Siemens S7-300/400 Ethernet Connection Guide

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The Siemens S7-300 PLCs support CP-343-1 Ethernet modules, and S7-400 PLCs support CP-443-1 Ethernet modules. Software programs such as Fernhill SCADA can monitor and control S7-300/400 PLCs via Ethernet using a either a CP-343-1 module, or a CP-443-1 module.

S7-300 and S7-400 PLCs support a number of open connections:

Communication Overview

A typical communication scenario is shown in this diagram:

Diagram showing a Siemens S7-300 PLC with a CP343-1 communication module

To establish communications between Fernhill SCADA and a Siemens S7-300 or S7-400 PLC you need to configure:

Setting up an Ethernet CP Module on a Siemens S7-300/400 PLC

1. Open Simatic Manager and load a project with only a CPU configured:

Simatic manager with a 312IFM CPU configured

Note: This project is using a CPU 312 IFM, but any CPU would be suitable.

2. Select the simatic station, then double click Hardware. The HW Config tool opens:

Simatic manager hardware configuration tool opened

Note: On the right side of the HW Config tool is the Hardware Catalog. If, for any reason, the Hardware Catalog is not visible, you can show it by selecting View, followed by Hardware Catalog from the menu.

3. In the Hardware Catalog Windows, expand the CP-300 tree until you locate the communication module you are using. In this example we are using a 6GK7 343-1EX11-0XE0:

Simatic manager hardware catalog locating communication module

Note: Some CP modules have different version numbers. Be sure to select the correct version of module you are using.

4. Drag the selected module to slot 4 in the rack:

Simatic manager adding the communication module to the rack

5. Right click on the newly added CP 343-1 module and select Object Properties. The Properties dialog opens:

Simatic manager edit communication module properties

6. Click the Properties button. The Ethernet Interface dialog opens:

Simatic manager edit ethernet properties

7. Enter a suitable IP address and Subnet mask. Click the New... button to create a new Subnet. The Subnet Properties dialog opens:

Simatic manager create new subnet

8. For this walkthrough, the Subnet properties can all be left at their defaults. Complete the configuration of the CP 343-1 using these steps:

  1. Click OK on the Subnet Properties dialog to create the new subnet.
  2. Click OK on the Ethernet Interface dialog to finish configuring the Ethernet interface.
  3. Click OK on the Properties dialog to finish configuring the properties of the CP 343-1.
  4. On the HW Config window select Station, followed by Save and Compile.
  5. Close the HW Config window.

When complete Simatic Manager should now show the configured CP 343-1 module:

Simatic Manager showing the configured CP 343-1 module

9. On Simatic Manager right click on the simatic station (in this case SIMATIC 300(1)), and select PLC, followed by Download. Follow the sequence of dialogs to download the new configuration to the PLC.

Note: At this stage the CP 343-1 module should be configured with its IP address. You can test this by pinging the module.

10. On Simatic Manager right click on the PLC (in this case CPU 312 IFM) and select PLC, followed by Copy RAM to ROM... The Copy RAM to ROM dialog opens:

Simatic Manager dialog showing warning about copying RAM to ROM

11. Click Yes to start the copying procedure. If the PLC is in RUN mode, a dialog will appear asking you to change the PLC to STOP mode. Click Yes on this dialog to put the PLC in STOP mode. When the copy process is complete a confirmation dialog opens:

Simatic Manager dialog showing copy RAM to ROM complete

Note: When the copy process is complete the PLC will be in STOP mode.

12. The PLC will now be in STOP mode. Power cycle the PLC and CP module. When the PLC and CP module have restarted, ping the CP module to confirm it has cold started with its configured IP address.

Configuring Fernhill SCADA

There are two options for configuring Ethernet communications from Fernhill SCADA to a Siemens S7 PLC:

Further Information

Siemens S7 TCP Autodetect Wizard

For how to automatically configure Fernhill SCADA to communicate with Siemens S7 PLCs using Ethernet.

Siemens S7 Ethernet channel

For information about the Siemens S7 Ethernet channel tag.

Siemens S7 TCP/IP PLC

For information about the Siemens S7 TCP/IP PLC tag.

Siemens S7 Driver

For information about the Siemens S7 Driver.


For the meaning of terms used in Fernhill SCADA.