Configuring WinCC Flexible Runtime with Two PLC Access Points

Overview

WinCC Flexible Runtime can communicate with two (or more) SIMATIC PLCs over distinct physical media at the same time. The architectural constraint is not that a single access point must be reused for both PLCs, but that each logical connection in the WinCC Flexible project must be bound to a uniquely named access point in the PG/PC interface. A working field configuration is: PLC #1 (S7-315-2 DP) on MPI to a CP 5611, and PLC #2 (S7-414-3 PN/DP) on Industrial Ethernet to the on-board NIC of the HMI panel — both visible in the running runtime, both cycling their tags. This article documents the configuration path, the constraints imposed by the PG/PC access-point scheme, and the verification checklist that confirms a healthy dual-link runtime.

The WinCC Flexible 2008 Runtime manual is the authoritative source for the access-point handling described here. See the Siemens WinCC flexible 2008 Runtime User Manual for the full description of access-point assignment and connection parameters. Companion material is available on the Siemens Industry Online Support portal.

Architectural Background: Access Points in SIMATIC

An "access point" in SIMATIC terminology is a logical name (such as S7ONLINE) that is bound to a specific physical interface and protocol. The PG/PC interface tool (Set PG/PC Interface) maintains a table that maps access-point names to interface parameters. When WinCC Flexible Runtime starts a connection, it resolves the access point name to a real driver and opens the channel.

By default, the installer creates one access point called S7ONLINE bound to the first available MPI/Profibus/Ethernet driver. If you only have one PLC, this is sufficient. If you need two PLCs on different media, the same access point cannot carry two different protocol bindings simultaneously — it must be unique per channel. The solution is to create a second access point with a different name, bind it to a different interface, and then point each WinCC Flexible connection to its corresponding access point.

Prerequisites

Before you begin, confirm that the following hardware and software are available and licensed:

• WinCC Flexible 2008 SP5 (or later SP) installed on the engineering station, plus the matching Runtime license for the target panel (e.g., WinCC Flexible 2008 Runtime, part number 6AV6.1-1KA01-0AA0 for a 128-Power-Tag runtime).
• Two SIMATIC PLCs configured with their own station addresses — typical combinations: S7-300 / S7-400, S7-200 (via EM 277 on Profibus), or ET 200S station.
• At least two distinct PC interface hardware paths: a CP 5611 / CP 5612 / CP 5621 (PCI) for MPI or Profibus, plus an on-board Ethernet NIC or a CP 1612 / CP 1623 for Industrial Ethernet. The Siemens Industry Online Support portal lists compatible PC interface cards per HMI panel type.
• Administrative rights on the engineering PC and on the runtime panel to install or remove interface drivers and to write to %ProgramFiles%\Siemens\Automation\PGPC configuration files.
• The "Set PG/PC Interface" shortcut on the Control Panel (or accessible via Start > SIMATIC > PG/PC Interface).
• STEP 7 V5.5 (for S7-300/400 side) or TIA Portal V13 or later (for S7-1200/1500 side), with active S7 connection resources to the HMI partner.

Step-by-Step: Adding a Second Access Point

The configuration sequence below produces two named access points — one for MPI and one for TCP/IP Ethernet — on the same engineering or runtime PC.

Step 1 — Open the PG/PC Interface Tool

From the Windows Start menu, choose SIMATIC > PG/PC Interface. The dialog opens with the current access-point list. By default you will see S7ONLINE bound to the first installed driver.

Step 2 — Add a New Access Point

1. In the "Access Point of the Application" dropdown, click the selection arrow and choose Add....
2. Enter a descriptive name, for example S7ONLINE_MPI for the MPI access point, and confirm with OK.
3. Repeat to add a second access point, for example S7ONLINE_TCPIP for the Ethernet channel.

Step 3 — Bind the First Access Point to the MPI Interface

1. Select S7ONLINE_MPI in the dropdown.
2. In the "Interface Parameter Assignment Used" list, choose CP 5611(MPI) (or your installed MPI/Profibus card and the correct protocol, e.g., CP 5612(Profibus)).
3. Open Properties..., set the local MPI address (default 0 for the PG/PC), the transmission rate (187.5 kbps is the standard MPI default, 1.5 Mbps for Profibus), and the highest station address (default 31 for MPI, 126 for Profibus).
4. Click OK to apply.

Step 4 — Bind the Second Access Point to the Ethernet Interface

1. Select S7ONLINE_TCPIP.
2. Choose TCP/IP > Network Card (Industrial Ethernet) as the assigned interface. Make sure the Industrial Ethernet variant is selected, not the standard NDIS WanIP driver.
3. In Properties..., verify that the IE-PG access is enabled. No IP address is configured at the PC interface level — that is handled on the PLC side (PN/DP CPU or CP 343-1/CP 443-1).
4. Click OK to apply.

Step 5 — Confirm the Table

The PG/PC interface dialog should now list two rows (or two entries under the same access point with different bindings, depending on the driver version). Close with OK and restart the WinCC Flexible Runtime to pick up the new bindings.

Configuring the WinCC Flexible Project

Once the access points exist, the WinCC Flexible project must be wired to use them.

Open the Connections Editor

In the WinCC Flexible ES project tree, navigate to Project > Connections (German UI: Projekt > Verbindungen). The Connections editor opens as a table where each row represents one logical S7 connection from the HMI to a PLC.

Add Two Connections

1. Double-click the first empty row. The "Connection Properties" dialog opens.
2. Set Name: Connection_1 (or any descriptive name, e.g., Line1_S7_300).
3. Set Communication driver: S7 MPI/DP for an MPI/Profibus link, or S7 Ethernet (ISO/TCP) for Industrial Ethernet.
4. Set HMI device: select the panel that will host the runtime (e.g., MP 377, TP 177B).
5. Set Access point: in the dropdown, choose the access-point name that matches the chosen driver — S7ONLINE_MPI for the MPI connection.
6. Set the PLC parameters: PLC address (MPI/PB station number, e.g., 2), Slot (rack/slot of the CPU, e.g., 0/2 for an S7-300 CPU 315-2 DP in slot 2), and any rack number for S7-400.
7. Click OK to commit.
8. Repeat for the second PLC, choosing S7ONLINE_TCPIP as the access point and the matching Ethernet driver.

PLC-Side Configuration (STEP 7 / TIA Portal)

The PLC side must permit the S7 connection from the HMI. With STEP 7 V5.5, open the S7-300 / S7-400 station and load the connection table from the HMI's downloaded configuration (via PLC > Edit Ethernet Node or NetPro > Insert Connection). For the MPI partner, the HMI appears as an "active" S7 partner and the local ID 1 is the matching S7 connection. For the Ethernet partner, configure an S7 connection with "Unspecified" partner, enter the HMI's IP address, the same local ID, and a single-Rack single-Slot partner port (rack 0, slot 0 for a panel with no slot concept, or the appropriate slot for an HMI station with a configured slot).

If you use TIA Portal to configure the S7-1500 / S7-1200 side, add an HMI connection in Devices & Networks > Connections with the panel selected as the partner and the "S7 connection" type. Enable the connection as "Establish active connection" if the HMI initiates it.

Compilation, Transfer, and Runtime

1. Compile the WinCC Flexible project (Project > Compiler > All) and verify zero errors in the output window.
2. Transfer the runtime to the panel using Ethernet, Profibus, MPI, or USB (depending on panel) — Project > Transfer > Transfer.
3. On the panel, enter Transfer mode and complete the transfer.
4. Exit Transfer mode; the runtime starts. Open Start > Control Panel > HMI Diagnostics on the panel (or use the diagnostics screen in the project) and verify that both connections show Online.

Verification Checklist

Troubleshooting Matrix

Edge Cases and Field-Proven Caveats

Same physical CP, two access points. A CP 5611 can theoretically carry both MPI and Profibus on different logical channels, but the standard configuration expects one protocol binding per access point. If you need MPI on PLC 1 and Profibus on PLC 2 from a single CP 5611, you must create two access points bound to the same CP but with the protocol selected as MPI in one and Profibus in the other — the firmware switches automatically. In practice, two separate PC interface cards (one CP 5611 + one CP 1612) give better isolation and easier diagnostics.

MP 277 / MP 377 with on-board MPI/DP and Ethernet. Most Multi Panels expose a Profibus/MPI port and an Ethernet port on the underside. The on-board Ethernet is typically the second access point's binding; the on-board MPI/DP is the first. No additional hardware is required.

Mobile panels with wireless. Mobile Panel 277 IWLAN uses an Industrial Wireless LAN access point, not a direct Ethernet cable. The access point must be bound to the WLAN NIC and the PLC partner's IP must be reachable from the WLAN subnet.

Mixing S7-200 with S7-300/400. S7-200 connects only through Profibus (via EM 277) or Ethernet (via CP 243-1). It is not an MPI/DP native device. The WinCC Flexible connection to an S7-200 must use the S7 200 (EM 277 / CP 243-1) driver and an access point bound to the right Profibus or Ethernet channel.

Multiple connections on the same PLC. You can have more than one connection from a single HMI to a single PLC (e.g., a fast-process-tag channel and a slow-diagnostic channel). Each connection must still have a unique access point binding, and the PLC side must allocate the matching S7 connection resources.

Migrating to TIA Portal (WinCC Comfort/Professional)

WinCC Flexible 2008 was the last release in the WinCC Flexible product line. New projects should be created in TIA Portal with WinCC Comfort (for Comfort Panels) or WinCC Professional (for WinCC Runtime Advanced / Professional). The two-access-point pattern is preserved: each HMI connection in the project is bound to a specific PG/PC Interface entry, and the migration tool maps the original access-point names to the new ones automatically. Verify the migration log for the warning "Access point S7ONLINE_X not found in target system" — this means the new PC does not have the matching access point configured.

FAQ