SINAMICS G120 CU250S-2: Telegram 352 for Current and Torque

SINAMICS G120 CU250S-2: Configuring Telegram 352 for Actual Current, Torque, and Power

The SINAMICS G120 modular drive family paired with the CU250S-2 Control Unit supports Siemens' free PROFIdrive telegram 352, which extends the two-word default Telegram 1 with the additional process data words IAIST (actual current), MIST (actual torque), PWR_A (actual power), and MELDW (message / warning word). When Telegram 352 is enabled in TIA Portal or STARTER, the actual speed in PZD2 typically starts updating immediately because the firmware ships with the BiCo interconnections for status word and speed wired by default. PZD3 through PZD6, however, stay at zero in roughly nine out of ten first-time commissioning attempts. The root cause is almost always that p922 in the drive still reads 1, or that the BiCo connectors feeding the supplementary words (p2051[2..5]) were never re-wired when the telegram was changed.

This reference walks through the exact PZD layout, the parameter set that must be re-asserted, the TIA Portal / Startdrive commissioning sequence, the equivalent STARTER path, the S7-1200 / S7-1500 PLC program, and the verification checks that confirm IAIST and MIST are arriving on the controller. It is written for engineers commissioning PM240-2, PM240P-2, or PM250 power modules with a CU250S-2 PN (PROFINET) or CU250S-2 DP (PROFIBUS) Control Unit on firmware V4.7 SP5 or higher.

Telegram 352 PZD Layout

Telegram 352 is a Siemens-specific free telegram, not a PROFIdrive application-class standard. It is activated by setting p922 (or p0922) = 352 in the drive and selecting the same telegram in the controller's device configuration. The layout is fixed once the telegram is selected; free-telegram editing tools should not be used unless a custom layout is genuinely required.

The complementary setpoint direction (PLC → drive) is also six words wide when Telegram 352 is selected, even though only the first two are pre-wired (control word 1 and speed setpoint A):

Drive-Side Parameters to Verify

The following parameter set must be inspected online after every telegram change. The values in the right column are what you should see when Telegram 352 is correctly active.

The connector numbers used in the BiCo editor are the r-parameter index offsets used internally by the drive firmware. For diagnostic writes from the expert list, the relevant numbers are:

Commissioning Sequence (TIA Portal / Startdrive)

Prerequisites

• SINAMICS G120 power module (PM240-2 / PM240P-2 / PM250) with CU250S-2 PN or CU250S-2 PN F (PROFIsafe variant), firmware V4.7 or later
• TIA Portal V15.1 + HSP or later with the Startdrive option installed
• S7-1200 (CPU 1214C / 1215C / 1217C) or S7-1500 firmware V2.0 or later
• PROFINET topology with a device name and IP assigned to the drive
• Basic speed control via Telegram 1 confirmed working (motor turns, status bits update)

Step-by-Step Procedure

1. Open Devices & Networks in the TIA project and place the G120 on the PROFINET subnet. Match the device name and IP to what the drive will use at runtime.
2. Select Telegram 352 in the device view. With the G120 selected, navigate to Properties → Device configuration → Telegram configuration and change the slot from Telegram 1 to Telegram 352. The slot expands from 2 to 6 input words. Do not use the free telegram editor unless you need a non-standard layout.
3. Compile and download the hardware configuration to the S7 CPU. The download writes the IO start address (e.g., 256) and the slot assignment to the controller.
4. Connect online to the drive via the PROFINET interface. Open the watch list and confirm that p0922 reads 352. If it still reads 1, the device-view change did not propagate; return to step 2 and check the slot configuration.
5. Save to ROM: in the online menu choose Copy RAM to ROM (or write p0977 = 1). The telegram selection is lost at the next power cycle if this step is skipped.
6. Power-cycle the drive. This is mandatory on CU250S-2 firmware below V4.7 SP10. On V4.7 SP10 and later the telegram is hot-swapped, but a clean restart is still recommended during commissioning to clear transient BiCo states.
7. Verify p2051[0..5] in the parameter view. Expected: r2089[0], r0063, r0068, r0080, r0082, r2089[1]. If p2051[2..4] are still 0, force-write them with the snippet above.
8. Test the link by enabling the drive from the PLC (control word 1 = 0x047E then 0x047F) and watching the input PZD in an S7 watch table. PZD3 (IW base + 4) and PZD4 (IW base + 6) should now show non-zero values consistent with the running motor.

The Siemens FAQ on Telegram 352 for SINAMICS G120 covers the same procedure from the legacy support portal; the Startdrive online help (SINAMICS G120 with CU250S-2 in TIA Portal) provides the modern menu path.

Commissioning Sequence (STARTER)

STARTER is still used with S7-300 / S7-400 systems and with older S7-1200 firmware that predates Startdrive support. The menu paths differ, but the parameter-level outcome is identical.

1. Open the project and double-click the G120 to open the drive object.
2. Click Connect to target system. Confirm the connection is established (green check next to the device).
3. In the navigation tree choose Communication → PROFIdrive telegram and change the selection to 352. Click Change.
4. Click Load to PG then Load to drive. Wait for the upload to complete.
5. Right-click the drive and choose Copy RAM to ROM (or write p0977 = 1). This is required for p0922 to survive a power cycle.
6. Disconnect from the drive and cycle the 24 V control power (or the line input for a standalone drive).
7. Reconnect, navigate to Commissioning → Parameter list, and verify p2051[0..5]. Force-write p2051[2..4] if they show 0.

The SINAMICS G120 List Manual documents p0922, p2050, and p2051 in detail; the parameter help text in STARTER shows the same content.

PLC Program Reference (S7-1200 / S7-1500)

Once Telegram 352 is selected in the device view, TIA Portal automatically creates input and output tags. The exact tag name depends on the IO start address and the device name; the canonical pattern uses the symbolic names Drive.Inputs.IWx and Drive.Outputs.QWx.

Structured Text (SCL) — drive telemetry block

// FB100 "Drive_Telemetry", Instance DB "iDrive_Telemetry"
// Symbolic IO: Drive.Inputs.IW256..IW266 (6 input words, base 256)
//              Drive.Outputs.QW256..QW266 (6 output words, base 256)

#Current_A  := INT_TO_REAL(Drive.Inputs.IW260) / 100.0;  // r0068 [0.01 A]
#Torque_Nm  := INT_TO_REAL(Drive.Inputs.IW262) / 100.0;  // r0080 [0.01 Nm]
#Power_kW   := INT_TO_REAL(Drive.Inputs.IW264) / 100.0;  // r0082 [0.01 kW] when r2004 = kW
#Speed_rpm  := INT_TO_REAL(Drive.Inputs.IW258);          // r0063 [rpm], integer scaling

// ZSW1 bit decoding
#DriveReady       := Drive.Inputs.IW256.%X0;  // Bit 0
#OperationEnabled := Drive.Inputs.IW256.%X2;  // Bit 2
#FaultPresent     := Drive.Inputs.IW256.%X3;  // Bit 3
#WarningActive    := Drive.Inputs.IW256.%X7;  // Bit 7
#SpeedActualValid := Drive.Inputs.IW256.%X14; // Bit 14 (n_act matches n_set)

// Fault word from MELDW (PZD6)
#MeldWord         := WORD_TO_INT(Drive.Inputs.IW266);

Ladder (FBD) — equivalent scaling

// IW260 → Current in Amps
L   "Drive".Inputs.IW260
ITD
DTR
/R  1.000000e+002
T   "Telemetry".Current_A

// IW262 → Torque in Nm
L   "Drive".Inputs.IW262
ITD
DTR
/R  1.000000e+002
T   "Telemetry".Torque_Nm

// IW264 → Power in kW (verify scaling with r2004)
L   "Drive".Inputs.IW264
ITD
DTR
/R  1.000000e+002
T   "Telemetry".Power_kW

Scaling reference formulas

The drive returns integer values; the engineer divides by the appropriate factor to obtain engineering units:

Verification Procedure

1. Confirm p0922 in the drive online. It must read 352. A value of 1 means the controller's slot configuration has not propagated; redo the device-view selection and re-download.
2. Inspect p2051[2..4]. The values must be r0068, r0080, r0082. If any is 0, the BiCo was not auto-assigned. Force-write the values from the snippet above and re-run Copy RAM to ROM.
3. Read r0068 directly in the drive parameter view. Compare it to the value arriving in IW260 on the PLC. A match confirms end-to-end correctness.
4. Check r2051[0..15] in the drive. This is the actual I/O image the drive is transmitting. r2051[2] should match r0068; r2051[3] should match r0080; r2051[4] should match r0082.
5. Enable the drive and read the PLC tags. With a 100 rpm setpoint, IW258 should be ~100, IW260 should be 0.5–3.0 A on a 1.5 kW motor, and IW262 should be 0.1–2.0 Nm.
6. Sanity check the MELDW word. Pull a known warning (e.g., trigger A09107 by exceeding p2177) and confirm the corresponding bit in IW266.

Troubleshooting Matrix

Telegram 1 vs Telegram 20 vs Telegram 352

Engineers often conflate Telegram 1, Telegram 20, and Telegram 352. They are functionally distinct and serve different purposes:

Telegram 20 is the correct choice for PROFIdrive-class applications requiring standardized status word 2 and the supplementary speed word. Telegram 352 is the correct choice when you specifically need actual current and torque feedback without the PROFIdrive-standard status word 2 — for example when the PLC is a third-party controller that does not consume ZSW2 / NIST_B. The failure mode described in this article (PZD3–PZD6 = 0) is specific to Telegram 352 because it is the only one of the three whose BiCo is not fully re-wired by the firmware on activation.

Local Verification on the BOP-2 / IOP-2

When the PLC is not yet available, the BOP-2 or IOP-2 operator panel on the CU250S-2 can be used to verify that the drive is producing the expected process data. The IOP-2 has a dedicated PROFIdrive telegram menu; the BOP-2 requires manual navigation.

BOP-2 path

1. Press OK to enter the menu.
2. Use the arrow keys to navigate to Parameters and press OK.
3. Scroll to p0922 and press OK. The display should read 352.
4. Back out and inspect p2051[0..5] one index at a time. The display shows the connector number, not the r-parameter name — expected values: 899, 0 (NIST_A is pre-decoded as 0 on the BOP-2 but is actually r0063), 268, 512, 770, 974.
5. Use Extras → Signal view to display r0068 (current) and r0080 (torque) in real time. The drive will update these even when Telegram 352 is not active, so they confirm the drive-side data is present.

IOP-2 path

The IOP-2 has a wizard under Commissioning → Communication → Telegram that walks through the same steps. It also has a Diagnostics → Cyclic data page that shows the raw PZD words being sent to the controller — useful for confirming that the drive is transmitting non-zero IAIST/MIST values even when the PLC is not yet reading them.

Third-Party Controllers (Allen-Bradley, Beckhoff, Schneider)

PROFINET controllers from vendors other than Siemens see the G120 CU250S-2 PN as a PROFINET IO device driven by the SIEM8170.GSD file. Telegram 352 is supported in the GSD; the device exposes a slot with 6 input words and 6 output words. The configuration differs by vendor:

PROFIsafe-equipped CU250S-2 PN F variants use a separate PROFIsafe slot for safety telegrams (typically 30, 31, or 901). Telegram 352 remains in the standard cyclic IO slot and does not interfere with PROFIsafe. The MELDW word (PZD6) carries the standard PROFIdrive message word, not the PROFIsafe diagnostics; for STO/SS1/SLS diagnostics over PROFINET, read the PROFIsafe slot instead.

Quick-Start Checklist

• [ ] Telegram 352 selected in Devices & Networks (TIA Portal) or Communication → Telegram (STARTER)
• [ ] Hardware configuration compiled and downloaded to the S7 CPU
• [ ] p0922 reads 352 on the drive
• [ ] p2051[2] = 268, p2051[3] = 512, p2051[4] = 770, p2051[5] = 974
• [ ] Copy RAM to ROM executed (p0977 = 1)
• [ ] Drive 24 V control power cycled
• [ ] IW base + 4 (current) and IW base + 6 (torque) update in the S7 watch table
• [ ] p0010 = 0 and p0009 = 0 on the drive
• [ ] Third-party PLC: 6-word slot mapped in the controller's IO configuration
• [ ] PROFIsafe (if used) configured in a separate slot, not in PZD6