Troubleshooting Profibus Routing Siemens CPU 414-2, ET 200M

1. System Overview and Typical Failure Mode

A common commissioning scenario pairs a SIMATIC S7-400 CPU 414-2 with a distributed ET 200M station on Profibus DP and a MP 377 Multi Panel for HMI. When the programming device (PG/PC), the PLC, the ET 200M, and the panel are all connected on different physical networks, transfers from WinCC Flexible 2008 SP2 fail with the dialog "Enable routing" not appearing, the touch panel stays unreachable, or the CPU reports a BUSF (Bus Fault) and EXTF (External Fault) LED combination. The root cause in nearly every case is not a cable, hardware, or Profibus termination problem but a misconfigured PG/PC interface assignment in the SIMATIC Manager combined with missing NetPro routing entries.

The architecture most often described is:

• S7-400 CPU 414-2 with the integrated Profibus DP master (interface X2) on the Profibus segment.
• ET 200M with an IM 153-1 / IM 153-2 / IM 153-4 interface module as a Profibus DP slave on the same segment.
• MP 377 15" Touch (6AV6 644-...) either on Profibus (rare) or on Ethernet (recommended).
• PG/PC with a CP 5611 / CP 5613 / CP 5711 Profibus card and an Ethernet card for TCP/IP.
• A CP 443-1 (e.g., 6GK7 443-1EX11) Ethernet communications processor providing the routing gateway between the engineering subnet and the Profibus subnet.

2. Hardware Identification and Module Part Numbers

Confirm the exact catalog numbers before commissioning, because LED behavior, Profibus diagnostics buffer text, and supported GSD revisions all vary by hardware release.

ET 200M uses the I/O module catalog of the S7-300 automation system (SM 321 / SM 322 / SM 331 / SM 332 / SM 334 / FM / CP). For full configuration guidance see the Siemens documentation for ET 200M configuration in TIA Portal.

3. Decoding the BUSF and EXTF LED Patterns

On an S7-400 CPU, the front-panel LEDs are the fastest way to localize a Profibus problem before opening the diagnostics buffer.

When the engineer sees BUSF flashing with EXTF on on the CPU and no BF on the ET 200M, the affected slave is almost always the MP 377 panel (because it is the only Profibus node that is not properly initialized in the project).

4. Root Cause Analysis: Why "Enable Routing" Disappears

WinCC Flexible 2008 / TIA Portal shows the "Use routing" check box in the transfer dialog only when three preconditions are simultaneously met:

1. PG/PC interface (S7ONLINE access point) is bound to a TCP/IP-capable Ethernet card, not to a Profibus CP and not to an ISO protocol.
2. NetPro contains a valid subnet gateway relationship from the PG/PC's Ethernet subnet, through the CP 443-1, to the Profibus subnet where the MP 377 lives.
3. The WinCC Flexible project has the HMI station connected over the same subnet as the PG/PC or via a routable gateway; otherwise the routing check box is suppressed.

If the engineer assigns the Profibus CP (CP 5611 / CP 5613) to S7ONLINE with the ISO protocol, the routing tick box never appears because the routing logic is a property of the TCP/IP stack. Likewise, setting the CP 5611 as PC internal while the Ethernet is selected as the active interface hides the routing path. Switching the access point assignment and protocol clears the symptom in roughly 90 percent of the cases reported.

5. PG/PC Interface Configuration (S7ONLINE Access Point)

The single highest-leverage setting in the whole setup is the PG/PC interface assignment. Use the Windows control panel applet "Set PG/PC Interface" (in SIMATIC Manager: menu Options > Set PG/PC Interface).

1. Open Start > SIMATIC > SIMATIC Manager > Options > Set PG/PC Interface.
2. For Application access point: select S7ONLINE.
3. For Interface parameterization used: select TCP/IP → <your Ethernet NIC>.
4. Click OK, close the dialog, and restart WinCC Flexible Transfer.

6. NetPro Routing Configuration

Routing is configured graphically in NetPro within the SIMATIC Manager. The CPU, CP 443-1, MP 377, ET 200M, and PG/PC station must all live in the same STEP 7 project, and each subnet must be connected with subnet gateway relationships.

1. In HW Config, drag a CP 443-1 into the S7-400 rack and configure its IP address and Ethernet subnet. Connect it to a new or existing Ethernet subnet object.
2. Open NetPro (the button next to HW Config) and verify that the CP 443-1 port is connected by a line to the Ethernet subnet, and the CPU's Profibus port is connected to the Profibus subnet.
3. Drag the MP 377 from the hardware catalog into the Profibus subnet (or the Ethernet subnet if migrating to Ethernet).
4. Drag the ET 200M into the Profibus subnet and assign a unique DP address.
5. Add the PG/PC station and assign it to the Ethernet subnet with the same TCP/IP driver as in Set PG/PC Interface.
6. Right-click each network connection and confirm that Properties > Options shows the "Router" entries pointing at the CP 443-1 (i.e., the CP is the gateway).
7. Compile and download NetPro to the S7-400 station (PLC > Download > to Target System).

Without these steps, WinCC Flexible sees the MP 377 as off-net and refuses to offer routing.

7. ET 200M with IM 153-x: Profibus Slave Setup

The ET 200M takes the place of a remote rack on Profibus. Configuration steps:

1. From the hardware catalog select PROFIBUS DP > ET 200M > IM 153-1 / IM 153-2.
2. Drag it onto the Profibus subnet in HW Config or NetPro.
3. Assign a DP address that is unique on the segment (default is 3; avoid address 0, 1, 2 reserved by the master).
4. Plug the same module types (SM 321 DI, SM 322 DO, SM 331 AI, SM 332 AO) into the IM 153 slots that are physically mounted in the field.
5. Match the IM 153 hardware version with the GSD file used; mismatches trigger SF on the IM and EXTF on the CPU.

Detailed topology is documented in the Siemens reference for connecting an ET 200M to a STEP 7 project and in ET 200M configuration.

8. MP 377 Transfer Mode and IP Configuration

The MP 377 has two transfer paths: Profibus DP at the panel's PROFIBUS port, or Ethernet at the panel's LAN port. For Ethernet transfer:

1. Power up the MP 377 and enter the Control Panel: Start > Settings > Control Panel.
2. Tap Transfer and ensure Enable Channel is on, Remote Control is on, and the timeout is non-zero.
3. Open S7 Transfer Settings and pick Ethernet (TCP/IP).
4. Open Network & Dial-up Connections > LAN and configure a static IP in the same subnet as the CP 443-1 and PG/PC (e.g., 192.168.0.40 / 255.255.255.0).
5. From the PG/PC run ping 192.168.0.40. If ping fails, the panel is offline.
6. Force the panel into transfer mode either by selecting Transfer in the loader, or by ticking Remote Control in the Control Panel so the HMI accepts the transfer from WinCC Flexible automatically.

For Profibus DP transfer, set the panel's Profibus address and baud rate to match the CPU 414-2 (typically 1.5 Mbit/s) and ensure the DP cable is terminated at both ends (ON / OFF switch on the panel's Profibus connector).

9. WinCC Flexible Transfer Procedure with Routing

Once the S7ONLINE access point is TCP/IP and NetPro has the CP 443-1 routed to Profibus:

1. Open WinCC Flexible 2008 SP2 and load the project.
2. Select Project > Transfer > Transfer Settings.
3. Choose Ethernet as the mode and enter the MP 377's IP address.
4. Tick Enable routing — this is the check box that previously did not appear.
5. Tick Display all accessible nodes and click Search. The MP 377 should appear even though it sits behind the CP 443-1 on a Profibus subnet.
6. Select the panel and click Transfer.

10. Why Ethernet Is Preferred over Profibus for the MP 377

Putting the MP 377 on Ethernet instead of Profibus DP solves the routing problem and improves performance.

Because the panel polls many tags per second, putting it on Profibus extends the DP cycle and can push the ET 200M beyond its target update time. Ethernet isolates that traffic.

11. Step-by-Step Commissioning Procedure

Use this ordered procedure to take a project from "blank" to "running".

1. Build hardware: Insert CPU 414-2, CP 443-1, ET 200M (IM 153-x), and MP 377 in HW Config.
2. Configure Profibus: assign the DP master system, set the baud rate (1.5 Mbit/s), and assign DP addresses (CPU default 2, ET 200M e.g., 3, MP 377 e.g., 4).
3. Configure Ethernet: set the CP 443-1 IP, MP 377 IP, and PG/PC IP in the same subnet.
4. Build NetPro: drag all stations onto the correct subnets and verify that the CP 443-1 routes from Ethernet to Profibus.
5. Integrate the WinCC Flexible project into the STEP 7 project (Options > WinCC Flexible Integration in SIMATIC Manager).
6. Compile and download both the STEP 7 station (with NetPro) and the HMI station. If RTM errors appear, rebuild all.
7. Set PG/PC interface: S7ONLINE = TCP/IP → Ethernet NIC.
8. Enable transfer mode on the MP 377 and ping its IP from the PG/PC.
9. Transfer WinCC with Enable routing ticked.
10. Verify I/O: monitor the ET 200M inputs in a VAT table and confirm BUSF / EXTF LEDs on the CPU are off.

12. Verification Checklist

13. Troubleshooting Matrix

14. Recommended Best Practices

• Always migrate the MP 377 to Ethernet unless a Profibus cable is already part of an approved installation plan.
• Use a single CP 443-1 as the routing gateway; do not add multiple Ethernet CPs unless required for redundancy.
• Always load empty OBs (OB82, OB86, OB121, OB122) into the S7-400 program so DP diagnostics do not STOP the CPU.
• Pin the PG/PC's Ethernet IP to a fixed value rather than DHCP to make NetPro and WinCC consistent.
• Document Profibus addresses in a label on the panel and IM 153; mismatched addresses are the single most common commissioning error.
• When migrating between STEP 7 / WinCC Flexible 2008 SP2 and TIA Portal, recreate NetPro rather than copy-paste; the routing data structures changed.