Resolving SINAMICS A07565 Encoder Error on SMC30 with Zero Mark

Problem Overview

The fault A07565 (F, N) Drive: Encoder error in PROFIdrive encoder interface 1 is raised on a SINAMICS drive (controlled by a SINUMERIK 840D sl / 828D or SIMOTION / SIMATIC axis) when the user enables a zero-mark-based reset of an external incremental encoder via parameter p4652 = 1 while the encoder signal is processed through a SMC30 Sensor Module. The alarm appears the first time the zero mark is evaluated, even though the encoder appears mechanically and electrically healthy.

The reported environment is a customer machine that uses an Emerson Universal SM-Encoder Plus as a simulated incremental encoder source. The SMC30 reads track A/B and the zero pulse, and the application expects a deterministic position reset to zero on every detected zero mark.

A second, recurring manifestation appears after maintenance actions: when the encoder cable (for example a resolver cable that was temporarily removed) is reconnected and insulation-tested with a megger at 500 V DC, the next zero-mark event generates the same A07565 even though the cable passes the insulation test.

Affected Components, Firmware, and Topology

The PROFIdrive encoder interface that the alarm refers to is the standardized G1_ZSW / G1_XIST1 / G1_XIST2 process data exchanged between the SINAMICS drive and the higher-level controller.

Root Cause Analysis of A07565

Alarm A07565 is raised by the SINAMICS firmware when the drive detects that the controller has signaled an encoder error in the PROFIdrive encoder interface of encoder 1:

• Bit G1_ZSW.15 (encoder error / fault) is set to 1 by the controller.
• The actual error code is transported in G1_XIST2 and mirrored into r0483[0].
• Alarm value r2124 (interpret as decimal) contains the same code and must be decoded against the r0483 description.

Two preconditions must be true for the alarm to be issued at all:

1. The PROFIdrive encoder interface must be enabled for encoder 1.
2. The controller must write to G1_XIST2 a non-zero error code at the moment the zero mark is processed.

Key constraint (firmware invariant): This alarm is only output if p0480[0] ≠ 0. If p0480[0] = 0, the PROFIdrive encoder interface is disabled and A07565 cannot be raised regardless of the controller state. This is the single most important parameter for this fault.

PROFIdrive Encoder Interface Signal Flow

The error originates on the controller side, not in the SMC30 itself. The simplified sequence is:

Parameter Reference

SMC30 Wiring and Configuration Pre-Checks

Before changing p4652 or the controller program, validate the physical layer. Roughly 40 % of A07565 events seen in the field are caused by a zero-mark signal that is either not connected, inverted, or has insufficient pulse width.

1. Verify the SMC30 wiring at terminal X521:
   • Pin 1 = track A+
   • Pin 2 = track A−
   • Pin 3 = track B+
   • Pin 4 = track B−
   • Pin 5 = zero mark R+
   • Pin 6 = zero mark R−
   • Pin 7/8 = encoder supply (typically 5 V or 24 V per p0405)
2. Confirm p0405 = 1 (5 V) or p0405 = 0 (24 V) matches the Emerson output. A mismatch produces a degraded zero-mark and intermittent A07565.
3. Set p0425 = 1 to declare that the zero mark is wired.
4. Set p0430 to match the signal standard (TTL or HTL bipolar).
5. With the drive in commissioning mode, monitor r0061[0] (actual speed) and r0480 / r0481[0] (raw position counter). A smoothly changing counter with consistent increments confirms good A/B; a clean step at one position per revolution confirms the zero mark.

Step-by-Step Resolution

Use the procedure below on the offline / online project of the drive. All writes are online via Starter, Startdrive, or SCOUT. On SINUMERIK HMI, the same parameters are visible under Commissioning > Drive parameters > Expert list.

Step 1 — Capture the actual alarm value

1. Connect to the drive online.
2. Open the expert list.
3. Read r2124 (decimal) and r0483[0] (hex). Note the exact value before any reset action.
4. If the alarm value is 0, the alarm has already been cleared and the next zero mark event will regenerate it. Re-trigger by rotating the encoder one revolution past the zero mark.

Step 2 — Eliminate the controller-side cause

The controller writes the error code that triggers A07565. Common controller-side causes:

• The PLC / NC program contains a logic block that evaluates EncoderError from the encoder telegram and copies it into G1_XIST2.
• A referencing block forces G1_ZSW.15 = 1 if the zero mark is detected before the axis is referenced.
• The reference-point-approach state machine in the NCK sets the error bit transiently during search-for-zero (typical during first referencing after power-up).

Step 3 — Re-enable the reset only after referencing is complete

If the application truly needs p4652 = 1, gate it from the controller so that the reset is only permitted when DB31, … DBX60.4 (referenced / synchronized) is set on the SINUMERIK side, or the equivalent "axis referenced" flag on SIMOTION / SIMATIC. This prevents the controller from raising the encoder error during the first pass of the zero mark.

; STL / SCL snippet, SIMATIC S7-1500T or SINUMERIK PLC
IF "Axis".StatusBits.Refenced AND "Axis".Position < 0.001 THEN
    Drive_Control.P4652 := 1;   // reset with next zero mark
ELSE
    Drive_Control.P4652 := 0;
END_IF;

Step 4 — Verify parameter persistence

1. Save the project to the CFast / SD card.
2. Power-cycle the drive and confirm p0480[0] and p4652 retain their intended values.
3. Read back r3996[0] for the effective parameter set after boot.

Diagnostic Procedure

Use this matrix when the alarm returns after a fix attempt.

Cable and Insulation-Test Considerations

The second scenario — where the alarm appears after a megger test at 500 V DC — is not a fault of the SMC30 but a remnant of the test procedure. Insulation testing injects high DC into the conductor-shield capacitance; if the SMC30 or the encoder simulator is left connected, the charged capacitance discharges through the input protection of the SMC30 and may latch an internal fault flag.

1. Disconnect both ends of the encoder cable before megger testing.
2. After the test, short the conductors to ground for at least 10 seconds to discharge.
3. Reconnect only after the discharge step.
4. Power the system up with the drive in commissioning mode.
5. Read r0483[0] and r2124; if a non-zero error code is still present, power-cycle the SMC30 by removing and re-inserting X521 / X522 to clear the latch.

Edge Cases and Field-Proven Caveats

• Emerson SM-Encoder Plus output format: The unit can be configured for HTL or TTL output. Many field returns show that the default HTL configuration causes the SMC30 to misinterpret the zero mark when p0430 = 0 (TTL expected). Always re-verify p0430 after switching the simulator output standard.
• Firmware V4.80 quirk: On drives running SINAMICS firmware V4.80, a transient A07565 with r0483[0] = 0x0008 appears on the very first zero mark after power-up even when wiring is correct. This is corrected by either upgrading to firmware ≥ V4.90 or by suppressing A07565 until referencing is complete.
• Double zero mark: Some encoder simulators produce a doubled zero pulse to compensate for EMC. The SMC30 debouncer in p0437[0] (filter time, typically 0.1 µs to 10 µs) may reject one of the two pulses. If r0483[0] = 0x0002 is logged on a known-good simulator, increase p0437[0] in 1 µs steps until the alarm clears.
• Mixed-parameter sets: When the project has multiple parameter sets (DDS), ensure that p0480 and p4652 are written into all active sets; otherwise the alarm returns when the drive switches DDS.

Verification and Commissioning Checklist

1. Clear the alarm buffer with p3981 = 30 (acknowledge all) or via Diagnostics > Alarms > Acknowledge on the operator panel.
2. Rotate the encoder at least one full revolution. Verify r0061[0] (speed) and the position counter r0481[0] advance smoothly without jumps.
3. Monitor r2124 live: it must remain 0 throughout one revolution, including the zero-mark event.
4. Run a controlled reference-point approach with the controller, observe r3996[0] and confirm the position is set to zero at the zero-mark crossing.
5. Repeat for 10 consecutive power cycles. No A07565 should be logged.
6. Save the project to CFast / SD card and back up to TIA Portal / Starter archive.

Frequently Asked Questions