Resolving SINAMICS S210 r46.0 Missing Enable on CU305-PN

1. Problem Overview

When commissioning a SINAMICS S210 drive cluster in a stand-alone configuration (no SIMATIC S7 or third-party PLC) using a PM240-2 Power Module, a CU305-PN Control Unit, and a 1FK7044-4CF71-1CH1 SIMOTICS S-1FK7 servo motor in Basic Positioner (EPOS) mode, the drive refuses to transition from commissioning state S2 (Ready for switching on) into S3 (Ready for operation). The expert list shows:

• r0046.0 (Missing enable / "Enable missing") = 1
• r0863 (Drive coupling status word / state machine) = 0000H (no active enable bits)
• Control Panel jog function responds correctly (proves power section, encoder, and motor are healthy)
• Program traversing blocks and hand-wheel jogging issued through the BICO-free telegram do not produce motion
• ON/OFF1 toggling has no effect even though the digital output is active

This is one of the most frequent commissioning issues on SINAMICS S210 with the Basic Positioner license, especially in stand-alone machine concepts where the PLC control word is replaced by a hand-held controller or hardwired BICO interconnection. The fault is not a hardware failure, but a missing or incorrectly wired enable signal chain.

2. Affected Components and Firmware

The 1FK7044-4CF71-1CH1 is a 4-pole, self-cooled high-dynamic servo with integrated DRIVE-CLiQ encoder, 24-bit singleturn + 12-bit multiturn resolution, holding brake (1CH1 = brake variant). The 1CH1 brake variant matters for EPOS because the holding brake must be released (p1215 = 1 or 3) before the drive will accept motion commands; the brake release itself is gated by r0046.0.

3. Enable Signal Architecture: r0046 and r0863

Parameter r0046 is the consolidated "Missing enable" display word. According to the official Siemens support article on the SINAMICS S210 missing enable signal, the value r0046 = 0 indicates that all enable signals for the drive are present. Each bit of r0046, when set to 1, identifies a specific missing enable source:

Parameter r0863 reflects the drive state coupling word driven by the SINAMICS state machine:

For the drive to leave S2 and reach S3 (Ready for operation), bits 00, 01, 02, 03 of r0863 must be 1. The most common S2 → S3 blocker when r0046.0 = 1 is a missing OFF1 — the ON command has not been issued, or it has been issued as a static level rather than a 0→1 edge.

4. Root Cause: ON/OFF1 Edge Behavior

The ON/OFF1 command is edge-evaluated by the SINAMICS state machine. The drive only accepts a 0→1 transition of the OFF1 source after all other prerequisite enables (OFF2, OFF3, inverter enable) are present. The state machine rejects a static HIGH on p840 and rejects an OFF1 edge that arrives before the other enables are HIGH. This is the precise reason a stand-alone S210 cluster remains in S2 even when the operator toggles the ON bit in the BICO-free control word or hand controller: the OFF1 edge has either never been generated, or it was generated before the other enable sources were set, in which case the drive discards it.

The typical process for a stand-alone BICO-free telegram is:

1. Set OFF2 (p844 source) = 1 — release emergency stop rail.
2. Set OFF3 (p848 source) = 1 — release fast stop.
3. Set Inverter Enable / pulse enable (p852 source) = 1 — gate the IGBT pulses.
4. Wait ≥ 50 ms so the state machine latches the enable chain.
5. Issue a positive edge on OFF1 (p840 source) — only now does the drive transition S2 → S3 → S4.
6. Then issue the EPOS jog / traversing block / MDI command.

If the user writes a fixed control word from the BICO-free telegram and only toggles the ON bit (bit 0) when the other bits are already 1, the drive will still appear to ignore the command if the OFF1 source is a DI on the CU305-PN and that DI has not been wired, is not powered, or is BICO'd to a different parameter than p840. This is the most common reason a stand-alone hand-controller commissioning hangs in S2.

5. Digital Input Wiring on CU305-PN X130 / X133

The CU305-PN exposes its digital inputs on connector X130 (DIs 0–3, fast DIs 4–5) and X133 (DIs 6–9, DI/DO bidirectional). The default BICO interconnect on SINAMICS S210 firmware assigns:

Wiring rules for CU305-PN digital inputs:

• Reference potential (M) for X130 DIs is on X130.2; for X133 DIs it is X133.6 (DI/DO common M24).
• DI input voltage range: 24 V DC nominal, 0–5 V = LOW, 11–30 V = HIGH per IEC 61131-2 type 1 / type 3.
• Each DI has an input debounce filter (p0724 default 2 ms); for fast EPOS jog inputs use DI4/DI5 with p0724 = 0 or 1.
• Bi-directional DI/DO channels (DI8/DI9) must be reconfigured from output to input with p0728.8 / p0728.9 = 0 (input). The default on SINAMICS S210 is output, which is why a technician may see the channel drive a 24 V level on the terminal but the expert list r0722.8 stays at 0 even though the line is toggled externally — the channel is still an output, and the input is not being read.

6. Step-by-Step Commissioning Procedure

The following procedure assumes a stand-alone SINAMICS S210 cluster (CU305-PN + PM240-2 + 1FK7044) being commissioned with the Basic Positioner (EPOS) license, BICO-free telegram 1, and a hand-held jog controller connected to the digital inputs.

6.1 Prerequisites

• Drive firmware ≥ V5.2 SP3 on CU305-PN (matches SIMOTICS S-1FK7 1FK7044-4CF71-1CH1 DRIVE-CLiQ topology).
• Basic Positioner license activated (verify with r7758[0] = 1).
• Commissioning tool: SINAMICS Startdrive ≥ V18 (TIA Portal) or STARTER ≥ V5.5 / SINAMICS PC Tools.
• Reference: SINAMICS S210 — Missing enable signal (r0046) support article and the SINAMICS S210 List Manual available on the Siemens Industry Online Support portal.

6.2 Restore BICO defaults and select BICO-free telegram

1. Drive offline → right-click → Restore factory settings (commissions p0010 = 30, p0970 = 1).
2. Set p0015 = 0 to release the macro selection.
3. Set p0922 = 999 (BICO-free telegram 1, default for S210 stand-alone EPOS).
4. Confirm p2038 = 1 (PROFINET interface active) and the device name matches the controller project.

6.3 Wire the enable chain on the CU305-PN

1. Wire DI0 (X130.3) to the hand-controller ON/OFF1 pushbutton (24 V to pin, M to X130.2).
2. Wire DI1 (X130.4) to the OFF2 / E-stop release contact.
3. Wire DI2 (X130.5) to the OFF3 source (default NC contact; releases when HIGH).
4. Wire DI3 (X130.6) to the pulse-enable / controller-inhibit release contact.
5. If using DI8 or DI9, set p0728.8 = 0 / p0728.9 = 0 to convert from output to input.
6. Verify each DI in the expert list: toggle the input, observe r0722.0 … r0722.9 transitions.

6.4 Configure the EPOS enable bits

6.5 Commissioning sequence

1. Run Automatic configuration with the connected 1FK7044-4CF71-1CH1 motor. Accept the encoder and motor parameters from the DRIVE-CLiQ electronic rating plate.
2. Run the motor identification (p1910 = 1) and rotating measurement (p1960 = 1) so the current controller and moment of inertia are correct.
3. Verify closed-loop control: in Control Panel, jog the motor at a reduced speed (200 rpm) and confirm smooth motion. This proves power section, encoder, and motor are healthy.
4. Close OFF2 (DI1 = 1), OFF3 (DI2 = 1), pulse enable (DI3 = 1).
5. Verify r0863 shows bits 00, 02, 03 = 1. Bit 01 (OFF1) will still be 0.
6. Issue a positive edge on DI0 (ON/OFF1 pushbutton). r0863.1 must transition 0 → 1.
7. Verify the drive leaves S2 and enters S3 (Ready for operation). r0046 = 0.
8. Apply jog inputs on DI4 / DI5 — the drive should now accelerate in the selected direction.

7. BICO-Free Telegram and Control Word Sequencing

The BICO-free telegram 1 (p0922 = 999) is the default for stand-alone SINAMICS S210 applications. It exposes:

The control-word sequence to go from S1 (Switching on inhibited) through S4 (Operation enabled) with the BICO-free telegram is:

Some hand controllers and PLC libraries send 047E → 047F (16-bit control word convention) as the ON sequence. In Siemens control-word notation, this is bit 10 = 1 (control by PLC, bit 10 of STW1) followed by bit 0 = 1 (ON). The drive ignores the control word if the "control by PLC" bit (bit 10) is 0 — a frequent cause of the "r46.0 stuck at 1" symptom on stand-alone systems that try to drive the S210 like a SINAMICS V90.

8. Verification Procedure

1. Open the expert list in Startdrive / STARTER online.
2. Confirm r0046 = 0 (or at minimum r0046.0 = 0 — OFF1 present).
3. Confirm r0863 shows the expected bit pattern for the current state (S3: bits 0,2,3 = 1; S4: bits 0,2,3,5,6,7 = 1).
4. Confirm r0052.0 (Operation enabled) = 1 in S4.
5. Confirm r0899.0 (Pulses enabled) = 1 in S4.
6. Issue a jog command via the hand controller. Verify r0063 (speed actual value) tracks the setpoint and r2521 (position actual value) increments.
7. Use the Startdrive function generator or trace to capture r0046, r0863, and r0052 simultaneously during the enable sequence. The 0→1 transitions must be in the correct order.

9. Troubleshooting Matrix

10. Field-Proven Pitfalls and Safety Notes

11. FAQ