How to Change the MPI Node Address For a Siemens S7-300 PLC

I have seven Siemens S7-300 PLCs connected together using the MPI (Multi Point Interface) interface. The Siemens MPI protocol is used by Siemens PLCs to communicate with external devices. I want to rename each of the seven PLCs. Here are the steps to accomplish that task.

First, connect your MPI cable to the first PLC. I will be connecting my laptop to each PLC individually. Power up the PLC and open Simatic Manager. The "New Project" Wizard window will open. Just click Cancel to close the window. Now click the Accessible Nodes icon on the toolbar. A window will open showing the identification of the PLC you are connected to. My window is showing MPI = 2 (directly). Make a note of this address and close the window.

Next we need to download a hardware configuration to the PLC. This is where we will rename the PLC node address. There are probably a couple of different ways to do this – following is how I accomplish this. All seven of my PLCs are the same model; Therefore, I am using the same hardware configuration. For the obvious reasons, I want to give each a different MPI node address. I have a project file that contains all seven of my PLC programs and one hardware configuration file. I open the one hardware configuration file, and then double click Hardware in the right hand window. This will open the HW Configuration window. In this window you should see your PLC with its MPI address given.

Remember when we clicked the Accessible Nodes icon and saw MPI = 2 (directly)? My Hardware Configuration Window is showing a MPI address of 7. Place your mouse cursor on the 7 and double click. Your CPU Properties window will open. It should open to the General tab. Look down and you will see Interface Type MPI with an address of 7. Click Properties and the MPI interface Properties window will open. Using the pull down menu, choose your MPI node address and make sure the MPI (1) 187.5kbps is highlighted and click OK. You are now back on the CPU Properties window where you will see your address has changed. Click OK and you will go back to the Hard Ware window where you can verify your MPI node address has changed.

You will now click the Save and Compile icon and then click the download icon. The Select Target Module window will open. Click OK and the Select Node Address window will open. Here you will see the MPI node address you assigned earlier. You will need to click the View button right below this. You will see the current node address appear, this should be the same as what you saw earlier when you clicked the Accessible Nodes icon. Simply click on this number and you will see it appear in the MPI address slot under the Enter connection to target station. Click OK and the Download to Module window will open. Click OK and the Stop Target Modules window will open. Click OK and the "Do you want to start the module?" Window will open. Click Yes.

Now go back to the SIMATIC Manager window and click the accessible nodes icon. You will see your new MPI node address. You can see this same article with pictures at http://www.morerobototics.com .

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