Configuring KUKA KRC4 PROFINET Communication with Siemens

Configuring KUKA KRC4 PROFINET Communication with Siemens S7-1200 in TIA Portal

Establishing PROFINET IO communication between a KUKA KR C4 robot controller and a Siemens SIMATIC S7-1200 PLC via TIA Portal is a routine integration task, but the path from an "unreachable" device error to a green I/O link in the project tree crosses two vendor configuration tools (KUKA.WorkVisual and Siemens TIA Portal) and a hardware-specific GSDML description. This field reference consolidates the configuration sequence, byte-mapping workflow, IP/subnet rules, and the diagnostic checks that resolve the most common "KRC4 controller is unreachable" condition after a TIA Portal hardware download.

1. System Overview and Required Components

The reference configuration described in this article matches the typical shop-floor integration profile: a six-axis KUKA robot (KR 10 R900-2 or equivalent) controlled by a KR C4 cabinet, networked PROFINET IO to a Siemens S7-1200 CPU (firmware V4.x or later), and engineering performed on a PC running both WorkVisual 6.0 and TIA Portal V15.1 or higher.

2. PROFINET Topology and Addressing

The KR C4 acts as a PROFINET IO Device; the S7-1200 CPU acts as the PROFINET IO Controller. The relationship is one controller to N devices, and the controller must be the active station on the network. Both stations share a single IP subnet, and PROFINET device names must be unique on the network.

2.1 IP Address Plan

Use a dedicated subnet for the robot cell that does not collide with the plant WAN. The example below uses the RFC 1918 range 172.32.1.0/24:

2.2 PROFINET Device Name Rules

• Maximum 240 characters; recommended ≤ 32 for readability.
• Allowed characters: lowercase letters a–z, digits 0–9, hyphen -, and dot .. Underscore is not permitted in PROFINET device names per the PROFINET specification.
• No leading or trailing dots, no two consecutive dots.
• The name assigned in TIA Portal must match the PROFINET device name written to the KR C4 (this is done inside WorkVisual, not in TIA Portal).

3. WorkVisual 6.0 Project Setup on the KR C4

WorkVisual is the KUKA engineering environment that holds the project archive (.zip archive with all cell configuration, I/O mapping, safety, and option bit configuration). The PROFINET option must be enabled in the project, and the I/O slots must be configured before the GSDML on the TIA Portal side can be aligned with the controller.

3.1 Activate the PROFINET Option on the KR C4

1. Open the active project in WorkVisual 6.0 (File → Open → Project archive or directly from the connected controller via File → Open → From the controller).
2. In the project tree, expand the KR C4 controller node and open Configuration → Network configuration.
3. Confirm the KUKA PROFINET option is installed. In Help → Information the installed option version appears (e.g., Profinet 5.0.3). The PROFINET version on the KRC4 must be one that the TIA Portal GSDML supports.
4. If PROFINET is missing, install via the KUKA option package on the controller's recovery image (KSS recovery USB) or via the KUKA Customer Support portal. A cold restart is required after option installation.

3.2 Export the GSDML File

WorkVisual stores the GSDML that matches the controller's PROFINET firmware version under a known path inside the project archive:

WorkVisual/DeviceDescriptions/GSDML-Vx.x-KUKA-KR_C4-xxxxxxxx.xml

1. Browse the project folder on the engineering PC after the project has been synchronized from the controller.
2. Copy the .xml GSDML file out of the archive to a working directory (e.g., C:\TIA_GSDML\krc4\).
3. Do not edit the GSDML by hand — it is signed and the signature will be invalidated, causing TIA Portal to reject it during import.

4. Importing the GSDML in TIA Portal

1. Open the TIA Portal project containing the S7-1200 station.
2. From the menu bar, choose Options → Manage general station description files (GSD).
3. In the dialog, set the source path to the directory that contains the exported .xml file (e.g., C:\TIA_GSDML\krc4\).
4. Select the GSDML, click Install, and wait for TIA Portal to confirm successful installation. A successful install populates the GSDML into the Devices & Networks hardware catalog under Other field devices → PROFINET IO → [vendor hierarchy].
5. Close the GSD manager. The KR C4 device is now selectable as a PROFINET IO Device in the hardware catalog.

4.1 Add the KR C4 to the PROFINET Network

1. Open Devices & Networks in the project tree.
2. From the hardware catalog, locate the imported KR C4 device and drag it into the PROFINET subnet of the S7-1200.
3. Right-click the new device node → Properties → PROFINET interface → Ethernet addresses:

4. Drag a PROFINET connection from the S7-1200 PROFINET interface port to the KR C4 PROFINET interface port. TIA Portal will create the IO controller / IO device assignment automatically.
5. Open the device view for the KR C4 and confirm that the I/O slots defined in the GSDML match the slots configured in WorkVisual. Typical KUKA slot layout:

5. Assigning the PROFINET Device Name to the KR C4

The PROFINET device name is the single most common reason for a "device unreachable" condition after a successful TIA Portal download. The PLC only accepts AR (Application Relationship) requests from devices whose PROFINET name matches the one configured for the slot in TIA Portal. The name is assigned on the KUKA side from WorkVisual — not from TIA Portal.

1. In WorkVisual 6.0, expand the KR C4 in the project tree and open Configuration → Network configuration → PROFINET.
2. Edit the PROFINET device name field. Use the lowercase name krc4 (or the value configured in TIA Portal).
3. Edit the IP address to 172.32.1.55 and the subnet mask to 255.255.255.0.
4. Save the project, then deploy to the controller (Deployment → Install or the deploy-to-controller icon in the toolbar).
5. Perform a cold restart of the KR C4 (full power-down, then power-up). PROFINET device-name changes are only committed during a cold restart on the KR C4; a warm restart (software reboot from the smartPAD) will not persist the name change on all KSS versions.

6. TIA Portal Hardware Compile and Download

1. In TIA Portal, right-click the S7-1200 station → Compile → Hardware and software (rebuild all). Resolve any errors before continuing.
2. Connect the engineering PC to the S7-1200 PROFINET port.
3. Right-click the S7-1200 → Download to device → Hardware and software.
4. In the download dialog, set the PG/PC interface to the PROFINET NIC. Use Accessible devices to confirm that the S7-1200 CPU is reachable on 172.32.1.10 before downloading.
5. Perform the download. The CPU will go through STOP → run-up → RUN. The PROFINET IO controller startup begins immediately after CPU enters RUN.

6.1 Online Reachability Verification

1. In TIA Portal, with the S7-1200 online, right-click the PROFINET subnet → Online & diagnostics.
2. Open the Devices in the subnet view. The KR C4 should appear with a green status indicator.
3. Drill into the KR C4 → Status. The station status field shows "Connected" and the AR status should report AR established.
4. If the station is still "Unreachable":

• Confirm PROFINET device name on the KRC4 (smartHMI → Configuration → Network) matches exactly the value in TIA Portal. PROFINET device names are case-sensitive.
• Confirm the IP address on the KRC4 (smartHMI → Configuration → Network) matches TIA Portal.
• Confirm the GSDML version in TIA Portal (Properties of the device → Catalog) matches the KUKA PROFINET option version installed on the cabinet (visible in smartHMI under Help → Information).
• Confirm that the S7-1200 firmware supports the KUKA PROFINET GSDML revision. TIA Portal will warn on incompatible GSD revisions during device insertion; address this before downloading.

7. I/O Byte Mapping Between the KR C4 and the PROFINET Image

Once the PROFINET AR is established, the I/O bytes configured in TIA Portal are mapped to S7-1200 process-image areas. The PLC programmer then maps these to the S7-1200 I/O tags that the application reads and writes.

7.1 Default I/O Image Layout (32 bytes in / 32 bytes out)

7.2 Mapping the PLC Side

1. In TIA Portal, with the KR C4 device view open, click the input slot 0 to highlight its I/O addresses. The default start address is typically I 0 (PLC tag area for PROFINET slot 0 input).
2. Right-click → Properties → Module parameters if you need to change the slot length or rename the channel. KUKA GSDMLs expose the slot as a 32-byte module; the start address can be reassigned in the I/O address overview of the device view.
3. Open a function block in the S7-1200 program and declare a tag table that maps symbolic names to the process-image addresses:

// S7-1200 symbolic tag mapping example (TIA Portal tag table)
// Robot -> PLC (inputs)
"robot_status\         AT %IB0  : BYTE;  // bit 0 = program running, bit 1 = motion complete
"robot_error_code      AT %IB1  : BYTE;
"robot_position_word   AT %IW2  : WORD;  // user-defined position feedback

// PLC -> Robot (outputs)
"plc_cmd_program_sel   AT %QB0  : BYTE;  // program number to start
"plc_cmd_start         AT %Q0.0 : BOOL;  // start selected program (rising edge)
"plc_cmd_stop          AT %Q0.1 : BOOL;  // stop current program
"plc_cmd_ack           AT %Q0.2 : BOOL;  // acknowledge alarms

7.3 Mapping the KRC4 Side in WorkVisual

The same 32 input bytes and 32 output bytes are visible inside WorkVisual as PROFINET signals in the project tree. Each signal has a name and a direction.

1. In WorkVisual 6.0, expand Configuration → I/O mapping → PROFINET (or the equivalent, depending on the option build).
2. For each PROFINET input byte coming from the robot (output to the PLC), define a name. The WorkVisual names appear in the KRL (KUKA Robot Language) program as $IN[1]..$IN[32] or named signals.
3. For each PROFINET output byte (input from the PLC), define a name. The names appear in KRL as $OUT[1]..$OUT[32].
4. Save the project and deploy to the KR C4, then perform a cold restart.

7.4 Cross-Reference Between TIA Portal and WorkVisual

The mapping relationship is symmetric: byte N from the PLC's PROFINET input slot becomes signal $OUT[N+1] in the KRL program, and byte N from the PLC's PROFINET output slot becomes signal $IN[N+1]. The convention is "out of one side, in to the other". Confirm symmetry on a bench before wiring field I/O.

8. Verification Checklist

After the first end-to-end power-up, walk through the following matrix before handing the cell to production:

9. Common Faults and Diagnostic Path

10. Update Time and Real-Time Tuning

The PROFINET update time is the cycle at which the IO controller and device exchange process data. The KRC4 supports a range of update times depending on the PROFINET option build; conservative values are recommended for first commissioning.

Set the update time in TIA Portal under Device view → KR C4 → Properties → PROFINET interface → Real time settings → Update time. Match the send clock of the IO controller (S7-1200 PROFINET port) to a value the KR C4 supports — typically 1 ms for S7-1200 CPUs from firmware V4.2 onward.

11. Edge Cases and Field-Proven Caveats

• KRC5 with PROFINET 6.0.2. The KRC5 cabinet uses a different PROFINET stack and the GSDML is generated by a newer WorkVisual release (typically 6.0.x or later). The setup workflow is identical but the GSDML is incompatible with the KRC4 GSDML; never mix them.
• Multiple robots in one cell. Each KR C4 must have a unique PROFINET device name and IP. Duplicate device names cause AR establishment failure for the second device.
• Safety integration. The PROFINET discussed here is non-safe (PROFINET IO, not PROFIsafe). If the cell uses PROFIsafe, the safety controller and PROFIsafe slot configuration are separate and must be added on top of this configuration.
• Watchdog time. The IO controller's watchdog time (configurable on the slot in TIA Portal) defines how long the controller waits for an IO device response before signaling station failure. For a robot cell with bursty motion, set the watchdog to at least 3× the update time to avoid nuisance failures.
• Re-deploying from WorkVisual clears the device name. Some KSS versions clear the PROFINET device name when a new project is deployed. If the device becomes unreachable immediately after a WorkVisual deploy, re-enter the device name in WorkVisual, redeploy, and cold-restart the KR C4.
• Topology discovery via LLDP. Use TIA Portal Online & Diagnostics → Topology to confirm that the S7-1200 sees the KRC4 as a PROFINET neighbor on the expected port. A missing neighbor indicates a physical-layer issue (cable, switch, port).

12. Putting It All Together: First-Time Integration Flow

1. Connect the engineering PC to X66 on the KR C4 and the PROFINET port of the S7-1200 via a managed switch (or directly with a crossed cable if no switch is used).
2. In WorkVisual 6.0, open the project from the controller, confirm PROFINET option version, and set the IP 172.32.1.55 and PROFINET device name krc4.
3. Deploy the project to the KR C4 and perform a cold restart.
4. Export the GSDML from WorkVisual/DeviceDescriptions/.
5. In TIA Portal, install the GSDML via Options → Manage general station description files (GSD).
6. Add the KR C4 from the hardware catalog to the S7-1200 PROFINET subnet, set IP 172.32.1.55 and device name krc4, and link the PROFINET ports.
7. Compile the S7-1200 hardware configuration and download to the CPU.
8. Map I/O bytes between WorkVisual and TIA Portal using a documented cross-reference.
9. Run the verification checklist in section 8 above before opening the cell to production traffic.

13. Reference to Official Documentation

For deeper information beyond this article, consult the following primary documentation resources:

• KUKA.PROFINET option page (KUKA.com) — option scope, supported firmware versions, cabinet compatibility matrix.
• KUKA.WorkVisual documentation portal (KUKA.com) — operator manual, project lifecycle, deployment procedures.
• Siemens Industry Online Support (support.industry.siemens.com) — TIA Portal manuals, S7-1200 system manual, GSDML import procedure, PROFINET diagnostics.
• PROFINET specification and user organization (profinet.com) — device-naming rules, AR establishment, conformance classes.
• S7-1200 and KUKA KR C4 — SiePortal thread (siemens.com) — community-shared integration report with the same controller/PLC pair.

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