Resolving Sinamics S120 F01650(1000): SI Checksum Mismatch Fix

1. Problem Statement: F01650(1000) on a Sinamics S120 Drive

After a safety-related parameter change is performed offline (for example, editing p9659, p9620, p9650, or any other Safety Integrated parameter) and downloaded to the drive, the Sinamics S120 raises fault F01650 with fault value 1000 the next time the unit is switched on. The drive refuses to enable and any motion command returns the fault immediately, even when the parameter value itself looks correct.

Fault value 1000 means that the reference checksum stored in the drive and the actual checksum computed at boot do not match on monitoring channel 1 (MCU 1). Because the parameter set has been altered while the drive was offline, the Safety Integrated firmware in channel 1 detects the discrepancy and latches the fault until a valid acceptance test has been performed and the reference checksum is updated.

Related fault values that are commonly seen in the same workflow include 2005 (functional safety checksum has changed, acceptance test required) and 2xxx family messages from the safety logbook. The same recovery workflow applies to all of them: re-run the safety commissioning online, accept the new reference checksum, then execute a documented acceptance test.

2. Affected Products and Firmware

Component	Order number	Relevant firmware	Notes
Control Unit CU320-2 DP	6SL3040-1MA00-0AA0 / -0AA1	≥ V4.4 (SI Basic Functions)	Used in S120 Booksize and Chassis
Control Unit CU320-2 PN	6SL3040-1MA01-0AA0 / -0AA1	≥ V4.4 / V5.x	PROFINET variant
CU310-2 DP / PN	6SL3040-0LA00-0AA0 / -0LA01-0AA0	≥ V4.4	Single-axis Control Unit
TM54F	6SL3055-0AA00-3FB0	Matches host CU	Terminal Module for F-DI/F-DO
Memory card (CompactFlash)	6SL3054-0EF00-1BA0 (8 MB) / 6SL3054-0AA00-1BA0 (16 MB)	N/A	Defective card is a known root cause of persistent F01650

F01650 is only raised on drive objects that have Safety Integrated Basic or Extended Functions enabled. The fault appears with code 01650 hex (decimal 5712) and is shown in STARTER / Startdrive under the faults tab of the affected drive object. The reference documentation is the SINAMICS S120/S150 List Manual and the SINAMICS S120 Safety Integrated Function Manual.

3. Decoding F01650 — Fault Value Reference

The drive evaluates F01650 with a numeric fault value (the number shown in parentheses). The most common values are listed below; the value directs the remedy path.

Fault value	Meaning (per list manual)	Typical cause
0	No additional information	Generic checksum discrepancy
1000	Reference and actual checksum on monitoring channel 1 are not identical (booting)	Safety parameter set changed offline; current controller sampling time p0115[0] modified so r9780 changed; checksum-checked data block defective; safety parameters set offline and loaded into the CU
2000	Safety logbook checksum error / channel 2 mismatch	Internal logbook integrity loss
2005	Functional safety checksum has changed; acceptance test is required	Parameter change that mandates a new acceptance test report
6000 / 6063 / 6064	Channel-2 reference checksum / actual checksum / SI parameterization error	DRIVE-CLiQ wiring, MCU2 firmware mismatch, wrong TM54F parameter set

Always read both the fault code and the fault value when working on this class of fault — they are independent and the value selects the remedy.

4. Root Cause: How Offline Parameter Changes Break the Safety Checksum

Every Safety Integrated parameter group has an associated reference checksum. The drive stores two checksums per monitoring channel:

• r9798 — actual checksum, channel 1. Recalculated at each boot from the current SI parameter set.
• p9799 — reference checksum, channel 1. The value committed to non-volatile memory after a successful safety commissioning and acceptance test.

For monitoring channel 2 the equivalent tags are r9898 and p9899. Checksum values are unsigned 32-bit integers, displayed in the expert list as decimal or hex depending on the firmware version.

When the safety parameters are edited in the STARTER / Startdrive project navigator while the drive is offline, the SINAMICS tooling updates the project checksum but does not update the reference checksum on the target. After the project is compiled and downloaded, the boot-time actual checksum r9798 (computed from the new SI parameters) no longer matches p9799 (the old reference) and the drive raises F01650(1000). This is the most common path to the fault.

Equally, if p0115[0] (current controller sampling time) is changed, the Safety Integrated monitoring cycle r9780 is automatically adapted, which in turn changes the calculated checksum. F01650(1000) can therefore be raised by a non-safety parameter change that nevertheless alters the SI cycle.

5. The Three Legitimate Remedies Listed by the Firmware Manual

The SINAMICS S120 list manual gives the following remedies for F01650(1000):

1. Check the SI Basic Functions monitoring cycle r9780 and adapt the reference checksum p9799 to match.
2. Perform the safety commissioning routine online.
3. Replace the memory card or the Control Unit if the checksum-checked data block is corrupted.
4. Activate the safety parameters for the affected drive through STARTER / Startdrive (modify settings → copy parameters → activate settings).

Items 1, 2, and 4 are always done on the live drive, never offline. Item 3 only applies when the non-volatile media is suspect. A fourth, often-overlooked remedy is to issue an explicit Copy RAM to ROM after the safety activation, otherwise the new reference checksum is held in volatile memory and the next cold start reverts the drive to the old p9799.

6. Prerequisites Before Touching Safety Parameters

• You must have STARTER (≥ V5.1 SP1) or Startdrive (≥ V15.1) installed, with the matching SINAMICS SSP support package for the firmware installed on the CU.
• The commissioning engineer must have the Safety Integrated password set in p9761 / p9762 (default "0" on a fresh unit) and the password must be known to the operator.
• You need the original machine project (with the project checksum) and a verified backup of the CU on a working memory card.
• STARTER / Startdrive must be online with the drive and able to read the actual parameter r9798 from the live system.
• Stop all motion. The drive must be in the Commissioning or Ready state; the Safety Integrated commissioning mode must be enabled for the duration of the change.

7. Resolution Workflow — The Online Safety Integrated Dialog

The only correct way to modify a safety parameter is through the Safety Integrated dialog of the drive object, online. The dialog enforces the checksum recalculation and the activation sequence that the firmware expects.

1. Connect STARTER or Startdrive to the CU over PROFIBUS, PROFINET, or Ethernet service interface, and go online with the affected drive object.
2. Open the drive navigator. The Safety Integrated configuration is reached from the right-hand panel "Safety Integrated" or by double-clicking the safety icon under the drive object.
3. Open the Safety Integrated commissioning dialog. Click "Change settings" — STARTER will prompt for the safety password (p9761 / p9762). Enter it.
4. Edit the parameter that triggered the checksum mismatch (for example p9659, p9620, p9650). Make the required change.
5. Click "Copy parameters". The tooling writes the new parameter set to the RAM of channel 1 and channel 2.
6. Click "Activate settings". The drive runs the safety parameterization, computes the new r9798 and r9898, writes the new p9799 and p9899 to non-volatile memory, and updates the project checksum.
7. Confirm the prompt. STARTER will indicate that the unit needs a power cycle. Power the CU off and on (or issue a software reset from STARTER).
8. After the boot, read r9798 and r9898 from the expert list. They must be equal to p9799 and p9899 respectively. F01650 must be cleared.

If F01650 returns after the next cold boot, the activation did not reach the non-volatile memory. Repeat steps 5–6 and then issue an explicit Copy RAM to ROM from the drive object toolbar before powering down.

8. Safety IBN (Commissioning) Mode for the First-Time Procedure

On a brand-new CU, or after a complete project download, the safety commissioning mode has to be selected so that the dialog exposes the configuration buttons. From the Safety Integrated dialog:

1. Select the option "Enable safety commissioning mode". The dialog will request the safety password.
2. Make the parameter change.
3. Click "Copy parameters", then "Activate settings".
4. Exit commissioning mode. The drive will request a power ON to commit the new reference checksum.

Commissioning mode is required because p9761 (safety password) is locked out during normal operation. Without commissioning mode the "Activate settings" button is greyed out and p9799 cannot be updated.

9. Adapting p9799 Directly (Only When the Drive Specifically Indicates So)

If the list manual diagnostic step explicitly says "adapt the reference checksum p9799 to the actual value", do not type a guessed number. The correct procedure is:

1. Go online and read r9798 from the expert list.
2. Set p9799 = r9798. Sign the change with a Copy RAM to ROM.
3. Perform the safety acceptance test (see section 11).
4. Power off / on.

This is only valid when the change is justified by an update to r9780 (monitoring cycle) caused by p0115[0]. In every other case the online Safety Integrated dialog is the only acceptable path — direct parameter writes to p9799 are not logged in the safety logbook and break the audit trail.

10. Memory Card Failure as a Persistent Root Cause

A non-volatile media failure is the most common cause of F01650(1000) that survives a correct online safety commissioning. Symptoms:

• The fault returns immediately after every Copy RAM to ROM.
• The CU LED pattern shows the safety fault even on a freshly blanked card after a project download.
• STARTER reports a "checksum error" on the safety logbook tab.
• Replacing the card with a verified card and reloading the project clears the fault permanently.

Approved replacement cards for the CU320-2 family include the 8 MB CompactFlash card 6SL3054-0EF00-1BA0 and the 16 MB variant 6SL3054-0AA00-1BA0. Use only Siemens-supplied cards; third-party CF cards frequently fail the wear-levelling checks built into the CU firmware and re-introduce the same fault within weeks.

After fitting a new card, the project must be reloaded with STARTER / Startdrive, the safety commissioning must be re-run online, and a full acceptance test performed. The memory card is then the non-volatile media for the new reference checksums p9799 / p9899.

11. Verification — Acceptance Test and Signal Forcing

To prove the fault is fixed and the safety chain is functional, force the Safe Torque Off input (typically p9620[0] on the CU) through the documented sequence:

1. With the drive in Ready and the enable set, read the safety status words r9722 / r9872. They must show STO inactive.
2. De-energise the F-DI wired to p9620[0] (logic 1 → 0). The drive must go to STO active and remove the enable from the motor within r9780.
3. Re-energise the F-DI (logic 0 → 1). The drive must return to Ready and accept the next enable command without raising F01650.
4. Record the test results in the acceptance report. Include the actual r9798 / r9898 and the updated p9799 / p9899 values, the date, and the signature of the responsible engineer.

If the test fails on step 2 or 3, the F-DI wiring or the p9620 source selection is wrong — fix the wiring and re-test before re-trying the safety commissioning. The STO function is not a software-only feature; the physical wiring, terminal jumpers, and the CU input debounce time (p9650) all participate.

12. Field Troubleshooting Matrix

Symptom	Most likely cause	First action	Confirm by
F01650(1000) after offline edit of any p96xx / p97xx parameter	p9799 not updated	Re-run the Safety Integrated dialog online with "Activate settings"	r9798 == p9799 after boot
F01650(1000) appears only when p0115[0] is changed	r9780 changed, p9799 stale	Set p9799 = r9798, perform acceptance test	No fault after power on
F01650(1000) returns after every Copy RAM to ROM	Memory card defective	Replace with approved CF card, reload project, re-run safety commissioning	Fault cleared permanently across cold starts
F01650(2005) and (1000) both present	Logbook + boot checksum both stale	Online safety commissioning, then acceptance test, then re-evaluate the card	Both values cleared
F01650(6063) or (6064)	Channel 2 SI parameterization error / TM54F mismatch	Verify DRIVE-CLiQ topology, MCU2 firmware matches MCU1, re-run safety commissioning	r9898 == p9899
F01650 only on one drive object of a multi-axis DCC	Drive object has its own SI configuration	Open the Safety Integrated dialog of that specific drive object, not the CU	Fault cleared on that DO only
F01650 returns only after a mains-off / mains-on cycle	Copy RAM to ROM was missed	Repeat the activation, then issue explicit Copy RAM to ROM	Survives a cold start

13. Preventive Practice on the Shop Floor

• Always make safety parameter changes from the online Safety Integrated dialog, never from the expert list while offline.
• Never edit p96xx / p97xx parameters via the project navigator when the drive is in production. Treat the project file as read-only once the safety acceptance report has been signed.
• Document p9799 and p9899 in the acceptance report. If the value is ever lost, the report is the only way to restore the correct reference.
• Issue Copy RAM to ROM after every successful safety activation. A power loss before the copy rolls back to the previous reference checksum and raises F01650 at the next boot.
• Keep a known-good backup memory card in the panel. Field engineers can swap and reload within minutes instead of fighting a corrupted card for hours.
• Use the same STARTER / Startdrive version (same SSP) on the production line as on the engineering bench — checksum changes between SSP versions are a documented source of false F01650 events after a routine firmware refresh.

14. Related Faults to Keep in Mind

F01650(1000) frequently travels with adjacent safety messages that have to be cleared in the same acceptance window:

• F01650(2005) — functional safety checksum has changed; acceptance test required.
• A01650 / C01650 — non-fatal variants of the same discrepancy, often used to warn of pending changes before the next power-on.
• F01651 / F01652 — SI monitoring channel 2 / cross-check error. Indicates MCU1 and MCU2 parameter sets disagree; the drive has to be re-commissioned with both channels.
• F30802 — SI: defective RAM / ROM block on channel 2. Forces a card or CU replacement.

Always read the full fault buffer (r0945 / r0947 / r0949) before closing the issue, and ensure the safety logbook entry written by the firmware matches the version stamped on the acceptance report.

15. When to Escalate Beyond Drive Commissioning

If F01650(1000) returns after the online safety commissioning, after a card replacement, and after a verified spare CU has been substituted, the root cause is upstream of the drive:

• 24 V supply noise on the F-DI line — the STO input is bouncing, the SI logic interprets the cycle slip as a checksum invalidation.
• DRIVE-CLiQ wiring between the CU and the TM54F or the Motor Module with intermittent contacts — re-seat the connectors and re-measure the DRIVE-CLiQ diagnostics counters (r9946).
• Project mismatch between the SSP installed in STARTER / Startdrive and the firmware on the CU. The tooling writes a parameter format the firmware then rejects as a checksum mismatch.
• Grounding issue on the motor feedback — SSI / EnDat / resolver feedback corruption can be re-routed through the SI logic when the safety configuration uses the encoder.

For all of these, the remediation is to fix the upstream condition, repeat the online safety commissioning, and re-issue the acceptance report. The drive itself is not defective.

FAQ