Resolving ET 200S Event 16#73E8 and SINAMICS G120 PROFINET Failure

When a SINAMICS G120 frequency inverter drops off PROFINET inside an ET 200S / F-CPU station, the safety program diagnostics buffer on the F-CPU immediately fills with Event ID 16#73E8 – Consistency of the safety program. The drive simultaneously raises F01796 (SI CU: Wait for communication) and F08526 (PROFINET: No cyclic connection) in the Starter / Startdrive fault buffer, and the device goes "not available" in the hardware configuration. This article documents the exact diagnostic data, the underlying root cause (PROFINET device name and IP address mismatch), and the procedure that restores the F-runtime group consistency using the hardware configuration "Assign device name" function.

1. Problem Overview

A working PROFIsafe station that has been in service stops communicating with the G120. The drive becomes "not available" in the hardware configuration and the F-CPU enters its safety routine. The following symptoms appear simultaneously:

• Diagnostic buffer of the F-CPU contains a new entry with Event ID 16#73E8, category "Safety program", text Consistency of the safety program.
• The G120 appears in the hardware tree with the diagnostic status "Module not available" / "Station failure".
• Starter fault buffer on the SINAMICS G120 contains F01796 and F08526 (or the Startdrive equivalents F1796 / F8526).
• The drive may have reverted its IP configuration to 0.0.0.0 after a power-down/power-up cycle, after a firmware update, or after the MMC/SD card was pulled while powered.

Initial troubleshooting steps that do not resolve the fault:

• Replacing the PROFINET cable between the switch / ET 200S interface module and the G120.
• Replacing the ET 200S interface module (IM151-3 PN HF).
• Replacing the SINAMICS G120 Control Unit (CU240E-2 PN).
• Re-downloading the STEP 7 / TIA Portal project to the CPU and to the drive.

The fault remains because none of those actions re-bind the G120 to the PROFINET controller using the device name that the F-CPU expects.

2. Affected Hardware and Configuration

The failing configuration is a PROFIsafe station that combines an ET 200S distributed I/O sub-system with a SINAMICS G120 drive controlled by a SIMATIC F-CPU over PROFINET IO. Typical article numbers in this topology:

The G120 is configured in HW Config / device configuration as a PROFINET IO device with a slot for the standard telegram (e.g., telegram 1, PZD 2/2) and – when PROFIsafe is used – a PROFIsafe slot that maps the safety telegrams to an F-DB in the F-CPU. The PROFINET device name is the binding identifier between the controller's AR (Application Relationship) and the physical drive.

3. Diagnostic Data: Event ID 16#73E8 in F-CPU Diagnostics Buffer

The F-CPU writes Event ID 16#73E8 (decimal 29672) into its diagnostic buffer when it cannot complete the consistency check on the safety program. The event is produced by the F-runtime group and is logged in the "Safety program" or "F-runtime" event category.

Event ID 16#73E8 is not caused by a bug in the safety program itself. It is the symptom that the F-CPU cannot verify the safety program because one of its PROFIsafe/PROFINET sources is unreachable. When the G120 is "not available", the F-CPU cannot build the expected input image for the F-runtime group, the F-signature check fails, and the runtime group is forced into a safe stop with the 16#73E8 entry. Once PROFINET communication to the G120 is restored, the F-runtime group must be re-integrated (de-passivation) – this is a normal operator step in the safety program.

The mechanism for compiling and downloading a safety program in RUN mode – which is what the F-CPU is trying (and failing) to do at the moment Event 16#73E8 is logged – is documented in the SIMATIC Safety – Safety program in RUN mode (S7-1200 / S7-1500) manual. The "Consistent Compile" setting is required for the F-CPU to be able to download and re-verify the safety program without a STOP transition. When a PROFINET slave is missing, even the consistent-compile path cannot reconcile the runtime image and the 16#73E8 entry is produced.

4. SINAMICS G120 Fault Codes F01796 and F08526

While the F-CPU is logging Event 16#73E8, the SINAMICS G120 writes two corresponding faults into its own fault buffer (visible in Starter, Startdrive, or the BOP-2). The faults are linked; they describe the same problem from the drive's side of the PROFINET/PROFIsafe connection.

The numeric "3" in the Starter status string "SI CU: Wait for communication(3)" indicates the wait-state sub-status; it is a normal sub-state during PROFIsafe startup and is not by itself an error. The fault is only latched if the wait state persists beyond the PROFIsafe watchdog (default 100 ms – see parameter p9850 SI PROFIsafe monitoring time on the G120).

The two faults together are diagnostic of one underlying condition: the drive has PROFINET link (the LEDs are green) but no PROFINET IO controller is talking to it. The most common reason in a previously-working station is that the device name stored in the G120 is empty, has been overwritten, or does not match the name configured in the STEP 7 / TIA Portal hardware configuration.

5. Root Cause: PROFINET Device Name and IP Address Mismatch

PROFINET IO uses two independent identifiers to bring a device into operation:

1. IP address – required for all TCP/IP-based services (Web server, STARTER routing, OPC UA, etc.) and for the PROFINET RPC discovery used to assign the device name.
2. PROFINET device name – a unique station name (e.g., "g120-line-1") that is the primary key the IO controller uses to find the device on the network and build the Application Relationship. The device name is stored in non-volatile memory on the G120 and is not the same as the IP address.

If either identifier is missing or wrong, the controller cannot find the device and the IO AR is not established. The drive will then:

• Show an empty IP address (0.0.0.0) after a factory reset or MMC removal;
• Raise F08526 because no cyclic IO is exchanged;
• Raise F01796 because the PROFIsafe host never sends the parameterized F-telegram;
• Trigger the F-CPU Event 16#73E8 because the F-runtime group cannot read its expected PROFIsafe inputs.

Assigning an IP address without assigning a device name is a very common trap. The IP can be set correctly (e.g., via the BOP-2, via STARTER, or via a temporary primary setup tool) and the drive will still refuse to come online, because the controller looks for it by name first. The PROFINET standard specifies that the device name is the unique identifier for AR establishment; the IP address is only a transport-layer parameter.

The drive can lose its stored device name for several reasons in a previously-working station:

• The control unit was replaced with a spare that came factory-default.
• A firmware update cleared the non-volatile parameter set.
• The MMC / SD card was pulled while the Control Unit was writing.
• A power dip occurred while the controller was writing the name to non-volatile memory.
• The plant network was rescanned and another tool (e.g., PRONETA) assigned a generic name.

6. Solution Procedure: Assign Device Name from Hardware Config

Assign the device name to the G120 directly from the hardware configuration of the IO controller. This writes the configured name into non-volatile memory on the drive over the PROFINET discovery protocol (DCP). Once the name matches the project, the controller automatically establishes the AR, the cyclic IO starts, F08526 and F01796 clear themselves, and the F-CPU can re-integrate the F-runtime group.

6.1 Prerequisites

• Programming device (PG) connected to the same PROFINET subnet as the G120, either directly or through the F-CPU's routing interface.
• STEP 7 V5.5 / V5.6 with HW Config or TIA Portal V15.1 or later with the G120 HSP or GSD file installed.
• STEP 7 project open with the F-CPU hardware configuration containing the G120 and the correct device name (right-click the G120 → Properties → PROFINET interface → Ethernet addresses).
• Access to the F-CPU in STOP or RUN-P – STOP is recommended for the first assignment because it gives an unambiguous result.

6.2 Step-by-Step

1. Open the STEP 7 / TIA Portal project that contains the station.
2. In the project tree, expand the F-CPU and locate the PROFINET IO system that contains the SINAMICS G120.
3. Right-click the G120 device → PROFINET Device Name (TIA Portal) or PLC → Ethernet → Assign Device Name (STEP 7 V5.x). The exact menu path differs by version; the underlying dialog is the PROFINET DCP "Assign PROFINET device name" tool.
4. In the Assign Device Name dialog, the configured name is pre-filled (e.g., g120-line-1). Leave it as configured in the project.
5. Click Assign Name. The PG broadcasts a DCP "Set" frame to all reachable PROFINET devices. The G120 with the matching MAC address stores the name in non-volatile memory.
6. Verify the assignment: the G120 now appears with the green checkmark in the "Accessible nodes" list of the PG.
7. Power-cycle the G120 Control Unit to ensure the name is read from non-volatile memory at the next boot.
8. Download the hardware configuration to the F-CPU. The F-CPU uses the device name to build the AR; the cyclic IO and PROFIsafe come up automatically.

6.3 TIA Portal Variant

1. Open the device configuration of the G120.
2. Properties → PROFINET interface → Ethernet addresses.
3. Confirm the "PROFINET device name" field matches what you intend to assign.
4. Right-click the G120 in the network view → Assign device name.
5. Select the target device by MAC address, click Assign name.

6.4 What This Action Does Internally

The "Assign Device Name" dialog uses the PROFINET DCP (Discovery and Configuration Protocol) "Set" service to write the name into the device. The name is stored under the device's own MIB/persistent storage and is preserved across power cycles. On the next PROFINET startup the IO controller's "Connect" request matches the name, the controller establishes the AR, and the parameterized IO data + PROFIsafe telegrams start to flow.

7. Restoring Safety Program Consistency in RUN Mode

After the PROFINET connection is restored, the F-CPU has Event 16#73E8 in its diagnostics buffer and the F-runtime group is passivated. Two recovery paths exist.

7.1 Cold restart (CPU STOP → RUN)

1. Switch the F-CPU to STOP.
2. Confirm that the G120 is reachable (PROFINET diagnostics = OK).
3. Switch the F-CPU back to RUN. The F-runtime group is re-initialized and the 16#73E8 entry is closed.

7.2 Re-integration in RUN (recommended for S7-1500F / S7-1200F)

For S7-1500F CPUs (and S7-1200F with FW ≥ 4.4) the F-runtime group can be re-integrated without stopping the CPU. The procedure is described in detail in the SIMATIC Safety – Safety program in RUN mode (S7-1200 / S7-1500) documentation.

1. The "Consistent Compile" option must be enabled in TIA Portal (Project → Safety → Settings → Consistent compile).
2. Re-compile the safety program. The F-CPU verifies the F-signature and the F-source container; on a match, the F-runtime group is automatically re-integrated.
3. On an S7-300F / S7-400F, this requires a STOP → RUN because the older F-runtime architecture does not support consistent compile in RUN.

8. Verification Steps

Confirm the fix end-to-end with the following checklist:

1. G120 reachable. In TIA Portal / STEP 7 "Accessible nodes", the G120 responds with the configured device name and IP. The PROFINET "Station status" LED on the G120 is solid green.
2. No new faults in Starter. The Starter fault buffer contains no new F01796 or F08526 entries after the AR is up.
3. F-CPU diagnostics buffer clean. No new Event 16#73E8 entries appear. Existing entries remain in the buffer but are not re-emitted.
4. Cyclic IO active. In the F-CPU online view, the G120 slot shows "OK" (green) and the input / output process images are updated.
5. PROFIsafe active. In the safety program online view, the F-DB that maps the G120 PROFIsafe slot shows the F-host status VALID (bit 0 of the F-status byte is set).
6. F-runtime group re-integrated. The F-runtime group diagnostic DB reports RUN and the passivation flags are cleared.
7. Operator ACK. The HMI / operator issues the prescribed ACK to release the safety functions.

9. Preventive Measures and Commissioning Checklist

Apply the following during initial commissioning of any F-station that contains a SINAMICS G120 over PROFINET. The cost of these checks is small compared to the cost of a day lost to "module not available" diagnostics.

• Document the device name in the plant documentation. Every G120 (and every other PROFINET slave) gets a unique, project-wide PROFINET device name. The name is part of the as-built documentation, not just the engineering file.
• Avoid generic names. Names like "g120" or "drive1" are fine inside one cabinet but must be globally unique across the plant. PROFINET does not allow two devices with the same name on the same IO controller.
• Always assign device name + IP together. When restoring a drive from a project backup, use the "Assign device name" tool rather than typing the IP into the BOP-2. The IP alone is not sufficient for AR establishment.
• Enable "Consistent Compile" in TIA Portal. This allows safety program re-integration in RUN after PROFINET recovery and is required for the Event 16#73E8 path described in §3.
• Set PROFIsafe monitoring time (p9850 / p9851 on the G120) high enough to ride through a brief controller restart. Typical values: p9850 = 100 ms (default), p9851 = 100 ms. Do not exceed the value required by the risk assessment.
• Lock the BOP-2 / IOP-2 parameter write access in production to prevent accidental parameter changes.
• After every firmware update of the G120 or F-CPU, re-assign the device name and re-download the hardware configuration to the controller. Firmware updates do not always preserve the PROFINET device name across major version transitions.
• Use PRONETA or TIA Topology for periodic network audits. PRONETA (free tool from Siemens) shows all reachable PROFINET devices with their IP, name, and MAC, which makes "who is online with what name" trivial to verify.
• Keep an offline copy of the hardware configuration that includes the device name export. This is the fastest way to re-assign the name if a drive is replaced at short notice.

10. Related Diagnostic Events to Watch For

When Event 16#73E8 appears alongside the G120 PROFINET fault, also scan the F-CPU diagnostics buffer for the following related events. They often appear in the same incident.

11. Field-Proven Caveats

• PROFINET device name is case-sensitive. "G120-Line-1" and "g120-line-1" are different names. The IO controller will not match if the case differs between the project and the physical device.
• MAC address collisions break DCP. If two devices on the same subnet share a MAC (clone incident after a control unit replacement), DCP name assignment silently targets the wrong device. Always verify the MAC after a hardware swap.
• The G120 does not respond to ARP for an IP it does not have. A ping test will fail even though the PROFINET link is good. Do not use ping as the only health check.
• Starter "Go online" can succeed even with a missing device name. STARTER uses TCP/IP routing and does not require the PROFINET device name; it can connect via the IP address alone. This is why "online" in Starter does not mean PROFINET IO is up.
• Re-assigning the device name does not require a download to the F-CPU. It is a direct write to the drive. The F-CPU discovers the renamed device on its next PROFINET scan and builds a new AR.
• Event 16#73E8 entries are sticky in the diagnostic buffer. They are not automatically cleared; only the operator / engineering tool can clear them. New incidents produce new entries on top of old ones.

12. Frequently Asked Questions