. Both cards (the original and the replacement) exhibited the same failure mode in the same CU310-2 socket. The replacement card arrived with a Siemens shipping inspection label, indicating it had been tested by Siemens prior to dispatch.

4.2 Corrected Hypothesis: Socket Pin Damage

Inspection of the CU310-2's CF card slot revealed two distinct mechanical faults:

1. Deformed pin: One contact pin in the socket was bent sideways, producing a corresponding indentation in the plastic shell of the CF card body when the card was inserted. This single bent pin is consistent with the failure pattern observed on both cards, because a bent pin will mechanically score the gold pads of the card and electrically short adjacent card contacts.
2. Extended pin: A second pin was pulled out of its housing and extended well above the plane of the other pins. This pin had been mechanically extracted from its retention spring, meaning it could not apply the specified 30 g normal contact force and was also misaligned laterally.

These two physical defects are sufficient to explain why two independent, individually-good CF cards both failed to function when inserted into this specific control unit. The diagnostic sequence "card fails, replace card, new card fails, inspect socket" is the correct workflow when the first replacement does not resolve the symptom.

4.3 CompactFlash Pin Count Requirements

The CompactFlash specification (CFA 4.1) defines a 50-pin connector, of which a subset is sufficient for basic 8-bit memory-card operation. The minimum signal set required for 8-bit TrueIDE mode is 19 active pins (data bus D0-D7, address lines A0-A10, chip selects /CE1 and /CE2, read strobe /IORD, write strobe /IOWR, interrupt /INTRQ, reset /RESET, card detect /CD1 and /CD2, power VCC, and ground). For this reason, mechanically damaged CF cards with one or two missing contacts can still function in many consumer applications such as digital cameras and PDAs.

The SINAMICS CU310-2 and CU320-2 control units, however, use the full 50-pin interface. The CF card slot on these control units engages all 50 contacts, and the drive's boot ROM validates the integrity of the interface as part of the startup sequence. Any bent, recessed, or extracted pin in the host socket can prevent the card from completing the ATA initialization handshake, even if the card itself is electrically healthy. The boot ROM's validation is strict on purpose: it prevents partial-communication states that could load a corrupted parameter set into RAM and produce unsafe motion.

5. Diagnostic Procedure

The following procedure should be executed in order before any CF card or control unit is replaced. Each step is designed to isolate the failure to one of three layers: card media, socket interface, or control unit electronics.

5.1 Pre-Power Safety Checks

1. Remove all power from the drive line-up, including the 24 V control supply to the CU310-2 (terminal X124).
2. Wait at least 5 minutes for the DC-link capacitors to discharge below 50 V. Verify with a CAT III 600 V meter on the DC-link test points (labeled DC+ and DC- on the PM340).
3. ESD-ground yourself via wrist strap before touching the CF card or control unit. The CF socket pins are exposed and ESD-sensitive.
4. Press the CF card eject button (located to the right of the slot on CU310-2) and remove the card.

5.2 Card Inspection and Validation

1. Examine the card edge connector under 10x magnification. Look for scoring, displaced gold pads, contamination, or melted plastic.
2. Insert the card into a known-good USB CF reader and verify it enumerates as a mass-storage device. A card that fails to enumerate in a healthy reader is electrically damaged and must be replaced.
3. If the card enumerates, mount it on the engineering PC and verify the presence of the firmware directory structure:
   • /ssr (firmware binaries by component)
   • /srt (runtime data)
   • /user (parameter sets, user projects)
   • license.txt (license metadata and CF card serial number)

Absence of these files means the card is blank, has been quick-formatted, or has a foreign file system. Reload the firmware via STARTER before further commissioning.

5.3 Socket Inspection

1. Examine the CF card slot on the CU310-2 under 10x magnification with a flashlight angled across the pin field. Side-illumination reveals bent or recessed pins that are invisible under direct lighting.
2. Verify that all 50 pins protrude to the same height (approximately 0.5 mm above the socket floor) and are aligned with the slot's central axis.
3. Verify that no pin is bent sideways, pushed below the surface, or extended above its neighbors.
4. Check for foreign objects (debris, solder balls, broken pin fragments) inside the slot. Use compressed air at low pressure (30 psi max) to clear the slot.

5.4 Control Unit Substitution Test

If the card and socket both appear intact but the drive still fails to boot with the 2 Hz RDY/COM flash, substitute a known-good CU310-2 of the same firmware generation into the line-up. Connect it to the same PM340 and motor, insert the same CF card, and apply 24 V control supply. If the known-good control unit boots successfully with the same card and PM340, the original control unit has an electronics fault beyond the CF socket and should be replaced.

6. Solution: Coordinated Card and Control Unit Replacement

The field-proven recovery path for the scenario documented in the source case is as follows:

6.1 Replace the Control Unit

Order a replacement CU310-2 DP with the same firmware generation as the original (V4.5 HF21 in this case). Note that the CF card from the original control unit is generally not transferable between control units of different firmware generations without a firmware reload step, because the CU310-2 validates the firmware version on boot and will reject an image older than its boot ROM expects.

6.2 Verify the New CF Card

The new control unit ships with a Siemens-branded 6SL3054-0EF00-1BA0 CF card pre-loaded with firmware V4.5 HF21. Verify the card is seated firmly in the socket and the ejector button is flush with the front panel. A partially seated card will produce the same 2 Hz RDY/COM flash as a corrupted card.

6.3 First Boot Sequence

1. Apply 24 V control supply to the CU310-2 at terminal X124.
2. Observe the LED sequence: RDY should flash green during boot (approximately 10-30 s for V4.5 HF21), then settle to steady green when the firmware is loaded.
3. COM should settle to steady green (if a DP master is connected and exchanging data) or off (if no master is present).
4. If both LEDs reach the expected steady states within 60 s, the drive is ready for commissioning. If RDY continues to flash red at 2 Hz after 60 s, the new card is defective (rare but possible) and should be exchanged through the dealer.

6.4 Confirm CF Card Enumeration on the Engineering PC

Insert the card from the new control unit into a USB reader and confirm the following files are present:

• /ssr/bin/CU3102_V4.5_HF21.bin - firmware binary
• /user/system.cfg - drive topology configuration
• license.txt - license metadata

If any of these are missing, the card was not properly imaged at the factory and should be exchanged through the dealer.

7. Firmware Upgrade: V4.5 HF21 to V4.6

Once the drive is operational with firmware V4.5 HF21, an upgrade to V4.6 may be performed if required by the application. The decision criteria are:

• Existing project with V4.5: Do not upgrade. The project configuration was validated against V4.5, and an upgrade can introduce parameter renumbering, default-value changes, or new safety checks that require a full re-commissioning cycle.
• Unconfigured (greenfield) system: Upgrade to V4.6. The latest firmware includes bug fixes, additional safety functions (Extended Functions via PROFIsafe), and updated motor data tables for newer 1FT6, 1FK7, and 1PH8 motor variants.

7.1 Required Components

Open STARTER and navigate to Help -> Installed Devices to confirm that SSP V4.6 is listed. If not, run the SSP installer (SINAMICS Setup Package V4.6) before proceeding. The SSP is a per-firmware add-on to STARTER that supplies the parameter descriptions and offline device masters required to configure a CU310-2 of that generation.

7.2 Firmware Upgrade Procedure

1. Connect the engineering PC to the CU310-2 service port (X127) via Ethernet. The service port is a dedicated 100 Mbit/s interface that does not interfere with the DP/PROFINET fieldbus.
2. Assign the service interface a static IP address in the 169.254.0.0/16 range, for example 169.254.11.22, with subnet mask 255.255.0.0 and no default gateway.
3. Open STARTER and create a new offline project for the CU310-2 DP at the CU's currently configured IP address (default 169.254.0.1, with PROFIBUS address 3).
4. Go online with the drive. STARTER will read the current parameter set and topology.
5. Open the Drive -> Updates / Firmware Update dialog.
6. Select the target firmware version (V4.6) and the target media (CF card).
7. STARTER will display a warning that the firmware on the CF card will be overwritten. Confirm.
8. The upgrade writes the new firmware to the CF card, verifies the CRC, and reboots the CU310-2. Total time is approximately 3-5 minutes. Do not interrupt 24 V control power during this window.
9. After reboot, go online again and verify that STARTER reports firmware V4.6 on the device under Drive -> Device Identification.

8. Commissioning the SINAMICS S120 Line-Up

With the firmware loaded and the CU310-2 booted clean, the 1FT6082-8AK71 synchronous motor can be commissioned. The 1FT6082 is an 80 mm frame, 8-pole, brushless permanent-magnet servo motor from the 1FT6 family. The -8AK71 suffix indicates the integrated encoder variant and shaft/key specification: typically a 24-bit absolute singleturn encoder (resolver-equivalent accuracy via EnDat interface) and a keyed shaft per DIN 6885.

8.1 Topology Configuration in STARTER

1. In the STARTER project tree, expand the SINAMICS_S120 drive object.
2. Right-click Configuration -> Automatic Configuration to have STARTER detect the PM340 power module and the connected motor encoder via the DRIVE-CLiQ interface or encoder port.
3. Verify that STARTER identifies the motor as 1FT6082-8AK71 with the correct encoder type (EnDat 2.1 or 2.2 depending on motor date code).
4. Accept the configuration and download to the drive. STARTER will prompt for a Copy RAM to ROM, which writes the topology to the CF card.

8.2 Motor Identification

1. Open Drive -> Commissioning -> Motor Identification.
2. Set p1910 = 1 for the standstill measurement (stator resistance, leakage inductance).
3. For rotating measurement of the flux characteristic and moment of inertia, set p1960 = 1 and ensure the motor is decoupled from the load before starting.
4. Execute the identification run by issuing an ON command. The drive will perform the measurement and report completion via r0047.
5. Save the identified parameters to the CF card via Drive -> Copy RAM to ROM (equivalent to setting p0977 = 1).

8.3 Encoder Calibration

1. If the motor uses an absolute encoder (the -8AK71 variant), perform a one-time absolute encoder calibration on first commissioning.
2. Mechanically move the motor to a known reference position, or use the existing absolute position if the motor has not been moved since power-off.
3. Set p2596 = 1 to apply the absolute encoder offset, then save to ROM.

8.4 Key STARTER Parameters

9. Verification

After the firmware upgrade and commissioning steps are complete, perform the following verification sequence to confirm the drive is operating correctly:

10. Preventive Measures

To reduce the likelihood of CF card corruption in operating SINAMICS S120 line-ups:

1. Handle CF cards by the edges only. Skin oils and ESD events degrade the gold contact pads over time. Use the eject button rather than prying the card out with a tool.
2. Insert the card with the correct orientation. Reverse insertion bends the host socket pins and damages the card in one motion. The CF card top label (Siemens logo and firmware version) should face the drive's outer panel when the eject button is on the right.
3. Verify socket condition annually. In dusty environments, use compressed air to clear the CF slot during scheduled maintenance. In high-vibration environments (presses, stamping machines), inspect the socket pins for fretting corrosion during the same maintenance window.
4. Maintain a known-good spare. Stock one verified 6SL3054-0EF00-1BA0 card per critical drive, imaged with the same firmware version as the production drive. Spare cards older than 24 months should be re-verified by inserting them into a USB reader quarterly.
5. Always save parameters to ROM after commissioning. This writes the active parameter set to the CF card so that a control unit swap does not require a full re-commissioning. The Copy RAM to ROM command in STARTER is the single most important step before a hot-cutover.
6. Avoid quick-formatting operational CF cards. The SINAMICS firmware images the card with a non-standard file system layout that a quick-format will destroy. If a quick-format is performed as a recovery step (for cards that fail to enumerate as mass-storage but are otherwise intact), the firmware must be reloaded immediately via STARTER.
7. Avoid UPS-induced voltage transients on the 24 V control supply. Brown-outs below 19 V during CF card write operations can corrupt the file system. Specify a 24 V supply with ride-through of at least 20 ms at full load.

11. Related Fault Patterns and Cross-References

The CU310-2 family can also produce the 2 Hz RDY/COM flash pattern for the following related causes, each of which should be ruled out before replacing either the card or the control unit:

The CU310-2 also reports firmware-related faults in its diagnostic buffer as F01000-F01099 range codes. F01018 typically indicates a CF card read error, while F01019 indicates a firmware version mismatch. The detailed fault cause and remedy are available in the SINAMICS S120/S150 List Manual parameter descriptions for these fault codes.

12. Frequently Asked Questions