Connecting S7-200 SMART to Redundant PCS 7 WinCC OS Servers via Ethernet

To connect an S7-200 SMART CPU ST60 to a redundant SIMATIC PCS 7 V8.1 WinCC OS Server over Ethernet TCP/IP, configure the connection under the 'SIMATIC S7 Protocol Suite -> TCP/IP' channel using custom TSAP addressing instead of standard S7-400 rack/slot parameters. The default rack/slot connection fails because S7-200 SMART operates as an S7 server using Transport Service Access Points (TSAPs). In WinCC Connection Properties, set the Remote TSAP to 02.00 (or 03.00) and Local TSAP to 02.00, with Rack 0 and Slot 1. For redundant OS Servers, configure identical TCP/IP connections pointing to the CPU ST60 IP address on both Master and Standby servers.

S7-200 SMART Communication Architecture and Protocol Limitations

The SIMATIC S7-200 SMART series (such as CPU ST60) is an economical compact PLC with an integrated PROFINET / Ethernet port. While designed primarily for small machine automation, engineers frequently need to integrate package units (e.g. water treatment skids, chemical dosing packages) into a centralized SIMATIC PCS 7 DCS environment.

Attempting to connect S7-200 SMART directly into WinCC via the standard PCS 7 AS-OS compilation workflow fails because the S7-200 SMART is not an S7-400 controller, does not support Continuous Function Chart (CFC), and cannot be compiled via SIMATIC Manager. Communication must be established manually in WinCC Tag Management using native communication channels or fieldbus gateways.

Configuring S7 Protocol Suite with RFC 1006 TSAP Addressing

The most direct communication path uses the WinCC SIMATIC S7 Protocol Suite via Industrial Ethernet / TCP/IP:

S7-200 SMART CPU Settings: In STEP 7-Micro/WIN SMART, configure the CPU ST60 IP address (e.g. 192.168.1.50). Ensure PUT/GET communication is enabled in system block protection settings.
WinCC Tag Management Configuration:
- On the WinCC OS Server, open Tag Management.
- Add the communication channel SIMATIC S7 Protocol Suite.
- Under TCP/IP, right-click and select New Connection....
- Name the connection (e.g. S7_200_ST60).
Connection Properties and TSAP Assignment:
- Enter the IP address of the CPU ST60.
- Standard S7-400 connections use Slot 2 or Slot 3. For S7-200 SMART, switch addressing to TSAP.
- Set Remote TSAP to 02.00 (or 03.00 depending on the connection slot configured in Micro/WIN SMART).
- Set Local TSAP to 02.00 (or 01.00).
- Set Rack to 0 and Slot to 1.
Variable Addressing: Address process tags directly using S7 memory areas (e.g. DB1,DBD0 mapped to V-memory VD0, since V-memory in S7-200 corresponds to DB1 in classic S7 communication).

Alternative Integration Strategies: Modbus TCP and OPC DA/UA

If S7 protocol communication is constrained or network segmentation prohibits direct S7 connections, three alternative architectures are available:

Modbus TCP: S7-200 SMART supports native Modbus TCP Server instructions (MBUS_SERVER) in Micro/WIN SMART. In WinCC, use the Modbus TCPIP channel to map holding registers (40001+) directly to WinCC tags.
OPC DA / UA via PC Access SMART: Run Siemens S7-200 PC Access SMART OPC Server. WinCC connects to the OPC server using the standard WinCC OPC Channel (OPC.DA / OPC.UA), abstracting PLC communication completely.
Hardwired I/O to PCS 7 ET 200 Stations: For safety-critical interlocks or critical status signals, hardwire digital/analog outputs from the ST60 directly into ET 200M/ET 200SP I/O modules connected to the PCS 7 AS-410 controller, allowing standard APL driver block generation.

Redundant OS Server Architecture for Standalone Micro-PLCs

Because S7-200 SMART lacks redundant Ethernet communication interfaces, integrating it with a redundant OS Server pair (OS Server Master and OS Server Standby) requires specific handling:

Independent Parallel Connections: Configure the TCP/IP connection in WinCC Explorer on the Engineering Station. When the project is downloaded to both redundant servers, both OS Master and Standby establish independent, concurrent TCP/IP connections to the single IP address of the ST60.
Connection Monitoring: CPU ST60 supports up to 8 simultaneous S7 connections. Two connections allocated to the OS servers leave ample connection resources for local HMIs (e.g. SmartLine panels) and engineering laptops.

Communication Method Comparison Matrix for S7-200 SMART

The following table compares different integration methods for connecting S7-200 SMART to SIMATIC PCS 7 WinCC OS:

Integration MethodCommunication ProtocolRequired WinCC ChannelConfiguration ComplexityRedundancy SupportDirect S7 Protocol (Recommended)S7 Protocol over RFC 1006SIMATIC S7 Protocol Suite (TCP/IP)Low (TSAP 02.00 configuration)Both OS servers connect concurrentlyModbus TCPOpen Modbus TCPModbus TCPIP ChannelModerate (PLC code requires MBUS_SERVER)Dual server connections supportedOPC ServerOPC DA / OPC UAWinCC OPC ChannelModerate (Requires PC Access SMART software)Single-point-of-failure at OPC serverHardwired I/O to AS24V DC Digital / 4-20mA AnalogPCS 7 APL Channel DriversHigh cabling; zero software riskInherits full AS and OS redundancy

[!NOTE]
Commercial Accuracy Notice: Communicating third-party or micro-PLCs (such as S7-200 SMART CPU ST60) directly into WinCC > Tag Management consumes standard WinCC external runtime tags (6ES7658-2CX58-0YH5). Tags connected directly to WinCC > without an AS-400 controller do not consume PCS 7 AS Runtime Process Objects (AS RT POs).

Verification

Confirm successful data exchange between S7-200 SMART and the WinCC OS Servers:

Channel Diagnosis Tool: On the WinCC OS Server, launch WinCC Channel Diagnosis (WinCCChannelDiagnosis.exe). Expand SIMATIC S7 Protocol Suite -> TCP/IP. Verify that the connection status displays a green checkmark (Status: OK).
Live Tag Updating: Create a test tag linked to V-memory (e.g. DB1,DBD0). Display the tag on a graphic PDL and confirm that values update cyclically in runtime.
Dual Server Test: Verify that both redundant OS servers display healthy connection status simultaneously without dropping packets.

Limitations and Operational Precautions

Observe these operational boundaries when integrating micro-PLCs into PCS 7:

No Centralized Time Synchronization: S7-200 SMART cannot participate in PCS 7 AS-wide high-precision time synchronization (clock synchronization via SIMATIC mode). Alarm timestamps reflect the OS Server arrival time.
No APL Driver Generation: Because logic resides in the S7-200 SMART, PCS 7 automatic driver generation (Generate module drivers) and Maintenance Station diagnostics do not apply.
Network Segmentation: Isolate package unit networks from the high-speed PCS 7 Plant Bus using a managed switch or VLAN to prevent broadcast flooding.

Engineer FAQ

Why did my TCP/IP connection to S7-200 SMART fail with standard settings?

Standard S7 connections in WinCC target S7-300/400 controllers using Rack and Slot addressing. S7-200 SMART requires RFC 1006 TSAP addressing (Remote TSAP 02.00, Local TSAP 02.00).

How does S7-200 V-memory map to WinCC DB addressing?

In S7-200 and S7-200 SMART communication, V-memory is addressed as Data Block 1 (DB1). For example, double word VD100 is addressed in WinCC as DB1,DBD100.

Can S7-200 SMART handle connections from both redundant WinCC servers?

Yes. The CPU ST60 supports up to 8 simultaneous Ethernet connections, easily accommodating concurrent links from both redundant OS Servers and local operator panels.

Do tags created directly in WinCC consume PCS 7 Process Objects?

No. Tags created manually in WinCC Tag Management consume WinCC external archive/runtime tags, but they do not consume PCS 7 AS Process Object (PO) licenses because no AS-400 CFC blocks are involved.