Configuring CPU315-2DP Ethernet SCADA via CP343-1 Lean

System Overview and Migration Rationale

The Siemens SIMATIC S7-300 CPU 315-2DP (order number 6ES7 315-2AG10-0AB0 or current -2AH14 variant) is a workhorse controller for mid-size automation, including residential and light-commercial control loops. It ships with an integrated MPI/DP interface on the first X1 port and a separate DP master/slave port on X2, but no native Ethernet. When the original HMI/SCADA layer is a CE6 panel connected via the legacy PC Adapter USB A2 (6ES7 972-0CB20-0XA0) on MPI, the architecture is functional but constrained: MPI runs at 187.5 kbit/s or 1.5 Mbit/s, the panel is short on CPU/RAM, and modern tablets running Windows 10/11 cannot reliably install the legacy PC Adapter drivers on USB 3.0 controllers.

Adding a CP 343-1 Lean (6GK7 343-1CX10-0XE0) gives the S7-300 station a 10/100 Mbit Ethernet port that exposes the S7 protocol to any TCP/IP-capable SCADA host. The CP supports S7 communication, PG/OP communication, ISO-on-TCP (RFC1006, port 102), TCP, UDP, and a built-in web server for diagnostics. The Lean variant deliberately omits PROFINET controller functionality and the IT diagnostics of the Advanced (6GK7 343-1GX30-0XE0), but for SCADA polling it is more than sufficient and roughly 40 percent lower in cost.

Prerequisites and Bill of Materials

Before touching any hardware, confirm that the Movicon 11.5 installation media contains the Siemens S7 TCP/IP driver (DLL ss7_tcp.dll or SiemensS7TCP.dll depending on build). The driver is normally bundled with the standard Movicon build for industrial use; it is not a separate license and supports both S7-300 and S7-400 racks.

Hardware Architecture: Adding the CP 343-1 to the S7-300 Rack

The S7-300 backplane is slot-numbered, and the CP must be placed in a free signal-module slot. The standard layout for a CPU 315-2DP system with one CP is:

The CP occupies slot 4 and consumes 24 V from the backplane. Each CP reserves 16 bytes of input and 16 bytes of output in the process image (addresses PE 0…15 and PA 0…15 in slot 4), but these are internal and should not be referenced from the user program. They appear automatically in the hardware configuration of STEP 7.

STEP 7 Hardware Configuration

Open SIMATIC Manager and load the existing STEP 7 project that contains the CPU 315-2DP station. If the project was previously only configured for MPI, the S7 program itself (OB1, FB, DB) does not need to change — the user program is unaware of the CP until you add a configured S7 connection in NetPro. For a basic Movicon polling setup using PG/OP communication, the program change is zero.

1. Open HW Config and double-click the rail.
2. Drag CP 343-1 Lean (6GK7 343-1CX10-0XE0) from the catalog into slot 4. If the catalog does not show the module, run Options → Install HW Updates and import the latest HSP.
3. Double-click the CP to open its properties. The General tab shows the order number and firmware; verify that it matches the physical label on the module.
4. Switch to the Properties → Ethernet Interface sub-dialog and click Properties… under IP Address Assignment.

Assigning a Static IP Address

Uncheck Set IP address using a different method and enter:

IP address:   192.168.1.10
Subnet mask:  255.255.255.0
Router:       (leave blank for a flat LAN)

If the SCADA host is the only client, any RFC1918 subnet is acceptable. Keep the CP and the SCADA host in the same subnet to avoid a router hop. After saving, compile and download the hardware configuration to the CPU. The CP will restart, perform a self-test, and the RUN LED turns solid green within 5–10 seconds. The BF (bus fault) LED should remain off; a steady red SF LED indicates a configuration mismatch (wrong CP inserted in slot 4, or wrong firmware in HW Config).

Enabling PG/OP and S7 Communication

In the CP properties dialog, open the Options tab. Verify that the following checkboxes are set:

• Set PG/OP interface — required for STEP 7 to attach to the CP for online functions.
• Enable S7 routing — only required if you have downstream stations, otherwise leave off.
• S7 communication via TCP/IP — must be on for Movicon and most third-party S7 clients.

For PG/OP communication, no connection object needs to be created in NetPro. The S7 protocol's PG port listens on TCP/102 by default and the SCADA driver is treated as a programming device from the CPU's perspective. For configured S7 connections (used by WinCC flexible, certain OPC servers, or redundant polling), right-click the CP and choose Insert New Connection → S7 Connection, then specify the partner as Unspecified with a local and partner TSAP. Movicon 11.5 does not require a configured connection in NetPro when using the standard S7 TCP/IP driver.

CP 343-1 Lean Operating Modes and LED Diagnostics

The CP has four front-panel LEDs. Their meaning is unambiguous in the CP 343-1 Lean manual:

A healthy state is RUN solid green, SF off, BF off. Once Movicon opens a connection, RUN remains solid; the BF LED is not lit just because no client is connected. A flashing BF means the link is up but no S7 partner is registered — this is the most common state immediately after download and is normal until the SCADA client starts polling.

Movicon 11.5 Driver Configuration

Open the Movicon project and navigate to Resources → Communication Drivers. The driver list shows the protocols available in the installed build. Add Siemens S7 TCP/IP (sometimes labelled S7 MPI/TCP Ethernet). Right-click the driver instance and open its properties. The relevant fields are:

Tag Database and Data Block Mapping

Movicon tags are addressed in the form DB<n>.<type><offset>. The most common data types and their STEP 7 counterparts are:

For a residential automation project it is common to centralize all SCADA-visible variables in two or three DBs — for instance DB100 for inputs (booleans from door contacts, window contacts, motion detectors), DB101 for outputs (relay states, dimmer levels), and DB200 for setpoints (room temperature target, lighting scenes, alarm arm/disarm). The DBs must be declared in STEP 7 with the symbol DB100, DB101, etc., and downloaded to the CPU. The CP 343-1 Lean does not require any symbol export or OPC XML file; the S7 driver reads raw byte offsets and trusts the DB layout.

Enable the attribute Optimized Block Access = OFF for any DB read by SCADA. Optimized access hides the byte layout and the driver cannot read symbolic names. With optimized access off, the DB is treated as a classic S7-300 data block and every byte has a stable offset.

Step-by-Step Commissioning Procedure

1. Power off the S7-300 rack, insert the CP 343-1 in slot 4, power on. Observe SF and BF — if SF is steady red, the CP firmware revision in HW Config does not match the physical module.
2. Connect an Ethernet patch cable from the CP to the switch. The BF LED should extinguish within 2 seconds of link-up. The SF LED should remain off.
3. Open STEP 7, go online with the CPU, and download the updated HW Config. The CP restarts and acquires its IP address (192.168.1.10 in the example).
4. From a Windows command prompt on the SCADA host, run ping 192.168.1.10. You should see replies with TTL=64 and round-trip times of 1–3 ms on a wired link.
5. Open Movicon, add the S7 TCP/IP driver, and enter the parameters from the table above. Save the project.
6. Click Driver Diagnostics in Movicon. The status indicator should transition from Connecting to Online within 3–5 seconds. The RX/TX byte counters will start incrementing as soon as the screen polls the first tag.
7. Add a numeric tag Test_Real with address DB100.DBR0 and a digital tag Test_Bool with address DB100.DBX4.0. Place both on a test screen and verify that bit changes in the PLC are visible on the HMI within one polling interval.

Troubleshooting Matrix

Performance, IP Cameras, and WiFi Considerations

The original CE6 panel hit a performance wall with both the SCADA runtime and the number of screens. A Surface 3 (or a modern Atom-based industrial panel) running Windows 10 and Movicon 11.5 will run the S7 driver with negligible CPU — typical poll of 200 tags at 500 ms uses about 1–2 percent of an i3 core. The bottleneck shifts from CPU to network: the CP 343-1 Lean supports 16 simultaneous S7 connections, of which the SCADA driver uses one. IP cameras should be placed on a separate VLAN or at minimum a separate SSID to prevent multicast traffic from saturating the automation network.

For wireless SCADA, deploy a 5 GHz WiFi network dedicated to the tablet. The CP 343-1 Lean is wired; the wireless hop is between the SCADA host and the switch. Roaming behavior of consumer WiFi adapters can cause momentary disconnects that the S7 driver interprets as connection lost. If the tablet moves between access points, set the driver's connection retry to 5 and the timeout to 5000 ms; this masks typical 802.11r transitions of 200–400 ms.

Security and CPU Access Protection

By default, the CPU 315-2DP allows any S7 partner on the network to read and write data blocks using the PG port. This is convenient for development but unacceptable on a permanent installation. Configure access protection in STEP 7 under CPU Properties → Protection:

• Level 1: No password — only suitable for closed commissioning networks.
• Level 2: Password for write access — recommended. SCADA can read everything; only STEP 7 with the password can write.
• Level 3: Password for read and write — Movicon may fail to read if it does not know the password. Only use if the SCADA driver supports password submission (most do not).

For Level 2, the Movicon S7 driver works without changes because all polling is read-only by default. The CP 343-1 Lean does not enforce CPU access protection on its own; the check is performed by the CPU. If the CP itself is secured (Options → Security in HW Config), the password is independent of the CPU password and applies to CP management web pages only.

Migrating to WinCC Flexible / TIA Portal WinCC

For projects that have outgrown Movicon, the next step within the Siemens ecosystem is WinCC Comfort/Advanced (TIA Portal) for PC-based visualization. The CP 343-1 Lean, STEP 7 project, and DB layout all carry over unchanged — only the HMI software changes. WinCC uses the same S7 protocol and the same rack/slot addressing, but it expects an HMI connection configured in the TIA Portal device → device network, with the CP 343-1 selected as the access point. The HMI tag database is generated from the PLC tag table, which is a significant maintenance improvement over manual Movicon tag entry.

Outside the Siemens ecosystem, open-source alternatives such as libnodave or S7.Net provide free S7-300/400 drivers for custom .NET or Python SCADA applications. The wire protocol is the same: ISO-on-TCP, port 102, rack 0, slot 2 for an S7-300.

Field-Notes Summary

Migrating a CPU 315-2DP installation from a CE6 panel on MPI to a modern Windows 10/11 SCADA host on Ethernet requires three deliberate decisions: the CP variant, the rack/slot configuration, and the SCADA driver slot value. Pick the CP 343-1 Lean for cost, configure rack 0 and slot 2 in the SCADA driver (not the CP's physical slot), and verify the link with ping and a single boolean tag before building the rest of the project. The legacy USB/MPI adapter (6ES7 972-0CB20-0XA0) and its Windows 10 driver problems disappear the moment Ethernet is in place.

Frequently Asked Questions