SINAMICS G120 CU240E-2: Configuring Second Ramp Times via DDS

Overview

The SINAMICS G120 modular frequency-inverter family, when equipped with a CU240E-2 Control Unit (article number 6SL3244-0BB12-1BA1), supports a second set of ramp-up and ramp-down times through its drive-data-set (DDS) architecture. Each DDS carries its own copy of the ramp-function generator (RFG) parameters, so the application can switch between two completely independent acceleration and deceleration profiles - one for normal operation, one for soft-start, fast-stop, or a process-specific mode - by toggling a single digital input (typically DI2) or a single bit in the fieldbus telegram. The drive evaluates the selection every task cycle and reports the active data set in r0051.

The most common commissioning error on this topic is to place the ramp times in the Command Data Set (CDS) instead of the Drive Data Set (DDS). CDS swaps control sources, setpoint sources, and BICO interconnects; DDS swaps the motor-side and ramp-side data. The result of editing P1120 in CDS is that nothing changes at runtime, which is the symptom captured in the original field note that motivated this article. The correct path - documented below - is to keep P1120/P1121 in DDS and source the DDS bit from a digital input via BICO.

Prerequisites

Before configuring a second ramp profile, confirm the following:

• Control Unit: CU240E-2 (6SL3244-0BB12-1BA1) or a firmware-compatible variant (CU240E-2 DP, CU240E-2 PN, CU240E-2 F). All variants share the same DDS/BICO architecture described here.
• Power Module: any PM240, PM240-2, PM250, or PM260 sized for the motor. The DDS architecture is independent of the power section.
• Firmware: CU240E-2 firmware V4.4 or higher. Earlier firmware uses the same parameter numbers but the BICO list is a subset. Read the firmware version in r0018 or on the SD card label.
• Commissioning tool: STARTER V4.5 (or later) with the matching Drive ES package, or Startdrive in TIA Portal V15 (or later). Both expose the full drive-data-set and command-data-set editors.
• Motor data: motor commissioning must be complete. Set P0300/P0301 (motor type and voltage), run P1900 = 1 (motor data identification) and P1910 = 1 (rotating measurement) if the application allows. The RFG references a motor model that has been identified.
• DI2 hardware: DI2 is brought out to terminal 6 of the CU240E-2 customer terminal block (default 24 V isolated input, PNP or NPN configurable). Verify the wiring meets the digital-input electrical specification in the SINAMICS G120 with CU240B-2/CU240E-2 operating instructions.

Data Set Architecture: CDS vs DDS

SINAMICS G120 separates drive configuration into four types of data sets. Two of them are relevant to the second-ramp application:

The selection bits are binector inputs (BI) that the drive evaluates on every scan. DDS selection is encoded as a 3-bit binary number; the active DDS is reported in r0051. The active CDS is reported in r0050. If you read a parameter in the expert list, the index shown in square brackets is the data-set index - for example P1120[0] is the ramp-up time of DDS 0, and P1120[1] is the ramp-up time of DDS 1.

Parameter Reference for the RFG and DDS Selection

The following parameters are central to the second-ramp configuration. All are documented in the SINAMICS G120 with CU240B-2 / CU240E-2 operating instructions and the SINAMICS G120 parameter list.

DI2 BICO Source

On the CU240E-2, the digital-input status word is r0722. The bit assignments are fixed by the firmware:

• Bit 0: DI0
• Bit 1: DI1
• Bit 2: DI2
• Bit 3: DI3
• Bit 4: DI4
• Bit 5: DI5 (where available; some terminals are DI/DO shared)

The binector output used to feed DDS-selection BIs is r0722.0 in the BICO browser. The sub-index .0 identifies the diagnostic word; the bit inside the word is the input bit. Selecting r0722.0 from the BICO browser and then bit-routing within the downstream binector handles the bit selection.

Wiring DI2 to DDS Selection

To toggle between DDS 0 and DDS 1 using DI2, wire DI2 into P0820[0] in the active CDS:

1. In STARTER or Startdrive, open the project online with the drive.
2. Navigate to Inputs/Outputs → Digital inputs and confirm DI2 is not already assigned to a higher-priority standard function (ON/OFF1, OFF2, OFF3, acknowledge, external fault, etc.). The CU240E-2 default templates often assign DI0 = ON/OFF1, DI1 = OFF2, DI3 = acknowledge; DI2 is usually free.
3. If DI2 is already in use, pick a different free DI and adapt the steps accordingly. The BICO source for DI3 is r0722.3, for DI4 is r0722.4, and so on.
4. Open the expert list. Filter for P0820 and select the index of the active CDS. Default CDS is 0, so set P0820[0].
5. Click the BICO selection icon next to the value field. The BICO browser opens.
6. Drill into Drive unit → Control Unit → Inputs/Outputs → Status word of digital inputs. Select the binector source corresponding to the chosen DI (for DI2, this is the DI2 bit of r0722).
7. Write the parameter to the drive (online → RAM). To make the change power-cycle safe, perform a RAM-to-ROM copy.

After the BICO is set, the DDS is selected as follows:

Monitor r0051 online to confirm the active DDS follows DI2 in real time. The online watch table in STARTER (Ctrl+F11) or the Startdrive watch table is the easiest place to drop both r0051 and the relevant bit of r0722 for live monitoring.

Configuring the Second Ramp Times

Once the BICO wiring is in place, populate the second ramp values in DDS 1.

1. In the STARTER project tree, right-click Drive → Configuration → Parameter groups and open the drive-data-set editor.
2. Enable DDS 1 (and optionally DDS 2) by ticking the corresponding boxes. The CU240E-2 supports up to 3 DDS.
3. Click Drive data set 1 and enter the ramp-up and ramp-down times:
   1. P1120[1] - ramp-up time of DDS 1, in seconds.
   2. P1121[1] - ramp-down time of DDS 1, in seconds.
4. If the second slope also needs different speed limits, fill P1080[1] and P1082[1] accordingly. If different rounding is required, fill the P1130 - P1133 group.
5. Save the project offline. Click Load to drive (RAM) and verify, then Copy RAM to ROM to make the change non-volatile.

Sizing the Second Ramp

The RFG slope in P1120/P1121 is referenced to the maximum frequency P1082 of the active DDS. If P1082 changes between DDS 0 and DDS 1, the absolute Hz/s slope also changes. Use the following relation to maintain a constant Hz/s slope between profiles:

slope_Hz_per_s (DDS 1) = P1082[1] / P1120[1]
slope_Hz_per_s (DDS 0) = P1082[0] / P1120[0]

For a 50 Hz system with a 5 s default ramp and a 2 s "fast" ramp, the second DDS would carry P1120[1] = 2.0. The drive automatically references the slope to P1082[1], so unless the maximum frequency also changes, the new ramp time applies directly. The shortest permissible ramp is bounded by the current limit (P0640, default 150 % of rated motor current) and the DC-link voltage on regeneration.

Verification Procedure

1. Bring the drive to a safe state. ON/OFF1 must be OFF (terminal 0 V or control word bit 0 = 0).
2. In STARTER, open the control panel and click Assume control priority. Acknowledge any local/remote conflict warning.
3. Start the drive with a small setpoint (for example 10 Hz). Observe the ramp in the STARTER trace: time from 0 to 10 Hz should be P1120[0] * 10 / P1082[0] seconds (DDS 0 active, DI2 low).
4. Stop the drive and toggle DI2 high. Verify in the online watch table that r0051 changes from 0 to 1.
5. With the motor turning under a new setpoint step, observe the time from 0 to 10 Hz; it should now be P1120[1] * 10 / P1082[1] seconds (DDS 1 active).
6. Toggle DI2 low and confirm the ramp returns to the DDS 0 slope.
7. Disconnect the control panel, restore field control, and power-cycle the drive. Confirm both slopes persist (P1120[0] and P1120[1] are still in the ROM image).

Alternative: PLC / Telegram Control of DDS

When DI2 is not available, or the application needs more than two slopes, the DDS bit can be sourced from a fieldbus control word. Common implementations:

PROFINET with Telegram 1

Standard Telegram 1 (P0922 = 1) does not contain a DDS bit. Switch to a manufacturer-specific telegram such as 350, 352, 353, or 354, or use free telegram configuration (P0922 = 999) to add a second control word. The DDS selection bit is wired into a free bit of the second PZD word and routed via BICO.

PROFINET with Telegram 20

Telegram 20 contains the standard control word 1 and status word 1. Append the free telegram with the DDS bit mapped to a free bit of the appended word. The PLC writes the bit, the drive evaluates the BICO source connected to the receive-word bit (r2090.x).

PROFIBUS with PZD Extension

On the CU240E-2 DP variant, use P0922 = 999 (free telegram) and add the DDS selection bits to a free PZD word. In the PLC, write the DDS bit to bit 0 of the chosen word, and BICO-connect the binector input in the drive to r2090.x where x is the bit position.

S7 PLC with SINA_SPEED or DriveLib Blocks

The Siemens SINA_SPEED function block (part of the SINAMICS blocks library in TIA Portal) includes a DDS_Out word. Connect bit 0 of DDS_Out to the drive's DDS bit-0 binector. The drive selection follows the PLC state without any digital-input wiring. The block is documented in the Startdrive / DriveLib help integrated with TIA Portal.

When DDS is sourced from the fieldbus, remove the DI2 BICO wiring on P0820 (set P0820[0] = 0) and write the new binector source to the relevant bit of the receive word. The data-set update is synchronized to the fieldbus cycle and is deterministic with respect to PROFIsafe or PROFINET IRT cycle time.

Runtime RFG Scaling vs Fixed DDS

For applications that need a continuous, scalable second slope (for example, a soft-start that adapts to load, or a process where the second slope is a function of measured torque), the RFG ramp times can be multiplied at runtime using a BICO scaler on the RFG time. The method is documented in the official Siemens support entry SINAMICS G120: scaling the ramp-function generator times in operation. This is the right path when the application needs the second slope to be a percentage of the first or to be computed by the PLC each cycle. For a fixed, deterministic second slope (the typical use case for "second ramp-up/ramp-down via DI2"), the DDS approach is simpler, faster, and fieldbus-independent.

Troubleshooting Matrix

Commissioning Checklist

• CU240E-2 firmware version confirmed ≥ 4.4 (read r0018 or check the SD card).
• Motor commissioning complete (P1900 = 1; P1910 = 1 for rotating measurement if the application allows).
• DDS 1 enabled in the drive-data-set editor; the DDS bit appears in r0051 when toggled.
• P0820[0] BICO-connected to the chosen DI bit of r0722.
• P1120[0] and P1121[0] set to the default profile.
• P1120[1] and P1121[1] set to the second profile.
• Optional: P1130[0..1], P1131[0..1], P1132[0..1], P1133[0..1] rounding configured for both slopes.
• Online trace of P1120, r0051, and the relevant r0722 bit captured during the DI transition.
• RAM-to-ROM copy completed.
• Power-cycle test: both slopes persist after the 24 V supply is removed and restored.

FAQ