1. Overview
The Siemens SINAMICS G120 modular drive family is one of the most common general-purpose inverters in factory automation. The Control Unit CU240E-2 (firmware ≥ V4.4 for the FPBA / PN variants) supports multiple setpoint sources — fixed internal setpoints (p1001–p1015), analog inputs, motor potentiometer, fieldbus (PROFINET, PROFIBUS, EtherNet/IP), and a configurable ramp-function generator.
This reference covers a recurring field scenario: the application requires two preset speeds plus a continuously variable 4–20 mA process setpoint. Because the G120 only accepts one main setpoint per active command data set, the clean solution is to switch between two Command Data Sets (CDS) via a digital input. CDS 0 selects the fixed-speed path; CDS 1 selects the analog-input path. This avoids the limitations of trying to combine all sources into one configuration.
2. Prerequisites
- SINAMICS G120 with Control Unit CU240E-2 (any variant: CU240E-2, CU240E-2 F, CU240E-2 PN, CU240E-2 DP) — verify on the nameplate.
- Power Module PM240-2 (or PM250, PM260) sized for the motor.
- Commissioning tool: SINAMICS Startdrive (TIA Portal V15.1+), STARTER (legacy), or IOP-2 Intelligent Operator Panel.
- Wiring: 24 V DC control supply, shield-terminated analog cable, two free digital inputs (DI 3 and DI 4 recommended).
- Motor nameplate data: V, Hz, A, kW, cos φ, rpm, connection (star/delta).
- Application limits: minimum/maximum speed (p1080/p1082), ramp times (p1120/p1121).
3. Setpoint Architecture on the G120
The G120 setpoint chain consists of three logical stages:
- Setpoint source — fixed setpoint (p1001–p1015), analog input, motor potentiometer (p1030–p1040), fieldbus, or PID output.
- Main / additional setpoint — selected via p1070 (main) and p1075 (additional). Final value = main + additional (sign convention per p1076).
- Setpoint processing — minimum/maximum (p1080/p1082), ramp-function generator (p1120/p1121), speed controller.
| Parameter | Meaning | Typical values |
|---|---|---|
| p1000[0..n] | Setpoint source selection, CDS0 | 0 = Factory default (analog + fixed), 1 = Motor potentiometer, 2 = Analog, 3 = Fixed setpoint, 4 = PROFIBUS/PROFINET, 5 … |
| p1000[1..n] | Setpoint source selection, CDS1 | Same options as CDS0 |
| p1070[0..n] | CI: Main setpoint (connector input) | BICO source — e.g. r0755[0] for AI0, r1024 for fixed |
| p1075[0..n] | CI: Additional setpoint | BICO source |
| p1076[0..n] | Scaling of additional setpoint | 1 = +, -1 = −, 2 = ×, 3 = ÷ |
4. Command Data Sets (CDS) — Why They Are Required Here
A Command Data Set (CDS) is a parameter set containing all binary and setpoint-source parameters. The G120 supports up to 4 CDS (p0170). Each CDS has its own index for p1000, p1070, p1075, digital-input BICO, etc. Switching is performed via:
- Digital inputs BICO-mapped to p0810 (CDS bit 0) and p0811 (CDS bit 1).
- Control word bits from PROFIBUS/PROFINET (bit 15/14 → p2080[14], p2080[15]).
| p0811 (bit 1) | p0810 (bit 0) | Active CDS |
|---|---|---|
| 0 | 0 | CDS 0 |
| 0 | 1 | CDS 1 |
| 1 | 0 | CDS 2 |
| 1 | 1 | CDS 3 |
5. Hardware Wiring (CU240E-2)
The CU240E-2 control-unit terminal strip (typical):
| Terminal | Function | Use in this application |
|---|---|---|
| 3, 4 | 24 V out / 0 V | Supply for sensors |
| 5, 6 | DI 0 / DI 1 | ON/OFF1, OFF2 (drive commands — keep free) |
| 7, 8 | DI 2 / DI 3 | DI 3 = p0810 (CDS bit 0) |
| 16, 17 | DI 4 / DI 5 | Optional reverse / fault acknowledge |
| 10, 11 | AI 0+ / AI 0− | 4–20 mA process setpoint |
| 12, 13 | AI 1+ / AI 1− | Optional (e.g. PID feedback) |
| 14, 15 | AO 0+ / AO 0− | Speed output to PLC/HMI |
| 1, 2 | DO 0 NC/NO | Fault relay |
Wiring topology (inline SVG, schematic only):
6. Fixed-Setpoint Parameterization
The G120 supports up to 15 fixed setpoints (p1001–p1015). Each fixed setpoint is activated by a binary combination on the digital inputs assigned to p1016 (bit 0), p1017 (bit 1), and p1018 (bit 2). For two fixed setpoints only p1016 is needed.
| Parameter | Value (example) | Description |
|---|---|---|
| p1001[0..3] | 300 rpm (CDS0) / 300 rpm (CDS1) | Fixed setpoint 1 |
| p1002[0..3] | 1200 rpm (CDS0) / 1200 rpm (CDS1) | Fixed setpoint 2 |
| p1003[0..3] | 0 rpm (disable) | Fixed setpoint 3 (unused) |
| p1016[0..3] | 722.0 (DI0) | Fixed-setpoint bit 0 source |
| p1017[0..3] | 0 (always 0) | Fixed-setpoint bit 1 source |
| p1018[0..3] | 0 (always 0) | Fixed-setpoint bit 2 source |
| p1020[0..3] | 0 | Direct selection of fixed setpoint (binary-coded) |
| p1021[0..3] | 0 | Direct selection bit 1 |
| p1022[0..3] | 0 | Direct selection bit 2 |
7. Analog-Input Parameterization (4–20 mA)
| Parameter | Setting | Meaning |
|---|---|---|
| p0756[0] | 2 | AI0 type: 0 = unipolar 0–10 V, 1 = unipolar 0–20 mA, 2 = unipolar 4–20 mA |
| p0757[0] | 4.000 | x1 of scaling — 4 mA in V equivalent (for AI scaling inside CU) |
| p0758[0] | 0.000 % | y1 — normalized at x1 |
| p0759[0] | 20.000 | x2 — 20 mA in V equivalent |
| p0760[0] | 100.000 % | y2 — normalized at x2 |
| p0761[0] | 4 mA | Wire-break threshold (only effective for 4–20 mA type) |
| p1070[1] | r0755[0] | Main setpoint = AI0 normalized (%) |
| p1080[0..3] | 0 rpm | Min speed |
| p1082[0..3] | 1500 rpm (motor rated) | Max speed |
| p2000 | 1500 rpm | Reference speed (sets 100 % for p0759/76 → p1082 ratio) |
The AI0 normalized value r0755[0] is a percentage (0 % to 100 % for 4–20 mA). It is then rescaled by the setpoint normalization to physical rpm via p2000 (reference speed). For example, 12 mA → 50 % r0755 → 50 % of p2000 = 750 rpm.
8. Configuring the Two CDS
The complete parameter plan for the requested behaviour:
| Parameter | CDS0 value | CDS1 value | Description |
|---|---|---|---|
| p1000[0] / p1000[1] | 3 (fixed setpoint) | 2 (analog) | Setpoint source selector |
| p1070[0] / p1070[1] | r1024 (fixed setpoint) | r0755[0] (AI0) | Main setpoint BICO |
| p1075[0] / p1075[1] | 0 | 0 | No additional setpoint |
| p1016[0] / p1016[1] | r0722.0 (DI0) | 0 (unused in CDS1) | Fixed-set bit 0 |
| p1001[0] / p1001[1] | 300 rpm | 0 rpm | Fixed 1 |
| p1002[0] / p1002[1] | 1200 rpm | 0 rpm | Fixed 2 |
| p0840[0] / p0840[1] | r0722.0 (DI0) | r0722.0 (DI0) | ON/OFF1 command |
| p0810[0..3] | r0722.3 (DI3) | — | CDS bit 0 |
9. Step-by-Step Commissioning
The following procedure uses SINAMICS Startdrive in TIA Portal; STARTER and IOP-2 follow analogous navigation.
- Project setup. Insert G120 with the correct order code (e.g. 6SL3210-1PE21-8UL0). Confirm the detected CU240E-2 firmware version under Device → Properties → Device Information. Update to ≥ V4.7 if available via the Siemens support portal.
- Drive wizard — basic commissioning. Run the Drive Wizard: enter motor data, choose application class Standard Drive Control (0) or Dynamic Drive Control (1), set motor identification = identify at standstill only first (p1900 = 1), then later static+rotating (p1900 = 3) if the load permits.
- Set speed limits. p1080 = 0 rpm, p1082 = motor rated speed. p1120 (ramp-up) = 5 s, p1121 (ramp-down) = 5 s. p2000 = motor rated speed (reference for AI scaling).
- Configure digital input DI0 (ON/OFF1). p0840[0] = r0722.0 (default). p0840[1] = r0722.0 (mirror ON/OFF1 to both CDS).
- Configure DI3 as CDS selector. p0810[0] = r0722.3. This makes DI3 HIGH = CDS1, LOW = CDS0. No further switching needed for a 2-CDS application.
- Configure CDS0 — fixed setpoints. p1000[0] = 3. Set p1001[0] = 300, p1002[0] = 1200. Assign p1016[0] = r0722.1 (DI1) for fixed selection. Optionally use DI0 = p1016 if DI1 is reserved.
- Configure CDS1 — analog input. p1000[1] = 2. Set p1070[1] = r0755[0]. Configure p0756[0] = 2 (4–20 mA). Move DIP switch SW1 on the CU to the I position.
- Save RAM → ROM. Click Copy RAM to ROM on the drive. Power-cycle if a green "data is only in RAM" indicator remains.
- Accept active commissioning. Use the drive display or r3996 to verify the active CDS. r0050.0 reports CDS0 active; r0050.1 reports CDS1 active.
10. Verification
Run the following checks before declaring the drive ready:
- CD toggling. With DI0 LOW (no run), set DI3 LOW, read r0050 → bit 0 should = 1. Set DI3 HIGH, read r0050 → bit 1 should = 1.
- Fixed setpoint path. DI3 LOW, DI1 LOW, issue ON (DI0 high). Drive should ramp to 300 rpm. DI1 HIGH, ON → ramp to 1200 rpm.
- Analog path. DI3 HIGH, inject 4 mA, ON → 0 rpm. Inject 12 mA, ON → 750 rpm. Inject 20 mA, ON → 1500 rpm.
- Wire break. Open the 4–20 mA loop with the drive in CDS1 and ON. Expect F03505 (AI0 wire break) or F03506 within ~50 ms, depending on p0761[0] settings.
- Fieldbus cross-check (if PROFIsafe/PN). If the drive is in PN control, verify p2080[15..14] are not overriding p0810/p0811 unintentionally. Set p2080[15..14] = 0 if unused.
11. Troubleshooting Matrix
| Symptom | Likely root cause | Remedy |
|---|---|---|
| Drive stays at 0 rpm in CDS1 | AI0 DIP switch in voltage position, or p0756 ≠ 2 | Set SW1 to I; p0756[0] = 2 |
| Fixed setpoint ignores DI state | p1016 not indexed to active CDS, or p1020 set instead of p1016 | Use p1016 (binary-coded); p1020/p1021/p1022 are direct-select (one DI per fixed) |
| CDS does not switch with DI3 | p0810 indexed wrong CDS, or DI3 BICO source incorrect | p0810[0] = r0722.3; verify DI3 LED on CU lights |
| F03505 wire-break with 4 mA present | Shield grounded at both ends → ground loop | Ground shield at drive end only; install signal isolator |
| Speed overshoots when switching CDS | Active setpoint jumps from one value to another | Stop drive (OFF1) before changing DI3; or use p1142 = 1 to freeze ramp output |
| Acknowledge CDS0 after p0810 toggled does not commit | RAM only, not copied to ROM | "Copy RAM to ROM" then power cycle |
| Fault F08501 (PROFIsafe) blocks CDS switch | Safety function active; SS1/STO prohibiting run | Resolve F08501 first — STO overrides p0810 interpretation |
12. Edge Cases and Field-Proven Caveats
- Live CDS switching while running: changing p0810 with the drive at non-zero speed produces a step change in the setpoint source. The ramp-function generator does not smooth between sources. Best practice is OFF1 → wait 0 ms → switch CDS → ON again. If continuous run is mandatory, ramp to 0 via p1142 first.
- Analog setpoint while not in CDS1: in CDS0 the AI0 remains active in hardware (the input continues to be sampled), but r0755 is not used in p1070[0]. Disabling p0756[0] in CDS0 is not supported; you must ensure the BICO chain ignores it.
- PROFINET/PROFIBUS controllers overriding p0810: when using a higher-level controller (e.g. S7-1500), the fieldbus control word bits 14/15 can be the controlling source for p0810/p0811. To retain digital-input control, set p2080[14] = 0 and p2080[15] = 0.
- CDS count exceeding 2: only the index [0] and [1] rows are needed for 2 CDS. Do not change p0170 above 2 unless explicitly using CDS2/CDS3.
- Different ramp-up times per CDS: p1120/p1121 are indexed [0..n]. If ramp time differs between fixed and analog mode, set p1120[0] = 5 s, p1120[1] = 10 s.
- Drive Data Set (DDS) vs CDS: DDS swaps motor data (motor parameters, ramp rates). CDS swaps command/setpoint-source parameters. They are independent — p0820/p0821 select DDS; p0810/p0811 select CDS.
13. Reference State Diagram (Active CDS)
14. FAQ
Can I select fixed setpoint OR analog input with the same CDS instead of using CDS switching?
No. Only one main setpoint source can be active per CDS (p1000[k] is a single enum). To switch between fixed and analog, use a second CDS via p0810/p0811 or remap p1070 with a BICO selector — the CDS method is the documented, supported path.
What digital input on the CU240E-2 should I use for CDS selection?
Any free DI can be mapped. BICO p0810 = r0722.x where x is the DI number. DI3 is commonly reserved for this; DI0 is typically ON/OFF1, DI1 is often OFF2/fixed-select. Keep DI0 and DI1 free for drive commands unless hardware constraints require otherwise.
Why does the drive stay at 0 rpm when I inject 4 mA?
4 mA corresponds to the scaled minimum (y1 = 0 % by default in p0758[0]). If the live zero must yield a non-zero setpoint, set p0758[0] to a negative percentage (e.g. −100 %) so that 4 mA → −100 % and 20 mA → +100 %, then bias accordingly with p1075.
Does switching CDS lose the running state of the ramp generator?
No — the ramp-function generator (p1120/p1121) continues from its current output, but the input setpoint source changes instantly. For smooth transitions, issue OFF1 first, switch CDS, then ON. The p1142 ramp-output freeze bit can also be used.
How many CDS does the CU240E-2 actually support?
Up to 4 (p0170). Index [0..3] is exposed on most command parameters (p1000, p1070, p0840, p0810). The DDS count is set via p0180 and is independent of CDS.