Resolving S7-1200 Sinamics G120C PROFINET Name of Station Errors

Problem Summary

A SIMATIC S7-1200 CPU is configured as a PROFINET IO Controller for a line-up of five SINAMICS G120C PN frequency converters. On PLC startup the controllers enter RUN, the G120C run LEDs light solid green, but each drive's BF (bus fault) LED blinks red at ~2 Hz and the CPU raises a PROFINET IO device diagnostic alarm such as "IO device failure", "Station failure", or "Device name not assigned / not unique". No cyclic data is exchanged; the drives revert to the configured fallback safe state.

The dominant root cause for this symptom matrix on S7-1200 / G120C PN systems is a Name of Station mismatch between the offline TIA Portal project and the device's flash-stored PROFINET name. The drives are physically alive (run LED green), the network is wired (CPU does not raise link-down diagnostics), but the IO controller rejects the AR (Application Relationship) because the configured PROFINET device name does not match the actual name the device is announcing.

Root Cause: Name of Station vs. Device Display Name

PROFINET devices carry three different identifiers that engineers frequently confuse:

When the G120C PN is discovered online, TIA Portal shows the catalog display name (e.g., g120cpn or sinaamicsg120cpn). This is the device's PROFINET device name, not the configured Name of Station in your project. The true identifier that the IO controller uses to establish the AR is the value in the "Converted Name" field of the device's PROFINET interface → Ethernet addresses tab. PROFINET names must obey the same rules as a DNS label: lowercase a–z, 0–9, hyphen; must start with a letter; max 63 characters for the label portion (max 240 for the full station name); no underscores, no spaces.

Reference: see the SIMATIC S7-1200 Programmable Controller System Manual, section on PROFINET device name assignment, and the SINAMICS G120C Operating Instructions, chapter on PROFINET commissioning.

G120C PN LED Diagnostic Matrix

Use the drive's LED pattern to localize the fault before touching the project. The G120C PN has the following status indicators on the front of the Control Unit (CU250S-2 PN variants, e.g., 6SL3210-1KE21-3UP1 / 6SL3210-1KE22-6UP1):

The source symptom (green RUN on drive, green RDY on the drive's CU, red BF blink) is the classic Name of Station signature. If the BF is solid red, stop and check the physical layer first; if it is fast-blink red, verify the IP and subnet mask against the CPU's PROFINET interface.

Prerequisites

1. CPU 121xC, 1215C, 1217C, or 1214C with PROFINET interface (firmware ≥ V4.2 recommended for G120C PN GSD support).
2. Five SINAMICS G120C PN Control Units with matching GSDML installed in TIA Portal (e.g., GSDML-V2.34-Siemens-SINAMICS_G120C_PN-20201026.xml or newer for V4.7 SPx of the drive).
3. PROFINET device names pre-planned: g120c-1, g120c-2, g120c-3, g120c-4, g120c-5 (lowercase, DNS-label compliant).
4. Unique static IP addresses per drive in the same subnet as the CPU, e.g., CPU 192.168.0.1/24, drives 192.168.0.11–15/24.
5. Topology: direct connect star from CPU to drives, or via a managed SCALANCE switch. If direct connect, the CPU's port must not be set to "Monitored" mode in the topology editor if the cabling does not match the configured port partners.
6. TIA Portal V15.1 or newer (V12 as mentioned in the source is end-of-life and no longer accepts modern GSDMLs — upgrade strongly recommended).

Step-by-Step: Verify the Configured PROFINET Name of Station

1. Open the TIA Portal project and select the Devices & Networks view.
2. Click the first G120C PN in the network view.
3. In the Inspector window select Properties > PROFINET interface [X1] > Ethernet addresses.
4. Read the value in PROFINET → "Name of the PROFINET device (Device name)". This is the offline, project-side Name of Station. Note: the field Device name at the top of the properties page is the catalog display label, not what is on the wire.
5. Cross-check this string against the row in the project tree — both must be identical.
6. Repeat steps 2–5 for every G120C PN. Drives must have unique names — duplicates cause the controller to bind to the first matching device and leave the rest in bus fault.

Step-by-Step: Verify the Online Name of Station Stored in the Drive

1. Connect the S7-1200 to the same PROFINET subnet as the drives. The CPU is the IO controller; do not connect a programming PC in parallel through a separate unmanaged switch (avoid DCP storms on the CPU's port during assignment).
2. In the project tree right-click the CPU → Go online (or use the toolbar "Online > Accessible devices").
3. Use Online > Accessible devices to perform a network scan. TIA will list every device it hears via DCP Identify, including its real PROFINET name (the one stored in the drive's flash).
4. Compare each scanned device's "Device name" (real) with the project's "PROFINET device name" (configured) for the corresponding IP. They must match exactly. A typical mismatch in the field is the catalog display name (g120cpn) versus the configured project name (g120c-1) — TIA will show a yellow warning triangle on the online/offline compare.
5. If you cannot read the stored name, perform a PROFINET name reset on the drive using the SIMATIC automation tool or the SINAMICS Starter / Startdrive commissioning software: under the drive's PROFINET interface use Reset PROFINET name. This brings the drive back to its factory default name and is the precondition for a clean re-assignment.

Step-by-Step: Assign the PROFINET Name of Station to Each Drive

1. In the TIA Portal network view, right-click the first G120C PN → Assign PROFINET device name.
2. In the dialog set the PROFINET device name field to the exact lowercase string from the project (e.g., g120c-1).
3. Set the IP address to the static value planned in the project (e.g., 192.168.0.11) and the subnet mask to 255.255.255.0. Leave the router address empty unless an inter-network router is used.
4. Click Assign name. TIA will broadcast a DCP IdentifyReq → DCP IdentifyRes, then send a DCP SetNameAndIp, then verify with a fresh DCP IdentifyRes. A green check confirms the write.
5. Power-cycle the drive to flush the new name from volatile RAM to non-volatile flash on the CU250S-2 (PROFINET names are committed on the next save-to-flash; on G120C PN this happens automatically at the next power-down or through the Save settings action in Startdrive). Without the power-cycle the new name may revert on restart.
6. Repeat for drives 2 through 5, using the unique names g120c-2 … g120c-5.

Step-by-Step: Topology Online/Offline Comparison

PROFINET on S7-1200 uses LLDP for port-neighbor discovery. If the configured port partners do not match the real cabling, the BF LED will still blink even after the Name of Station is correct.

1. Open Devices & Networks > Topology view.
2. Click Compare offline/online in the toolbar.
3. For every port partner the topology editor highlights mismatches in red (port partner missing, partner port index wrong, or "any partner" mismatch). The most common field error on G120C PN line-ups is an incorrect neighbor port index (G120C PN has two ports, P1 and P2; index 0 vs. 1, or the CPU's port number being mis-mapped).
4. Right-click the red marker and select Apply online topology if the real wiring is what you want to keep, or fix the cabling if the project is the source of truth.
5. Recompile and download the hardware configuration. Watch the BF LED drop and the run LED on the drive go solid green within one AR-establishment cycle (typical < 3 seconds).

Verification and Acceptance Test

Use this checklist to confirm a clean fix:

• All five G120C PN BF LEDs are OFF; LNK LEDs are solid on every active port.
• CPU's diagnostics buffer shows no PROFINET IO device failure entries; "IO device OK" appears for each configured drive.
• In Online & Diagnostics of the CPU, the PROFINET IO system list shows all five devices with status = OK and AR established.
• Word IW / status word 1 (ZSW1, slot 1) reflects the drive's actual state (e.g., 0x0637 = ready, enabled, no fault) within one telegram cycle after sending control word 1 (STW1) 0x047F (pulse enable + ramp-up).
• Run a 60-second no-fault test with a small reference speed (e.g., 100 rpm), then a reversal, then an OFF1 stop. Verify ZSW1 bit-10 (control requested) toggles correctly.

Common Pitfalls and GSD Configuration

For the SINAMICS G120C PN GSD, always download the latest GSDML from the SINAMICS G120C Operating Instructions page or the Siemens Product Support search for "GSDML G120C PN". Match the GSDML to the firmware of the CU250S-2 Control Unit; mismatched GSD/firmware combinations will accept the device but fail on telegram negotiation.

Commissioning Recipe (Minimum Viable Project)

1. Insert the S7-1200 CPU, add five G120C PN devices from the device catalog (matching GSD).
2. Wire the PROFINET port of the CPU to drive #1 P1, drive #1 P2 to drive #2 P1, daisy chain to #5.
3. In the topology editor, set port 1 / port 2 partners explicitly for each cable segment.
4. Assign IPs: CPU 192.168.0.1, drives 192.168.0.11 through 192.168.0.15, mask 255.255.255.0.
5. Assign PROFINET names plc-1 / g120c-1 … g120c-5.
6. Add standard telegram 1 (PZD-2/2) for each drive and map STW1/ZSW1 to data words.
7. Compile, download, go online. Verify BF LEDs drop and ZSW1 reads 0x0637 after issuing STW1 0x047F.

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