Enabling Standard Telegram 5 on F-TM StepDrive FW 2.1+

Problem Description

The F-TM StepDrive (F-TM ServoDrive variant for stepper motors) is configured in a SIMATIC ET 200SP station on a PROFINET network, but standard telegram 5 cannot be selected in the drive object's properties. The available telegrams are limited to standard telegrams 1, 2, and 3, while telegram 5 — required for Dynamic Servo Control (DSC) — is greyed out or missing from the dropdown.

A typical affected configuration:

• F-TM StepDrive module, article group 6BK1, firmware V2.1 or higher
• ET 200SP Open Controller CPU 1515SP PC3, firmware V40.0 (or comparable S7-1500 CPU)
• IM 155-6 PN ST (Standard variant, 6ES7155-6AA00-0BN0 family)
• TIA Portal V20 Update 5 with the latest Hardware Support Package (HSP)
• PROFINET IRT enabled in the interface properties

The user expects DSC support because the F-TM StepDrive equipment manual explicitly lists telegram 5 as an option from firmware V2.1. Reference: F-TM StepDrive Equipment Manual (Siemens, 11/2024), section on isochronous operation.

Root Cause Analysis

The F-TM StepDrive equipment manual states the precise prerequisite for telegram 5 with DSC:

"If both the CPU (at least 1500) and the ET200SP (HF or HS) support clock synchronization, the TM Drive from firmware version 2.1 or higher can be integrated into an isochronous group."

Three independent conditions must ALL be satisfied to enable telegram 5 with DSC on the F-TM StepDrive:

1. F-TM StepDrive firmware V2.1+ — provides the DSC-capable drive object on the device.
2. ET 200SP IM 155-6 PN HF or HS head module — must support isochronous mode and clock-synchronized PROFINET (IRT with sync master capability). The ST (Standard) variant does not support isochronous real-time and therefore cannot be the sync master for the drive object.
3. S7-1500 CPU with PROFINET IRT and isochronous mode capability — e.g., CPU 1515SP PC3 (or any S7-1500 CPU that exposes an IRT-capable PROFINET interface and supports isochronous mode on the OB).

When the IM 155-6 PN ST is in the slot, the IO controller reports that the F-TM StepDrive subslot cannot be part of an isochronous group. TIA Portal filters the telegram list to telegrams compatible with non-isochronous operation, leaving only standard telegrams 1, 2, and 3. Standard telegrams 6 and 9xx are likewise absent because they also require DSC or isochronous motion control.

Hardware Requirements: IM 155-6 PN ST vs HF vs HS

Reference: ET 200SP IM 155-6 PN HF (6ES7155-6AU00-0BN0) manual and the ET 200SP IM 155-6 PN HS (6ES7155-6BA00-0BN0) manual.

Prerequisites

• TIA Portal V20 Update 5 (or later V20 HSP level); V18/V19 with current HSP is acceptable for the configuration changes but the F-TM StepDrive V2.1 device description requires V18 HSP0530 or V20.
• S7-1500 CPU with firmware supporting isochronous mode on the PROFINET interface (CPU 1515SP PC3 FW 40.0 confirmed compatible).
• IM 155-6 PN HF or HS head module; the ST variant must be physically and logically replaced.
• F-TM StepDrive, firmware V2.1 or higher (read with online diagnostics or in the module's properties).
• STEP-Motor with an incremental encoder (A/B or A/B/Z tracks).
• HSP installation path: Siemens Support entry 72341852

Step-by-Step Solution

1. Identify the head module variant. Open Devices & Networks, select the ET 200SP station, and read the order number (MLFB) on slot 0. Confirm whether it is the ST, HF, or HS variant. The order number on the front of the module must match.
2. Replace the IM 155-6 PN ST with HF or HS. In the device view, drag the new module (6ES7155-6AU00-0BN0 or 6ES7155-6BA00-0BN0) to slot 0 and accept the port interconnection. The PROFINET device name, IP, and topology are preserved.
3. Enable isochronous mode on the PROFINET interface. In Properties > PROFINET interface > Real time settings > Synchronization, activate Synchronize the IO device to the RT class and select IRT. Configure the send clock — typical values for F-TM StepDrive DSC are 1.0 ms or 500 µs; consult the drive manual for the supported set.
4. Configure the F-TM StepDrive slot for isochronous operation. Open the F-TM StepDrive in the device view, go to Properties > Module parameters > Isochronous mode, and tick Enable isochronous mode. Assign the Ti (time of input) and To (time of output) values per the drive documentation.
5. Select standard telegram 5. In Properties > Telegram configuration, set Standard telegram = 5 and Add telegram = Standard telegram 5 (or "Standard telegram 5 + DSC" depending on the GSDML entry). The PROFIdrive slot 0 / 1 structure will then become:

   Standard Telegram 5 (Positioning + DSC)
     PZD1: STW1  (control word 1, 16-bit)
     PZD2: POS_STW1 (positioning control word 1)
     PZD3: POS_STW2 (positioning control word 2)
     PZD4: STW2  (control word 2 — DSC enable)
     PZD5: MDI_TARPOS (MDI target position, 32-bit)
     PZD6: MDI_VELOCITY (MDI velocity, 32-bit)
     PZD7: MDI_ACC (MDI acceleration, 16-bit)
     PZD8: MDI_DEC (MDI deceleration, 16-bit)
     --- mirror actual values ---
     PZD9 : ZSW1 (status word 1)
     PZD10: POS_ZSW1
     PZD11: POS_ZSW2
     PZD12: ZSW2 (DSC status)
     PZD13: XIST_A (position actual value A, 32-bit)
     PZD14: NIST_B (speed actual value B, 32-bit)
     PZD15: G1_STW / G1_ZSW optional
     PZD16: XIST_A extended or DIA (depending on encoder class)

6. Assign the telegram to a technology object. In the S7-1500 axis configuration (TO_PositioningAxis / TO_SynchronousAxis), map the drive to telegram 5, then enable the Dynamic Servo Control checkbox in Configuration > Drive > Dynamics.
7. Download to the CPU and the F-TM StepDrive. Compile the project, perform a complete download (HW Config + software), and answer "Yes" to the consistency check that confirms the sync domain.

DSC (Dynamic Servo Control) Integration

DSC is a feed-forward position control loop that runs in the drive instead of in the PLC, dramatically reducing following error at high dynamics. For the F-TM StepDrive, DSC is offered from firmware V2.1 onward and requires:

• Isochronous PROFINET IRT (send clock ≤ 1 ms typical; 500 µs possible on HS head modules).
• Standard telegram 5 or a Siemens manufacturer-specific telegram containing DSC control bits (STW2.10 = DSC enable, STW2.11 = selection between Kp and Kv).
• A velocity pre-control word (NIST_B) and a position actual value (XIST_A) returned to the controller at every cycle.
• Encoder feedback on the drive, used by the internal DSC position controller.

When DSC is active, the PLC's position controller output (setpoint speed) is fed into the drive, but the drive uses its internal Kp (position gain) to compute the torque output each cycle. The PLC only generates the position setpoint; the drive closes the position loop locally.

Encoder Requirements: A/B vs A/B/Z Track

Field experience after enabling telegram 5 on the F-TM StepDrive shows that the TIA Portal configuration dialog only displays telegram 5 if an A/B/Z (three-channel) incremental encoder is selected on the drive's encoder subslot. An A/B (two-channel, no index pulse) encoder configuration does not expose telegram 5, even when the drive is otherwise isochronous-ready.

Engineering rationale for the apparent restriction:

• Telegram 5 expects an absolute or quasi-absolute position actual value (XIST_A) of at least 32 bits.
• Without a Z (index) pulse, the drive can only deliver an incremental position. After power-off, the XIST_A value is lost, and the drive cannot return a referenced absolute position to the controller on the first cycle.
• The DSC path is closed-loop on the position actual value; an unreferenced position at startup is incompatible with a high-gain internal controller.
• Some stepper encoders that are physically A/B only can be made absolute by adding a battery-buffered multi-turn counter, but the F-TM StepDrive firmware V2.1 reportedly does not expose this option for two-channel encoders in combination with telegram 5.

Hardware Support Package (HSP) Considerations

The latest HSP for the F-TM StepDrive (V2.1) is published under the umbrella entry: Support packages for the hardware catalog in the TIA Portal (HSP).

Install sequence:

1. Download the HSP ZIP from the Siemens support page.
2. Open TIA Portal, choose Options > Support Packages > Install from file system.
3. Restart TIA Portal to register the device description.
4. Verify the F-TM StepDrive appears in the hardware catalog under ET 200SP > Drive > F-TM StepDrive with firmware V2.1.0 (or higher) selectable.

If the F-TM StepDrive device description is missing or older, the Telegrams dropdown will be limited to 1, 2, 3, 102, 103, 105, etc., and telegram 5 will not appear. Always confirm the HSP version before replacing hardware.

Verification

1. Go online with the CPU. In the project tree, open Devices > F-TM StepDrive > Online & Diagnostics > Isochronous mode. The status field must report "Isochronous mode active, OK".
2. Inspect PROFINET diagnostics > Sync domain. The IM 155-6 PN HF/HS should appear as the sync master; the F-TM StepDrive should appear as a sync slave.
3. Open the technology object (TO_PositioningAxis). In the Diagnostics view, the drive should report the active telegram 5 with DSC status Active.
4. Execute a small MC_MoveAbsolute command with a velocity of 10% of the maximum. Verify the actual position follows the setpoint with no overshoot, and the following error stabilizes within the configured tolerance within two cycles.
5. Capture the cyclic PROFINET IRT frame in the topology editor and confirm the send clock matches the configured Ti / To values.

Troubleshooting Matrix

Field Commissioning Checklist

• [ ] IM 155-6 PN HF/HS physically installed; ST variant removed from slot 0.
• [ ] PROFINET topology in TIA Portal matches physical port interconnections (Port 1 of CPU X1 ↔ Port 1 of IM, etc.).
• [ ] Latest HSP installed and F-TM StepDrive V2.1 device description visible.

FAQ