C135 PCS 7 (PCS7)
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Assigning IP Addresses and Commissioning SIMIT Units via SIMIT Unit Administration

Assigning IP Addresses and Commissioning SIMIT Units via SIMIT Unit Administration

To discover a physical SIMIT Unit (such as SIMIT Unit PN 128 / PB 128 / Unit 256) and assign an IP address via SIMIT Unit Administration when connected via RJ-45 to the CTRL port: 1) In Windows, configure your PC network adapter with a fixed static IP address (e.g., 192.168.1.50 / 255.255.255.0); 2) In SIMIT Unit Administration, open the Network Settings and bind the tool explicitly to that physical network adapter; 3) Disable Windows Defender Firewall or permit Layer-2 DCP broadcast protocols; 4) Under 'SU hardware/firmware', execute a scan to detect the unconfigured SIMIT Unit MAC address; and 5) Assign the target IP address and subnet mask to the CTRL interface, then save the configuration.

Table of Contents

Executive Summary

Hardware-in-the-Loop (HIL) simulation provides deterministic, real-time emulation of distributed I/O devices on PROFINET IO and PROFIBUS-DP networks using dedicated Siemens SIMIT Units. When unboxing and commissioning a new SIMIT Unit, automation engineers connect an Ethernet cable between their simulation PC and the management port (CTRL), only to find that SIMIT Unit Administration fails to discover the appliance under 'SU hardware/firmware', reporting zero accessible nodes. This issue arises from unconfigured Layer-2 Discovery and Configuration Protocol (DCP) bindings and Windows network interface selection. This technical guide explains the dual-port architecture of SIMIT Units, details DCP discovery requirements, and provides the step-by-step IP assignment workflow.

Architecture and Fundamental Mechanics

SIMIT Unit Physical Interface Architecture and DCP Discovery

+-------------------------------------------------------------------------+
|                        SIMIT Simulation PC                              |
|   - Physical NIC (Static IP: 192.168.1.50)                              |
|   - SIMIT Unit Administration Tool (DCP Discovery Engine)               |
+-----------------------------------|-------------------------------------+
                                    |
                                    v Standard RJ-45 Ethernet Cable
+-----------------------------------|-------------------------------------+
|               SIMIT Unit Appliance (PN 128 / PB 128)                    |
|                                                                         |
|   [CTRL Port] (Ethernet Management Port)                                |
|   - Factory Default: No IP Address (DCP Broadcast Listening)            |
|   - MAC Address printed on hardware nameplate                           |
|                                                                         |
|   [BUS Ports] (Fieldbus Simulation Ports)                               |
|   - Connects to S7-400H / CPU 410-5H PROFINET or PROFIBUS Lines         |
|   - Emulates up to 128 or 256 field devices in real-time                |
+-------------------------------------------------------------------------+

The Discovery Failure Mechanism

  1. Unassigned Out-of-the-Box State: Brand new SIMIT Units leave the factory with zero assigned IP addresses. They do not run a DHCP server and will not respond to ICMP ping.
  2. Layer-2 DCP Protocol: Like SIMATIC S7 controllers and ET 200 interface modules, SIMIT Unit discovery relies on PROFINET Discovery and basic Configuration Protocol (DCP), which operates at the Ethernet Data Link Layer (MAC broadcast) rather than IP routing.
  3. Network Adapter Binding: If SIMIT Unit Administration is defaulted to a virtual adapter, corporate Wi-Fi card, or VMware bridge, DCP broadcast frames are sent out the wrong physical interface, failing to reach the CTRL port.
  4. Firewall Blocking: Modern Windows operating systems classify unconfigured direct-cable connections as 'Unidentified Public Networks', applying aggressive firewall rules that drop incoming Layer-2 DCP response packets.

Step-by-Step Implementation Procedure

Step 3: Configure Network Adapter in SIMIT Unit Administration

  1. Open SIMIT Unit Administration (from Windows Start or within SIMIT Simulation Platform).
  2. In the top menu bar, select Options > Settings (or Adapter Selection).
  3. In the Network Adapter dropdown, explicitly select the physical network card configured in Step 2 (e.g., Intel Ethernet Connection I219-LM).
  4. Click OK to bind the discovery socket to that adapter.

Step 4: Scan and Assign IP Address via 'SU Hardware/Firmware'

  1. In SIMIT Unit Administration, navigate to the tab SU hardware/firmware.
  2. Click the button Find Accessible Devices (or Search / Refresh).
  3. The tool will broadcast DCP frames. Within 5 to 10 seconds, the SIMIT Unit will appear in the table, identified by its factory MAC address (e.g., 00:1B:1B:...) and device type (SIMIT Unit PN 128).
  4. Select the detected unit in the list.
  5. Enter the desired network parameters for the CTRL interface:
    - IP Address: 192.168.1.100
    - Subnet Mask: 255.255.255.0
    - Device Name: simit-unit-01
  6. Click Assign IP Configuration (or Apply).
  7. Confirm that the status message indicates successful IP assignment.

Step 5: Verify SIMIT Project Coupling

  1. Launch SIMIT Simulation Platform.
  2. Open your simulation project.
  3. In the project tree under Couplings, create a new coupling of type SIMIT Unit.
  4. In the coupling properties, enter the assigned IP address (192.168.1.100).
  5. Import the HW Config export file (*.cfg) from Step 7 to map controller I/O into the SIMIT Unit.

Verification

  1. Ping Verification: In Windows Command Prompt, execute: ping 192.168.1.100. Confirm steady ICMP replies with latency <1 ms.
  2. Firmware and Health Query: In SIMIT Unit Administration, click Query Device Information. Confirm that firmware version, operating status, and MAC addresses are populated accurately.
  3. Active Coupling Test: In SIMIT Simulation Platform, start the simulation. Verify that the SIMIT Unit coupling indicator turns green, confirming active communication.

Limitations and Operational Precautions

  1. Distinct Subnets for CTRL and BUS: Never assign the CTRL port and the simulation BUS ports to the same IP subnet; the internal routing architecture of the SIMIT Unit requires distinct subnets to prevent network packet loops.
  2. License Assignment: Ensure your SIMIT license in ALM includes the SIMIT Unit coupling feature; without it, SIMIT cannot initialize hardware-in-the-loop couplings.

Engineer FAQ

Which physical port is used to configure a SIMIT Unit?

The CTRL (Control) Ethernet port is used exclusively for configuration and simulation PC communication.

Why does SIMIT Unit Administration fail to find the device?

The tool is bound to the wrong network adapter, Windows Firewall blocked Layer-2 DCP discovery, or the PC lacks a static IP.

Does a new SIMIT Unit have a default IP address?

No, out of the box it has only a MAC address and must be assigned an IP using PROFINET DCP protocol.

What is the difference between SIMIT Unit PN 128 and PN 256?

PN 128 simulates up to 128 PROFINET field devices; PN 256 simulates up to 256 field devices in real-time.

Can I assign an IP address using Proneta or Step 7 Edit Ethernet Node?

Yes, because the SIMIT Unit supports standard PROFINET DCP, standard Siemens discovery tools can also assign its IP.

Can the CTRL port and BUS ports be on the same IP subnet?

No, they must be on different subnets to avoid network routing conflicts inside the appliance.

Does SIMIT Unit replace S7-PLCSIM?

S7-PLCSIM emulates the CPU controller; SIMIT Unit emulates physical fieldbus I/O modules connected to a real physical controller.

What cable is required between PC and SIMIT Unit?

A standard RJ-45 Cat5e or Cat6 patch cable (auto-MDIX handles crossover automatically).

Where can I update SIMIT Unit firmware?

Firmware updates are uploaded directly through SIMIT Unit Administration under the SU Hardware/Firmware tab.

Where can SIMIT Unit hardware be purchased?

Through an authorized Siemens distributor or the Siemens Industry Mall.

Technical References

Related Articles

Related Tags

  • SIMIT Unit
  • HIL Simulation
  • CTRL Port
  • DCP Discovery
  • SIMIT Unit Administration
  • PROFINET
  • SIMIT V10.2
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