Resolving PROFINET RPC Error 16#1C010003: S7-300 to KUKA KRC4

1. Problem Overview

An S7-314C-2 PN/DP controller cannot establish a productive PROFINET IO (PN-IO) connection to a KUKA KRC4 robot controller. The PLC sees the robot as a reachable node (DCP/ping succeed and the device name resolves in HW Config), but every configured slot is reported with the diagnostic text Conflict: RPC error message (16#1C010003). No cyclic IO is exchanged between the SIMATIC CPU and the robot, which is the typical symptom when the KRC4 still operates as a PROFINET controller for other remote IO stations and the SIMATIC engineer has also assigned the same KRC4 as a PN-IO device without enabling the device stack in the KUKA project.

The error is recoverable in the field without firmware changes on either side. The root cause is not a defective Ethernet interface, a wrong topology, or an IP collision. It is a role/configuration mismatch in the KUKA WorkVisual project: the KRC4 is online as a PROFINET IO controller (for its own distributed stations, e.g., valve manifolds or remote I/O on the robot cell) but has not been told that it must simultaneously present a PROFINET device interface toward the S7-300.

2. Affected Hardware and Firmware

3. Root Cause: The PROFINET Role Conflict

PROFINET distinguishes three roles on a single physical network:

1. IO Controller – the master that owns the AR (Application Relationship) and issues cyclic IOCR (IO CR).
2. IO Device – the slave that exposes slots and subscribes to the controller's IOCR.
3. IO Supervisor – a diagnostics / engineering station (e.g., a laptop running STEP 7 or TIA Portal).

A KRC4 can be loaded with a PROFINET stack in either role, or both (in newer KSS versions). The default for a freshly imported WorkVisual project is often PROFINET controller – the KUKA project is created with a virtual PROFIsafe/PROFINET subnet that controls the KRC4's own remote I/O (valve terminals, conveyor sensors, safety peripherals, etc.). When a separate SIMATIC S7-300 project is then built and the KRC4 is also placed in HW Config as a PN-IO device, the KRC4 firmware does not know it must answer the S7-300's DCP Identify & Set-Property requests, because the device stack has not been activated in the WorkVisual project.

The result at the controller side is that the AR cannot be established. Siemens' diagnostic buffer translates this into a standardized PROFINET alarm:

4. Error Code 16#1C010003 Decoded

The diagnostic block 16#1C010003 is a PROFINET channel diagnostic. Its structure under Siemens PROFINET diagnostics – entry ID 109758504 is:

Reading the same alarm in STEP 7 under PLC → Diagnostics/Setting → Module Information → IO Device Diagnostics shows "Conflict: RPC error message (16#1C010003)". This is a generic AR-Add failure. The most common field causes, in order of frequency, are:

1. Device stack not activated on the KRC4 (this article).
2. Device name assigned in HW Config but not written to the KRC4 via DCP (the KRC4 keeps the empty/factory name; the AR is rejected because the station name does not match).
3. Mismatch in the expected slot count / module configuration between the GSD and the KRC4 project (e.g., the KRC4 publishes 2 input / 2 output words but the SIMATIC project expects 8/8).
4. Wrong AR properties – specifically the KRC4 firmware rejects the AR because of an IOCR with an unsupported send clock or a Watchdog factor of 0.

Items 2-4 should always be checked, but in the scenario this article documents, item 1 is the actual fault. Ping/ARP success and a successful DCP Identify (you can read the device name back in HW Config) rule out 2, while 3 and 4 produce a different error class (typically 16#1C020001 – "Invalid slot configuration"). The 0x1C01 family points cleanly at the AR handshake, which is where the missing device stack manifests.

5. Prerequisites for Resolution

• STEP 7 V5.5 with current Hardware Support Package (HSP) for the KUKA GSD, or TIA Portal V16+ with the GSD file installed under Options → Manage General Station Description Files (GSD).
• WorkVisual installation matching the KSS version on the KRC4 (the CD bundled with the controller has the correct pairing – do not use a newer or older WorkVisual than the KSS).
• Network connection to the KRC4 service Ethernet port (X66 on KRC4) or to the cell network. The KUKA service interface is typically 192.168.0.1 / 255.255.255.0; the cell PROFINET network must be reachable from the engineering PC.
• Administrator / "Expert" user rights on the KRC4 to deploy the WorkVisual project.

6. Step-by-Step Resolution

1. Export the current KRC4 project to WorkVisual. Connect to the KRC4 with WorkVisual, log in as Expert, and pull the active project via File → Save Project As (from the robot). The project opens with the existing PROFINET configuration visible under the Bus Structure → PROFINET node.
2. Open the PROFINET node properties. In the project tree, right-click the PROFINET subnet the KRC4 is using for its own distributed I/O and select Properties. Under the General tab there is a section PROFINET Stack (in older KSS releases it appears as Interface). Two radio buttons / checkboxes control the role: PROFINET Controller and Activate PROFINET device stack.
3. Tick "Activate PROFINET device stack." This is the action that resolves the error. With this option enabled, the KRC4 builds a second PROFINET interface that presents the configured slots toward the S7-300 as a PN-IO device. The KRC4 retains its controller role for the existing remote I/O on the cell network.
4. Configure the device-side slots. After activating the device stack, a new PROFINET Device element appears under the KRC4. Add input and output modules that match the SIMATIC HW Config. The most common mapping for simple bit-for-bit exchange is 1 byte of inputs + 1 byte of outputs (slot 1 = 1 Byte In, slot 2 = 1 Byte Out). For larger mappings, add multiple byte/word modules up to the KRC4's device-side limit (typically 256 bytes per direction on KSS 8.3).
5. Assign the PROFINET device name. The name entered here (e.g., krc4cell1) must match exactly the device name you enter in STEP 7 / TIA Portal under PROFINET IO → KRC4 → Properties → PROFINET device name. Case-sensitive, no spaces, ≤ 240 characters per PROFINET naming rules.
6. Assign the IP address. The device stack is bound to a KUKA PROFINET port (typically the KRC4's X65 port on the customer-side PROFINET network). Set the IP/subnet consistently with the S7-300 subnet, e.g., 192.168.1.50 / 255.255.255.0.
7. Compile and deploy. Project → Build (F5) until the orange errors disappear, then Online → Deploy to the KRC4. The robot will prompt for a cold restart – accept it. After reboot, the KRC4 holds the new project with the device stack active.
8. Re-assign the name from STEP 7. In SIMATIC Manager, right-click the KRC4 IO device → PROFINET Device Name → Assign Name. Browse to the KRC4 MAC, select it, and assign the exact same name you typed in WorkVisual. This step is mandatory even if you typed the name in WorkVisual; the PLC project must own the DCP name assignment so the AR can be opened by the S7-300.

7. WorkVisual Configuration Deep Dive

The Activate PROFINET device stack option is documented in the KUKA PROFINET integration manual that ships with WorkVisual. The relevant parameters in the WorkVisual bus editor are:

The PROFINET specification from PI (PROFIBUS & PROFINET International) requires that a device that exposes multiple slots must publish a real GSD file. KUKA does this; the GSD is installed with WorkVisual and appears in STEP 7 / TIA Portal as KUKA Roboter GmbH → KRC4 → KR C4 PROFINET Device. Always import the GSD from the WorkVisual install path, not a copy off a colleague's laptop – the GSD is versioned against KSS.

8. SIMATIC Manager HW Config Verification

After the KRC4 has been re-deployed with the device stack, the SIMATIC HW Config must show the KRC4 with green checkmarks in the online view. The verification sequence is:

1. Compile the STEP 7 project (Station → Consistency Check).
2. Download HW Config to the S7-314C-2 PN/DP (target system → PLC → Download).
3. Open Online → Accessible Nodes and confirm the KRC4 appears as a PROFINET IO Device with a green status icon.
4. In the diagnostic buffer, the previous RPC errors should be replaced by an informational entry: PROFINET IO: AR established.
5. Force a bit on the KRC4 side (e.g., from a KRL program with $OUT[1] = TRUE) and monitor it in VAT or in the HW Config IO view on the S7-300 side at input byte 0, bit 0.

9. Verification and Diagnostic Checks

Use the following layered verification to confirm the link is healthy before commissioning motion or safety logic over it:

10. Extended Troubleshooting Matrix

11. Best Practices and Field Notes

• Always enable the device stack even if the S7-300 is the only controller in the cell. It costs nothing at runtime and avoids the "but it was the device stack again" call-out at the next integration.
• Keep the controller-side PROFINET on a separate subnet from the device-side PROFINET when possible. KRC4 supports two PROFINET interfaces in KSS 8.3+; use the second physical port to physically isolate the S7-300 link from the KRC4's own remote I/O.
• Match the device name in three places: the WorkVisual project (offline), the KRC4 runtime (after deploy), and the SIMATIC HW Config. A mismatch in any one of the three will produce AR errors.
• Document the slot map (e.g., slot 1 = byte 0 inputs, slot 2 = byte 0 outputs) in the project header so the KRL programmer and the PLC programmer agree. KRL accesses the device stack via $PROFIO_IN[n] and $PROFIO_OUT[n] indexed per byte/bit.
• Do not name the PROFINET subnet the same on both sides. The PROFINET IO subnet name is purely administrative; only the DCP device name must match.
• For PROFIsafe over PROFINET, an additional PROFIsafe host (e.g., a SINUMERIK or F-CPU) is required. The KRC4 device stack is for non-safe signals only.
• Firmware pairing with STEP 7: STEP 7 V5.5 SPx can program the S7-314C-2 PN/DP down to firmware V3.3.x. If the CPU firmware is older (V2.x), upgrade with a SIMATIC Memory Card per SIMATIC S7-300 CPU 31xC firmware update – entry ID 21402108 before commissioning PROFINET.

12. Frequently Asked Questions