Resolving S7 Error 8703 on S7-200 CP243-1 OPC Ethernet to WinCC

Resolving S7 Error 8703 on S7-200 CP243-1 over Ethernet to WinCC via SIMATIC NET OPC

When integrating a legacy Siemens S7-200 PLC into a modern WinCC SCADA application through a CP 243-1 Ethernet module and the SIMATIC NET OPC Server, a recurring failure pattern appears in the Station Configuration Editor diagnostic buffer:

The component is sending a negative response. TF service: 28
The component is sending a negative response. S7 error code: 8703
The component start job was refused
Component database invalid
Command STOP due to PG command

This diagnostic block is generated by the IE General module index inside the SIMATIC PC Station. The module never transitions to RUN, which prevents the SIMATIC NET OPC Server from establishing the S7 connection to the CP 243-1. The article documents the full commissioning path and isolates the configuration mismatches that produce S7 error 8703, including the partner TSAP (Transport Service Access Point) and PC Station naming rules that are required for successful CP 243-1 communication.

1. Architecture and Component Roles

The integration follows a five-layer pipeline:

1. S7-200 CPU with attached CP 243-1 on the left side of the backplane.
2. Ethernet transport - either a crossover cable or a switch. The CP 243-1 communicates at 10/100 Mbps, full duplex, on a fixed IP address configured through STEP 7-Micro/WIN's Ethernet Wizard.
3. PC NIC (Intel PRO/100 VE or equivalent) - the physical interface presented to the PC Station.
4. SIMATIC PC Station containing OPC Server (Slot 1) and IE General (Slot 2), virtualized through the Station Configuration Editor.
5. WinCC as OPC client, reading tags through the SIMATIC NET OPC DA Server V6.3.

2. Prerequisites

• STEP 7 Professional V5.4 (with installed NCM optional package for S7-200 PC Station).
• SIMATIC NET PC Software V6.3 with Hotfix 1 (installed from the WinCC V6.0 SP4 product DVD).
• STEP 7-Micro/WIN V4.0 + SP6 with Ethernet Wizard for CP 243-1 configuration.
• Softnet S7 for Industrial Ethernet runtime license, MLFB 6GK1 704-1CW63-3AA0 (V6.3) for up to 13 S7 connections, or 6GK1 704-1CW64-3AA0 for V6.4 environments.
• Administrator rights for installing the Station Configuration Editor service and changing network binding.
• A static IP scheme. CP 243-1 default is 0.0.0.0 (DHCP disabled). The PG/PC and CP 243-1 must share a /24 subnet.

3. Configure the CP 243-1 in STEP 7-Micro/WIN

1. Open STEP 7-Micro/WIN V4.0 and load the project for the CPU 226.
2. Run Tools > Ethernet Wizard. Select the CP 243-1 module position (e.g., position 1).
3. Assign the module IP address 172.27.0.2 and subnet mask 255.255.255.0.
4. Define the number of server connections (1 to 8). Each connection requires a TSAP pair.
5. Set TSAP for connection 0 to 01.01 (default) or a project-specific value; record the value because it must match NetPro.
6. Choose This is a server connection and tick Accept all connection requests only during initial testing.
7. Write the configuration to the CPU and cycle power.

Verify with Ping 172.27.0.2 from the Windows command prompt. A successful ping confirms that the CP 243-1 is alive on Layer 3; it does not prove the S7 connection works.

4. SIMATIC Manager PC Station Configuration

4.1 Create the PC Station project

1. In SIMATIC Manager, choose File > New > Project; right-click the project, choose Insert New Object > SIMATIC PC Station.
2. Open SIMATIC PC Station > Configuration to launch HW Config.

4.2 HW Config slot assignment

1. Drag OPC Server from the catalog (path: SIMATIC PC Station > User Application > OPC Server) to Slot 1. Use SW V6.0 SP4 or later.
2. Drag IE General from (SIMATIC PC Station > CP Industrial Ethernet > IE General) to Slot 2. Use SW V6.2 or later.
3. Open IE General properties: subnet = Ethernet, IP = 172.27.0.3, subnet mask 255.255.255.0. The IP must match the Windows TCP/IP binding of the NIC used for the PC Station.
4. Save and Compile. No errors should be reported.

4.3 NetPro S7 connection to CP 243-1

1. In NetPro select the OPC Server object.
2. Right-click > Insert New Connection.
3. Partner: Unspecified; type: S7 connection.
4. Properties > Address Details:
   • Partner IP: 172.27.0.2
   • Connection Resource (TSAP): 10 (hex). For CP 243-1, the TSAP encoding is two ASCII bytes; 10 corresponds to a numeric TSAP of 01.00 when the byte is interpreted as BCD pair. If the value differs from the CP 243-1 server TSAP, S7 error 8703 is raised on connect.
5. Local Interface: IE General (NOT the physical NIC name).
6. Save and Compile the NetPro configuration. Zero errors expected.

5. Configuration Console and Station Configuration Editor

1. Open Configuration Console (Start > SIMATIC > SIMATIC NET > Configuration Console).
2. Application > Select protocols. Tick only S7. Apply.
3. Modules > select the physical NIC (e.g., Intel PRO/100 VE Network Connection) > General.
   • Interface profile: TCP/IP (Auto) is recommended for CP 243-1 connections. ISO Industrial Ethernet can also be used when the S7-200 partner was configured with ISO protocol in the Ethernet Wizard.
   • Mode: Configured mode with the Station Configuration Editor index for IE General (typically Index 2).
   • Diagnostic address: keep default.
4. Apply and close.

Open Station Configuration Editor. The configured slots must mirror HW Config:

6. Download the PC Station

1. In NetPro select SIMATIC PC Station > PLC > Download to Current Project > Selected Stations.
2. If a dialog warns that the configured offline module differs from the target online module, click OK - the warning is informational.
3. If the download reports Error during complete restart of the module, proceed to Section 7 - the underlying cause is most likely S7 error 8703 raised by IE General.

7. Diagnosing S7 Error 8703 and TF Service 28

Open Station Configuration Editor, mark IE General, click Diagnostic > Diagnostic Buffer. The relevant entries for this failure mode are:

7.1 Root cause ranking

S7 error 8703 in this configuration is almost always one of the following:

1. TSAP mismatch between NetPro connection resource and the CP 243-1 server connection TSAP.
2. Station name mismatch between SIMATIC Manager and Station Configuration Editor.
3. IP/subnet mismatch between Windows TCP/IP binding and IE General HW Config property.
4. Interface profile mismatch - Configuration Console using ISO while the CP 243-1 server connection was created with TCP/IP, or vice versa.
5. Cached configuration - a previous failed download left a corrupt XDB on the PC. Stop the S7DOS service, delete %ProgramFiles%\Siemens\Automation\S7ws\S7wsvbx.XDB, and re-download.

7.2 Step-by-step remediation

1. Verify Station Name. In SIMATIC Manager, select the SIMATIC PC Station. Press Alt+Return. Compare Name against Station Configuration Editor > Station > Station name. They must be byte-identical. This was the actual root cause for the original post - renaming the PC Station to a different value resolved the issue.
2. Verify TSAP pair. Open STEP 7-Micro/WIN's Ethernet Wizard, navigate to the connection tab, and read the CP 243-1 server connection's TSAP (e.g., 01.01). Convert to the hex value expected in NetPro: the byte order in NetPro is reverse, so CP 243-1 TSAP 01.01 becomes Connection Resource = 0x0101. Enter this value in Address Details > Connection Resource. Save and Compile.
3. Verify IP settings. Windows ipconfig /all must show the NIC IP = 172.27.0.3 and mask = 255.255.255.0. HW Config IE General and Windows binding must be identical.
4. Verify Configuration Console profile. Choose TCP/IP (Auto) for general CP 243-1 use. ISO Industrial Ethernet is mandatory only if the CP 243-1's Connection Type in the Ethernet Wizard is set to ISO. Mixing the two raises transport errors during connection setup, not 8703 - but it prevents any data from flowing.
5. Reboot the PC. Hibernate is not sufficient. The Station Configuration Editor service caches the active configuration in the registry; a full restart rebuilds the COM/DCOM subsystem.
6. Re-download the PC Station. In NetPro, PLC > Download to Current Project. Confirm the IE General diagnostic buffer no longer reports 8703 and the module state is RUN.

8. Alternative Path - PC Access for S7-200 Only

If the WinCC project connects only to S7-200 stations and never to S7-300/S7-400, the S7-200 PC Access OPC server is a lighter alternative:

• Installs without SIMATIC NET and SIMATIC Manager.
• Free demo version allows up to one tag read for evaluation (full version is licensed per tag count).
• Exposes V-memory directly through a built-in V-memory browser, removing the manual TSAP configuration.

For mixed fleets, stay with SIMATIC NET OPC + Softnet S7 license. PC Access does not communicate with S7-300/400 PLCs.

9. Reading V-Memory from OPC Scout / WinCC

SIMATIC NET OPC Server exposes the S7-200 V-memory area via item paths of the form:

S7:[S7_Connection_1]V0  ; 16-bit VW0
S7:[S7_Connection_1]VD100  ; 32-bit VD100
S7:[S7_Connection_1]VB200,2  ; bit 2 of VB200 (BOOL)

To map symbolic WinCC tags without retyping each item:

1. In WinCC Explorer open the Tag Management editor.
2. Add the OPC channel driver.
3. Select OPC.SimaticNET as OPC server, browse the namespace, and assign WinCC variable names to OPC item names.
4. For STRING access, read VW0 as a length and subsequent VWs as character codes (S7-200 string handling differs from S7-300 - see Micro/WIN help "String Data Type").

10. Verification Procedure

1. Open OPC Scout V10 (Start > SIMATIC > SIMATIC NET > OPC Scout).
2. Add a server OPC.SimaticNET and connect.
3. Add an item S7:[CP243_1]VW0. Quality should be Good and the timestamp fresh.
4. Force a value in Micro/WIN (Program Status Table) and confirm the OPC value updates within 1 second.
5. In WinCC, build a graphics screen with an I/O field bound to the imported tag. Trigger a runtime test (Start > WinCC Runtime).
6. Inspect Station Configuration Editor > IE General > Diagnostic Buffer for absence of 8703/8704 events.

11. Licensing and Connection Limits

The license key is bound to the host's Automation License Manager. After installing the Softnet S7 runtime, start ALM (Start > Siemens Automation > Automation License Manager) and confirm the entry is Valid rather than Not licensed. Event log message 0x020A0001 indicates an unlicensed state and the OPC server will refuse to bring up additional connections beyond the Lean limit.

12. Troubleshooting Matrix

13. Field-Proven Caveats

• Hibernate does not reset the Station Configuration Editor. A real shutdown + power-on is required after any change to the IE General or OPC Server index.
• SW version mismatch between HW Config and S7DOS service produces 8703 errors even when the TSAP is correct. Align to SW V6.2 on IE General and SW V6.0 SP4 on OPC Server for SIMATIC NET V6.3.
• Windows firewall on XP SP2+ silently blocks DCOM and OPC enumeration. Add the OPC Server process (S7OPCSX.exe) to the firewall exception list.
• V-memory access from Micro/WIN while OPC is active can stall the S7 connection briefly because the CP 243-1 serializes requests. Use a polling rate of at least 500 ms in WinCC to avoid timeout-driven Bad quality.
• STEP 7 V5.4 SP4 + Windows XP SP2 is the last validated combination for this integration. Migrating to Windows 7 requires SIMATIC NET V7.0+ and the CP 243-1 IT (6GK7 243-1GX00-0XE0) or CP 243-1 (6GK7 243-1EX01-0XE0) firmware V2.0 or later.

14. References Inside This Article

• SIMATIC NET S7 OPC Server - Programming and Operating Manual
• Commissioning PC Station with SIMATIC NET (Application Example)
• Accessing S7-200 V-Memory via OPC - Application Note
• CP 243-1 Product Manual (6GK7 243-1EX01-0XE0)
• S7-200 PC Access V1.0 SP6 - Operating Manual

Frequently Asked Questions