WinCC V8.0 STEP 7 Integration: AS-OS Engineering Benefits

1. Overview

Integrating a Siemens WinCC SCADA project directly into a STEP 7 (SIMATIC Manager) project is the standard engineering approach for plant-wide HMI/SCADA rollouts. The integration unifies the AS (Automation Station) and OS (Operator Station) into a single STEP 7 project container, eliminating parallel data administration in WinCC Explorer and the S7 program.

For a multi-line production plant with 15+ clients and redundant servers, the integrated approach provides three primary engineering benefits documented in the Siemens WinCC V8.0 Working with WinCC manual (ID 109818253):

• Simple transfer of tags and texts from STEP 7 symbols into the WinCC database.
• Direct access to STEP 7 symbol table entries during process connection configuration.
• Uniform message configuration shared between AS and OS via Alarm_8P.

2. Integration Architecture

In an integrated project, the WinCC station is a child object of the STEP 7 project tree. The structure is:

SIMATIC Manager
└── Plant_Project (S7 project)
    ├── Station_1 (S7-400 AS)
    │   ├── S7 Program
    │   │   ├── Symbol Table (S7_m_c, S7_string_0, S7_unit, S7_server)
    │   │   ├── Blocks (FB/FC/DB + Alarm_8P instances)
    │   │   └── ...
    │   └── Hardware
    ├── Station_2 (S7-400 AS)
    ├── WinCC_Server_Redundant (OS)
    │   ├── Computer (Server1, Server2, 15 Clients)
    │   └── Tag Management / Alarm Logging / Graphics
    └── Shared Data (text libraries, archive DBs)

The OS node holds the full WinCC Explorer project: tag management, alarm logging, user administration, graphics designer, and the server-client topology. All editable from a single engineering station.

3. AS-OS Engineering: Automatic Tag Generation

When the WinCC project is a child of the STEP 7 project, the WinCC tag management can import tags directly from the S7 symbol table using system attributes. This is the single largest time-saver in AS-OS engineering.

3.1 Required Symbol Attributes

Once the attributes are filled in, the engineer selects WinCC > Tools > AS-OS Engineering > Generate Tags. WinCC walks the S7 symbol table and creates the matching tag entries (data type, address, server assignment) without manual entry.

3.2 Filter Mechanism

To control which symbols are exported, the S7_m_c attribute acts as a filter — symbols without a value in S7_m_c are not imported. This is the recommended convention: do not use wildcard import, declare explicitly.

4. Alarm Configuration with Alarm_8P

For S7-300/400 systems, the Alarm_8P function block (located in the standard STEP 7 library, typically under Standard Library > System Function Blocks) is the canonical AS-OS message interface. Each instance generates up to 8 messages with acknowledgment support and associated process values.

4.1 Typical Instance in OB1 / Cyclic OB

CALL "Alarm_8P", DB100  // Alarm_8P instance DB
  EV_ID     := W#16#0001
  SIG_1     := TRUE         // Signal bit 1
  SIG_2     := FALSE
  SIG_3     := FALSE
  SIG_4     := FALSE
  SIG_5     := FALSE
  SIG_6     := FALSE
  SIG_7     := FALSE
  SIG_8     := FALSE
  SD_1      := MW20          // Associated value 1
  ...
  ACK_STATE := MW30

When the block is compiled, the message text, class, trigger, and associated values are written to the STEP 7 message configuration. After WinCC integration, the OS automatically picks up the message via AS-OS Engineering > Generate Messages — no manual re-entry in Alarm Logging.

4.2 Centralized Message Database

Because the message text and class live in the STEP 7 side, a single source of truth is maintained. Renaming a message in the S7 project and re-running Generate Messages updates all 15 clients. This is critical for plants where message text is part of regulatory documentation and must remain traceable across the project lifecycle.

5. Centralized Project Management

With integration, the entire S7 + WinCC project is one database on the project server. The following operations become single-click from one engineering workstation:

6. Server-Client Configuration via STEP 7

The WinCC server-client topology is configured inside the integrated OS node. The recommended approach for a 15-client, redundant-server plant:

1. Open the Computer property of the WinCC station in SIMATIC Manager.
2. Add two Server entries (e.g. WINCCSRV01, WINCCSRV02) for redundancy. Mark both as servers; tick Server is a preferred server for the primary.
3. Add 15 Client entries. For each client, set the startup list to the server data package of the assigned server (primary preferred, fallback to redundant).
4. Define the Standard Client in the Type column — all 15 clients reference the same client project type (see Section 8).
5. For each client, the Computer Properties > Startup tab defines the WinCC startup list: graphics runtime, message logging, user administrator, etc.

7. Client Status Monitoring

A frequent question during the design phase: "Can the server see the live state of each client?"

Yes. Two methods exist:

7.1 Tools → Status of Clients

In WinCC Explorer on the server, navigate to Tools → Status of Clients. This window displays every client currently logged into the server, showing:

• Client computer name
• Connection state (online / offline / lost)
• Logged-in user (if user administrator is active)
• Runtime active screens

This is the correct method for live monitoring — it does not require the client to be listed under the Computer list of the server's WinCC project. The Computer list is a configuration view, not a runtime status view.

7.2 The Computer List — Configuration vs. Runtime

The computer list visible in WinCC Explorer on the server shows the configured clients (the project topology), not the runtime state. Misinterpreting this list as a status display is a common source of confusion. The Status of Clients tool is the authoritative runtime view.

8. Standard Client Concept

For a fleet of 15 identical operator stations, Siemens recommends the Standard Client model:

1. Configure one Client_Type project with all graphics, alarm views, and scripts that every client should run.
2. In the server's WinCC project, reference the standard client in the Computer Properties > Type of each of the 15 client computers.
3. The server generates a Server Data package from its project and pushes it to each client at startup. The client downloads its configuration from the server's package — no separate client project download is required.

Operational impact:

• A change to graphics or alarm filtering on the server is automatically distributed to all 15 clients at the next server data refresh.
• Replacing a defective client PC requires only assigning its computer name to the Standard Client type and pointing at the server — no separate WinCC project install on the client beyond the WinCC Runtime license.

9. Redundant WinCC Server Setup

For the plant-wide rollout described, redundancy is implemented at the WinCC server layer using the SIMATIC WinCC Redundancy option (license required). Behavior:

Configuration details:

• Enable redundancy in Computer Properties > Redundancy on both servers.
• Define the archive synchronization path and partner server.
• Configure the switchover time (typical: 3–10 s depending on tag count and network).
• Validate the redundant license is installed on both servers.

10. Project Structure Recommendations for Multi-Line Plants

For a plant divided into multiple S7 projects (one per production line), the recommended topology is:

• One master STEP 7 project per line, each containing its own AS program, symbols, and Alarm_8P instances.
• One plant-wide STEP 7 project that contains only the OS node (WinCC server + clients). This OS node references the line S7 projects via the AS-OS Engineering cross-project link.
• The master project acts as the engineering container; the OS node pulls tags and messages from all line projects during Generate Tags / Generate Messages.

This is the structure that keeps the 15 clients and 2 servers consistent across the plant without duplicating the S7 logic into a single project (which would create commissioning bottlenecks and merge organizational ownership boundaries).

11. Verification & Commissioning

1. Symbol attribute audit: Open the S7 symbol table of each line project. Confirm every WinCC-relevant symbol has a populated S7_m_c value. Symbols without it will be silently skipped during tag generation.
2. Tag generation log: After AS-OS Engineering > Generate Tags, review the log file for skipped symbols, address conflicts, and type mismatches.
3. Message generation log: After Generate Messages, verify each Alarm_8P instance produced the expected number of messages in WinCC Alarm Logging.
4. Connection test: In WinCC Explorer, run Tools → Connection Status for each AS-OS link. All S7 connections should report OK.
5. Client status check: From the server, open Tools → Status of Clients and confirm all 15 clients register online after they are powered up.
6. Redundancy test: Power down WINCCSRV01 and verify WINCCSRV02 takes over within the configured switchover window. Verify clients reconnect without operator action. Restore WINCCSRV01 and confirm archive resync completes.
7. Archive integrity: On the redundant server, verify tag and alarm archives are continuously mirrored. A gap indicates the partner server connection is broken.

12. Troubleshooting Matrix

FAQ