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Replacing CPU 410-5H Across Plant Bus and CP 443-1 Communication Processors in PCS 7 V8.1

Replacing CPU 410-5H Across Plant Bus and CP 443-1 Communication Processors in PCS 7 V8.1

Replacing a SIMATIC PCS 7 CPU 410-5H controller in legacy installations operating with an external CP 443-1 communication processor requires specific initial commissioning steps. Because brand-new CPU 410-5H units have no pre-assigned IP address or hardware parameters, the Engineering Station cannot communicate via standard S7 connections until the controller is initialized. Engineers must assign a temporary IP via Edit Ethernet Node using the CPU MAC address, uncheck 'Store configuration data on CPU' on legacy CP modules if routing conflicts occur, accommodate extended unbuffered startup delays, and download the hardware configuration.

Table of Contents

Controller Replacement Challenges in Legacy Architectures

When upgrading or replacing an older controller with a modern CPU 410-5H in SIMATIC PCS 7 V8.1, engineering workflows differ significantly from older S7-400 CPUs (such as CPU 416-3 DP):

  • No Dedicated MPI/DP Engineering Cable Required: While legacy S7-400 CPUs were typically commissioned on-site by connecting a Field PG via an MPI/DP cable, the CPU 410-5H is commissioned directly across Industrial Ethernet using Layer 2 MAC broadcasting.
  • The Uninitialized Controller State: A factory-fresh CPU 410-5H unboxed from Siemens has zero IP configuration, empty memory, and no S7 connection tables. It cannot be reached via standard TCP/IP routing from the Engineering Station (ES) until Layer 2 initialization occurs.
  • Legacy CP 443-1 Interaction: In older systems migrated to CPU 410 hardware, an external communication processor (CP 443-1) often remains in the rack to handle legacy plant bus subnets. If the CP is configured to store configuration data on the CPU, an empty replacement CPU prevents the CP from establishing its network interface, blocking remote access.

Initial IP Assignment via MAC Address and Edit Ethernet Node

Before the ES can download HW Config or CFC programs across the plant bus, assign the controller its permanent IP identity:

  1. Locate the physical MAC Address printed on the front label of the replacement CPU 410-5H (e.g., 00-1B-1B-XX-XX-XX).
  2. Connect the ES to the Plant Bus switch connected directly to the CPU's onboard PROFINET port (PN-IO X1).
  3. In SIMATIC Manager, select PLC -> Edit Ethernet Node....
  4. In the dialog, click Browse... to scan the local Layer 2 broadcast domain.
  5. In the accessible nodes list, locate the entry matching the CPU's printed MAC address.
  6. Select the device and click OK.
  7. In the "Assign IP Configuration" section:
    * Enter the exact IP address and Subnet mask configured for the CPU in the project HW Config.
    * Enter the Gateway IP if routing across subnets.
  8. Click Assign IP Configuration.
  9. The CPU operating system immediately applies the IP address without requiring a power cycle.

Handling Legacy CP 443-1 Configuration Data Storage

In installations where plant bus communication passes through a rack-mounted CP 443-1 rather than the onboard CPU ports:

  • The Configuration Storage Flag: In HW Config under CP 443-1 Properties, the option Save configuration data on the CPU dictates whether the CP fetches its IP and routing tables from the CPU backplane upon power-up.
  • The Replacement Trap: When a brand-new, unprogrammed CPU is inserted, the CPU backplane contains no configuration data for the CP. Consequently, the CP 443-1 boots with default parameters and fails to bring up its plant bus IP, preventing the ES from reaching the rack.
  • The Solution: Temporarily connect the engineering cable directly to the CPU's onboard PN port to download the hardware configuration, or temporarily uncheck "Save configuration data on the CPU" during commissioning so the CP retains standalone access.

Unbuffered Power-On Startup Delay Characteristics

Engineers familiar with legacy battery-buffered S7-400 controllers are often surprised by the boot behavior of the CPU 410-5H:

  • MRAM Non-Volatile Architecture: The CPU 410-5H does not use backup lithium batteries; it utilizes internal non-volatile ferroelectric RAM (MRAM) and a System Expansion Card (SEC).
  • Extended Boot Duration: After an unbuffered "Power ON" (Netz EIN), the CPU 410-5H executes extensive internal memory integrity checks, self-diagnostics, and SEC cryptographic authentication.
  • Startup Timing: This initialization sequence can require 2 to 5 minutes before the CPU communication interfaces become active and the STOP or RUN LEDs stabilize. Commissioning engineers must avoid power-cycling the rack prematurely while the CPU executes initial boot routines.

Step-by-Step Replacement and Hardware Download Procedure

Follow this structured procedure when replacing a CPU 410-5H:

  1. Hardware Preparation:
    * Power down the rack.
    * Transfer the existing System Expansion Card (SEC) from the old CPU to the replacement CPU 410-5H.
    * Seat the new CPU into the rack, reconnect network cables, and power on.
    * Wait 3 to 5 minutes until the CPU finishes boot diagnostics.
  2. Assign Temporary IP Address:
    * Open SIMATIC Manager -> PLC -> Edit Ethernet Node.
    * Browse by MAC address and assign the project IP address.
  3. Download Hardware Configuration:
    * Open HW Config for the automation station.
    * Select PLC -> Download.
    * Select the CPU target address and execute the download.
  4. Download Complete Program:
    * Select the Charts folder in SIMATIC Manager.
    * Execute PLC -> Download (Scope: Entire program).
    * Switch the CPU mode switch from STOP to RUN.

Verification

Confirm successful controller replacement and operational readiness:

  1. Module Information Audit:
    * Select the CPU in SIMATIC Manager and press Ctrl + D.
    * Confirm that the firmware version, serial number, and hardware release are recognized.
    * Verify that the Process Objects tab confirms the full PO capacity from the transferred SEC.
  2. Communication Link Verification:
    * Open NetPro. Verify that active S7 connections to WinCC OS servers and peer controllers report green operational status.
  3. Cyclic Logic Execution:
    * Open an active CFC chart in Test Mode; verify that dynamic monitoring functions normally and that distributed I/O racks report zero bus faults.

Limitations and Operational Precautions

  • Firmware Parity: Ensure the replacement CPU 410-5H firmware is equal to or higher than the predecessor; PCS 7 V8.1 typically requires CPU 410 firmware V8.1.x or approved spare-part compatibility configurations.
  • SEC Transfer Mandate: Never power up a replacement CPU without the original SEC card installed; the controller cannot run without a valid System Expansion Card.
  • Non-Redundant Plant Interruption: In a single-station (non-redundant) architecture, replacing a CPU requires a complete plant stoppage for the duration of the replacement.

Engineer FAQ

  • How do I connect to a brand-new CPU 410-5H that has no IP address assigned?
    Use 'PLC -> Edit Ethernet Node' in SIMATIC Manager to scan for the CPU's physical MAC address over Layer 2 Ethernet and assign the project IP.
  • Why does the CPU 410-5H take several minutes to start up after power is turned on?
    The CPU 410-5H executes extensive MRAM integrity checks, cryptographic SEC validation, and internal self-diagnostics upon unbuffered power-on.
  • Can I use an MPI cable to commission a CPU 410-5H?
    The CPU 410-5H does not have an MPI port; commissioning is performed exclusively over Industrial Ethernet using the onboard PN ports.
  • What causes a legacy CP 443-1 to lose its IP when the CPU is replaced?
    If the CP is configured to 'Save configuration data on the CPU', an empty replacement CPU supplies no configuration, causing the CP to boot unconfigured.
  • Where is the MAC address located on the CPU 410-5H?
    The factory MAC address is laser-printed on the front housing of the CPU below the lower door, and on the module barcode label.
  • Can I replace a CPU 410-5H remotely over routers?
    Initial Layer 2 MAC address assignment requires the Engineering Station to reside on the same physical broadcast domain (VLAN) as the CPU.
  • Does replacing the CPU require purchasing new AS Process Object licenses?
    No, transferring the original System Expansion Card (SEC) preserves the controller's hardware PO entitlement, and existing software POs can be downloaded from the ES.
  • What should I do if the replacement CPU has newer firmware than configured in PCS 7 V8.1?
    Modern CPU 410 units support backward-compatible drop-in spare-part replacement; you can download the existing HW Config without updating the catalog version.
  • What is the function of the MRES switch position on the CPU 410-5H?
    Holding the mode switch in MRES triggers an overall reset, clearing work memory while retaining firmware and the SEC hardware capacity.
  • How do I verify that the CP 443-1 has resumed communication?
    Check the CP 443-1 front LEDs: RUN must be steady green and STOP must be off; verify accessibility in STEP 7 Accessible Nodes.

Technical References

  • Siemens Industry Online Support (SIOS) Portal: Process Automation with SIMATIC PCS 7 CPU 410-5H Manual (Entry ID: 96839331).
  • SIMATIC S7-400 / CPU 410-5H Commissioning and Service Guidelines, Siemens AG.
  • SIMATIC NET CP 443-1 Operating Instructions, Siemens AG.

Related Articles

Related Tags

PCS 7, CPU 410, CPU 410-5H, CP 443-1, Hardware Replacement, Edit Ethernet Node, MAC Address, Commissioning

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