PROFINET Device Replacement Without Exchangeable Medium in TIA Portal

The PROFINET option Support device replacement without exchangeable medium is a TIA Portal hardware configuration setting that lets a SIMATIC controller (S7-1200, S7-1500, ET 200SP CPU, ET 200MP CPU) push the Name of Station and the IP Suite to a replacement IO device using only the configured PROFINET topology, with no SD card, SIMATIC Memory Card, or engineering station required on the shop floor. This article is the engineer field guide: it explains exactly what the option does, which devices support it, how to wire the topology, how to commission it, and how to recover when it does not behave as expected.

1. What the Option Actually Does

When you enable the checkbox in the PROFINET interface of a PROFINET IO device, you instruct the IO controller to behave as if a memory card holding the station name and IP parameters were already inserted. Mechanically, this is a PROFINET DCP (Discovery and Configuration Protocol) name-and-IP assignment triggered by the controller instead of by an external PG, the PRONETA tool, or the device's removable medium.

PROFINET uses LLDP (IEEE 802.1AB) for neighbor detection and topology discovery. The IO controller learns which physical port a device is connected to by reading the LLDP TLVs. Because the engineering project also contains the planned port-to-port topology, the controller can correlate the live LLDP neighbor with the configured device at that exact port and push the right station name and IP to it. See the official Siemens function manual PROFINET with STEP 7 - ID: 49948856 for the full protocol behavior.

2. When to Enable the Option

Enable it in three situations:

1. The IO device has no serviceable slot for an exchangeable medium — for example the ET 200SP (without the optional SD card slot populated) and most ET 200MP head modules. The official Siemens definition reference lists ET 200SP and ET 200MP explicitly.
2. Hot-spare cabinets where you want to swap a head module in less than 60 seconds and cannot attach a PG to the machine.
3. Distributed field cabinets with no laptop, no display, and no service door — the spare module is plugged in and the line restarts automatically.

Disable it when the device is configured permanently, when the topology is not fully known (mobile panels, freely re-arranged stations), or when a removable medium is already provisioned as the primary assignment path.

3. Prerequisites

Before the option does anything useful, all of the following must be true.

4. Underlying Mechanism: LLDP + DCP

The replacement sequence is a three-step handshake inside the controller's PROFINET stack:

1. Discovery — The controller sends LLDP frames out of every port and reads the neighbor TLVs. Each frame carries the controller's own chassis ID and port number.
2. Correlation — The controller matches each LLDP neighbor against the configured topology. The match is performed on (chassis ID + port number) and produces a single candidate IO device per physical port.
3. Assignment — The controller issues a DCP Identify request on that port. A replacement device has no name yet, so it answers with a null Name of Station. The controller replies with DCP Set (Name of Station + IP Suite). The new device reboots its PROFINET stack and comes up as the configured node.

The whole handshake is normally finished inside 5–20 seconds. If the configured topology disagrees with the physical wiring, step two fails and the controller flags a topology error in the diagnostics buffer, so always wire the topology editor before you trust the feature in production.

5. Step-by-Step Configuration in TIA Portal

5.1 Open the Device View

1. In the project tree, double-click Devices & networks.
2. Click the IO device you want to enable (for example IM 155-6 PN HF).
3. Select the PROFINET port of the module in the device view.
4. Open the Properties inspector pane on the right.

5.2 Enable the Option

1. In the Properties pane, switch to the PROFINET interface > Advanced options > Interface options page.
2. Check Support device replacement without exchangeable medium.
3. Repeat for every PROFINET node that may need to be swapped without a memory card.

This is the exact path described in the Siemens knowledge base article How do you replace an IO device without exchangeable medium (109744412).

5.3 Set the Station Name and IP in the Project

1. Open PROFINET interface > Ethernet addresses.
2. Set IP protocol to a fixed address (recommended) or DHCP; avoid the default empty value.
3. Set the PROFINET device name in the form pn-io-device-1 (lower case, dashes only, no spaces).
4. Make sure the subnet is created and the device is assigned to the same subnet as the controller.

5.4 Wire the Topology Editor

1. Switch to the Topology view tab.
2. For every device, drag from one port to the partner port of the next device until every port is connected.
3. Compensate for unmanaged switches: create a Switch object in the topology and connect the two neighbors to ports on it.
4. Save and compile the project. The compile log must show no topology errors.

5.5 Compile and Download

1. Right-click the controller > Compile > Hardware (rebuild all).
2. Download the hardware configuration to the controller (PG/PC cable or routed download via the network).
3. Click Go online and confirm the configuration is identical offline/online.

6. Topology Editor Cheat Sheet

Most failures in the field are topology mismatches, not protocol failures. Use the following reference table when validating the wiring.

7. PLC Program Considerations

The feature is invisible to the cyclic user program. From the S7-1500 CPU point of view, the IO device transitions through the same states it would for any other PROFINET device:

1. Not available — the new head module is powered but has no name yet.
2. Connecting — DCP name write is in progress.
3. Connected (no data) — AR is being established.
4. Data exchange — process data is valid and OB 1 / OB 83 (Device pull/plug) has fired.

You typically handle OB 83 in the user program to reset latched I/O or to retrigger startup logic. A minimal example for STEP 7 in Structured Text on an S7-1500:

// OB 83 - Pull/Plug interrupt for PROFINET IO device replacement
IF #EventClass = OB83 AND #Fault_ID = DW#16#0000_0000 THEN
    // Replacement: clear process image of the new device
    // and re-initialize the field-side outputs.
    "init_outputs"(io_index := #LADDR_idx);
END_IF;

If you use PROFIenergy or shared device on the same head module, the station name and IP must match slot 0, regardless of which slot the head module is configured for. Double-check the Interface options page to make sure the head module is not configured to read its name from a non-existent MMC slot.

8. Device Replacement Workflow on the Shop Floor

Once the project is in production, the operator-side procedure collapses to a tight checklist.

1. De-energize the field cabinet and lock out.
2. Pull the defective head module.
3. Insert the spare module. The spare must be the same order number, the same firmware major version, and the same I/O configuration (a pre-loaded variant is recommended).
4. Apply power to the head module. Wait for LLDP discovery (1–2 s).
5. The controller issues DCP Set (Name of Station + IP Suite) over the configured port. This is observed in the controller's online diagnostics as a sequence of Station OK events.
6. The spare module reboots its PROFINET stack and re-enters data exchange. OB 83 fires on the CPU.
7. Verify the IO LEDs on the spare head module are solid green. Verify in TIA Portal with Online & diagnostics > PROFINET topology that the spare is reporting the correct neighbors on the correct ports.

9. Verification

After downloading the new configuration, validate the feature end to end.

Document the verification evidence as a screenshot of the accessible devices list and the topology view. These are the artifacts that a FAT/SAT auditor will want to see for any safety-relevant swap path.

10. Frequently Seen Diagnostic Events

The controller exposes a small set of events in the diagnostic buffer when the option is enabled. Knowing them saves a service call.

11. Field-Commissioning Checklist

Use this list when commissioning a new line or retrofitting an existing cabinet.

1. Verify each PROFINET head module is on the firmware version listed in the device manual's Device replacement without exchangeable medium chapter. For ET 200SP IM 155-6 PN HF this is FW 3.0 or higher; for ET 200MP IM 155-5 PN HF this is FW 3.1 or higher. Update the spare units first so the swap does not cascade a firmware mismatch.
2. Build the topology in the office, not on the shop floor. Use the schematic to assign port-to-port relationships and bring the topology to site already pre-wired in the project.
3. Decide on the IP allocation scheme in advance. A fixed IP per device avoids surprises when a spare is reused across different lines.
4. Enable the option on the device properties (not on the controller properties) for every replacement candidate.
5. Do a controlled test swap at the end of commissioning and write the result into the SAT report.
6. Train the maintenance crew on the swap procedure and on what to do if the IO LEDs do not turn green within 60 seconds — they should default to a controlled PG assignment and call automation engineering, not a re-power loop.

12. Related Standards and References

The feature is built on top of the PROFINET specification maintained by PROFIBUS International (PI). The relevant concepts are documented in the following PI documents, which the official Siemens function manual PROFINET with STEP 7 - ID: 49948856 maps to the TIA Portal user interface:

• PROFINET Installation Guideline (PROFIBUS International)
• PROFINET Commissioning Guideline (PROFIBUS International)
• PROFINET Security Guideline (PROFIBUS International)

Use these guidelines to verify that the device replacement workflow also satisfies plant cybersecurity rules. In some regulated environments, DCP-based name assignment must be allowed explicitly in the firewall rules of the cell.

13. Frequently Asked Questions