WinCC 7.0 SP1 Redundant Communication with S7-400H via CP 1613

1. System Overview and Target Architecture

The reference architecture described here is a Siemens SIMATIC S7-400H (H = High Availability / fault-tolerant) system talking to two redundant WinCC 7.0 SP1 server stations over Industrial Ethernet. Each server PC is fitted with two SIMATIC NET CP 1613 (6GK1161-3AA01) communications processors, one bound to the primary S7-400H CPU and one bound to the standby CPU. The redundant server pair then serves WinCC clients and provides a hot-standby HMI/SCADA layer above the redundant PLC.

Three things distinguish an S7-400H link from a standard S7-400 link and make this configuration non-trivial:

1. The H-CPU pair (e.g., CPU 412-3H, 414-4H, 417-4H) exposes a single logical connection endpoint to the HMI layer even though two physical CPUs and two PROFINET/Industrial Ethernet CP 443-1 modules are present.
2. WinCC cannot use a plain S7 connection to that endpoint. It must use an S7 Fault Tolerant Connection, which is a NetPro connection object that multiplexes across the two redundant CP 443-1 modules.
3. The PC station side of that Fault Tolerant Connection requires the ISO transport protocol bound to a SIMATIC NET CP 1613 (or compatible) MAC address. Plain S7COMM over TCP (RFC 1006) is not supported for S7 fault-tolerant connections, regardless of CP type.

2. Prerequisites and Component Matrix

The following table lists every component, version, and license required for the path described in this article. Versions are pinned to the WinCC 7.0 SP1 / STEP 7 V5.4 SPx era because that is the version set explicitly stated in the source.

3. CP 1613 Hardware Setup and ISO Protocol Bindings

The CP 1613 is a dedicated communications processor, not a generic NIC. It must be initialised once with the SIMATIC NET "Commissioning" tool so that the MAC address is written to the module and the ISO stack is bound. The relevant steps are:

1. Power down the PC and seat both CP 1613 modules in free PCI slots. Note the slot number (read by the BIOS, used later in the Station Configurator).
2. Boot into Vista SP1, install SIMATIC NET V7.0 + SP7. Reboot. The modules appear in Device Manager → Network Adapters → SIMATIC NET CP 1613.
3. Open Start → SIMATIC → SIMATIC NET → Commissioning → Commissioning Wizard.
4. Select "Configure CP 1613" and assign a unique MAC prefix per card. The default MAC is read from the module's EEPROM and should not be changed unless you have a documented address plan.
5. Set the protocol binding to ISO only. Uncheck "TCP/IP" because the Fault Tolerant Connection object in NetPro requires an ISO endpoint. Mixing ISO and TCP on the same CP produces the error: The default network communication parameters are not compatible for operation in the WinCC communication mode.
6. For each CP 1613 enter the configured MAC address on a printed label and affix it to the bracket — you will need both MACs verbatim when defining the WinCC "Logical Connection Names" later.

4. SIMATIC NET PC Station Configuration

The "PC Station" is the SIMATIC NET runtime representation of the engineering station or server. It must exist on the same STEP 7 project as the S7-400H so that NetPro can wire logical connections across it.

1. In SIMATIC Manager open (or create) the STEP 7 project that contains the S7-400H station.
2. Insert → Station → SIMATIC PC Station. Rename it to match the OS hostname of the server (e.g., WCCSVR01). Repeat for the second server (WCCSVR02).
3. Open HW Config of the PC station. From the catalog insert an IE General under "CP Industrial Ethernet" — but use the CP 1613 entry, not the IE General. Add two of them (CP 1613 #1 and CP 1613 #2), each occupying a slot that matches the physical PCI position.
4. Double-click each CP 1613 → Properties → MAC Address: enter the MAC burned into that physical card. The MAC must match exactly what the Commissioning Wizard reported.
5. Save and compile HW Config. NetPro will now show two Ethernet nodes attached to the PC station.
6. Compile the OS (right-click PC Station → Compile OS) and note the generated XDB file path, e.g., WCCSVR01\S7ONLINE\XDBs\WCCSVR01.xdb. This file is what the Station Configuration Editor on the runtime PC will load.

On the runtime PC:

1. Open the Station Configuration Editor (Start → SIMATIC → Station Configuration Editor).
2. The third component slot must show WinCC Application (Index 3). The CP 1613 modules occupy component slots 1 and 2.
3. Right-click slot 3 → Add… → select "WinCC Application".
4. Right-click the PC station entry → Import Station… → browse to the XDB file produced in step 6 above.
5. The component icon should turn green. A red triangle or yellow exclamation on the CP 1613 slot indicates that the loaded XDB does not match the physical CP at that PCI slot — re-check slot numbering and MAC.

5. STEP 7 / NetPro: Defining the S7 Fault Tolerant Connection

This is the heart of the configuration. The Fault Tolerant Connection object lives only in NetPro and only on the S7-400H side.

1. In NetPro, select the S7-400H station. Open its connections table (right-click CPU → Object Properties → Connections).
2. Insert a new connection. In the connection dialog choose partner = "Unspecified" → Connection Type = "S7 Fault Tolerant Connection". (The plain "S7 Connection" entry is wrong — it will not survive a CPU failover.)
3. In the "Partner" tab, choose "Insert new partner → PC Station" and select WCCSVR01.
4. Set the Local Interface to the CP 443-1 module of CPU 0. The H system will automatically route the connection to CP 443-1 of CPU 1 when CPU 0 fails.
5. Set the Partner Interface to "CP 1613 #1" of the PC station.
6. Confirm the connection. A second partner entry (S7RECONV) is generated automatically — that is normal; do not delete it.
7. Save, compile NetPro, and download the connection configuration to the S7-400H.

For the second server, repeat steps 2–6 against WCCSVR02 with the partner interface set to its "CP 1613 #1". Optionally use a second ISO interface per server (CP 1613 #2) for the standby path; the failover logic is then local to the PC station and the WinCC layer only sees one logical connection.

6. WinCC Tag Management — Loading the XDB and Building the Connection

Once the XDB is loaded into the Station Configuration Editor, the WinCC Explorer on the runtime PC will pick up the named connections automatically:

1. Open WinCC Explorer on WCCSVR01. Right-click Tag Management → SIMATIC S7 PROTOCOL SUITE.
2. Select System Parameters → Logical Device Names. Two logical devices should appear: CP1613_1 and CP1613_2. Map each logical device to the matching physical CP 1613 slot using the dropdown — the entry names must match those from the XDB exactly.
3. Add a new connection of type "Named Connection". Enter the connection name that was defined in NetPro on the S7-400H side (e.g., CONN_HMI_01).
4. Assign CP 1613 #1 as the preferred path, CP 1613 #2 as the fallback. WinCC will switch automatically when the primary connection reports "disconnected" for the configured timeout.
5. Compile the OS once more from STEP 7 to regenerate the XDB and propagate any name changes; re-import on both servers.

7. WinCC Server Redundancy Configuration

WinCC Redundancy is configured separately from the S7 connection redundancy. The two servers must discover each other and replicate the process image, alarm log, and tag logging.

1. In WinCC Explorer on both servers, open Server → Redundancy.
2. Set Redundant Partner Server to the name of the other server (e.g., WCCSVR02).
3. Enable "Partner monitoring via TCP/IP" and enter the partner's WinCC TCP port (default 5678 for the redundancy channel). This is independent of the ISO PLC channel.
4. Set the failover heartbeat to the vendor-recommended default of 5 s; do not raise it above 10 s without verifying with the S7-400H failover budget (typically ≤ 100 ms, so 5 s is conservative).
5. For tag logging, archive redundancy is enabled under Tag Logging → Archive Configuration → Redundancy. Choose "synchronous" for process-critical archives, "asynchronous" for long-term history.
6. For alarms, enable Alarm Logging → Acknowledgement → Sync with Partner to avoid duplicate ACK routing on the operator station.

The result is two distinct failover domains stacked on top of each other:

8. Commissioning and Verification Procedure

Commission in the order PLC → PC station → WinCC project → redundancy tests. Do not skip steps.

1. Verify the S7-400H itself: in STEP 7, online → "Monitor/Modify", force CPU 1 to STOP, confirm CPU 0 takes the master role without error OB 70 calls.
2. On each PC station, open the Station Configuration Editor. All three component slots must show green. The diagnostic log should contain no "Fault" entries.
3. Run the SIMATIC NET "Connection Diagnostics" tool. Each S7 Fault Tolerant Connection should report "established". If a connection shows "not reachable", verify the ISO MAC binding — this is the most common field fault.
4. Start WinCC Runtime on server 1. Confirm tags update by toggling a known bit in the PLC and watching the value change in WinCC Tag Diagnostics.
5. Start WinCC Runtime on server 2. Confirm it reaches WCCSVR01 via the redundancy TCP channel and stays in standby state.
6. Pull the primary Ethernet cable from CP 443-1 (CPU 0). Verify: (a) CPU 1 becomes master within ≤ 100 ms; (b) WinCC remains connected via the fault-tolerant path; (c) tags continue to update.
7. Stop the WinCC service on server 1. Verify: server 2 takes over, clients reconnect within the configured time, archives continue without gaps.
8. Re-start server 1. Verify: it returns to standby, archive catch-up completes (timestamps continuous), no duplicate alarm ACKs.

9. Troubleshooting Matrix

10. Field-Proven Cautions

• ISO endpoint stability: Do not bind ISO and TCP on the same CP 1613. The CP can technically multiplex, but the fault-tolerant extension expects a stable ISO endpoint and will flap if TCP sharing interrupts its timers.
• MAC documentation: Each CP 1613 leaves the factory with a unique MAC burned into EEPROM. Document these on the bracket label before installation. Lost MACs cost hours in field troubleshooting.
• Vista SP1 specific: Microsoft UAC interferes with the Station Configuration Editor if it is started without "Run as administrator". Bake this into the startup shortcut before commissioning.
• License recall: The CP 1613 driver license is counted per CP per server. Two servers × two CP 1613 = four CP 1613 licenses plus one S7-REDCONNECT Powerpack per server.
• Firmware consistency: Mixing firmware levels between the two H-CPUs is permitted but STEP 7 will warn. Standardise on the highest common level before commissioning to avoid asymmetric failover behaviour.
• Test under load: Always commission with the full expected tag and alarm load. A clean install with ten tags will pass tests that fail with ten thousand tags because of the per-cycle CPU cost of the S7 fault-tolerant keep-alive.

11. Standards and Document Cross-References

The configuration above is governed by several Siemens and IEC documents. Verify the latest revision before commissioning:

• SIMATIC NET S7-REDCONNECT Programming Manual — describes the S7 Fault Tolerant Connection object and its ISO dependency.
• SIMATIC S7-400H Fault-Tolerant Systems Manual — defines CP 443-1 failover timing.
• WinCC V7.0 Information System — "Redundancy" chapter.
• STEP 7 V5.5 Online Help, NetPro — connection catalog reference.
• IEC 61784-2 (PROFINET) — for the general fieldbus framing; the S7 fault-tolerant extension is a Siemens-specific layer on top.