General Articles

Going online – PLC Software Education Logic

There are three possible scenarios when going online. The one will be that you have the matching project file so that matching project file means that the file that is available on your computer matches the project that is loaded in the controller. The data itself is not going to be compared, but the logic configuration settings have to match.

The second scenario will be that you have the project file, but it doesn’t match the one that is in the controller, so there is something different between the file on your hard drive and the one that is loaded in the controller. This is a common issue when you have multiple computers editing the same controller.

The third scenario is when you do not have the project that is in the controller. So, this could be a strange controller that you have never connected to before.

Read more about it here:

Establishing connection

Establishing online communication with the processor will enable you to execute projects, monitor and troubleshoot projects, and edit and test projects. Before you can go online, you must complete some required steps. You must prepare your project to communicate with the processor. Also, download a project to the processor.

Before the communication can occur, you must make sure that your processor is properly connected to your computer and that power is applied to the processor’s rack. Then you have to confirm in the software that the driver is configured and running by observing configure drivers dialog box.

You need to make sure you are very careful with any changes you make while you are online. You will be affecting a live system if you are working, and it can cause damage to equipment or you could put personnel in danger if you are not careful. You can write the code and test it then go online and make the same changes. Read more here.

When project doesn’t match the controller

The first thing you should do is to go to the communications menu, and from the communications menu the option that you want to use is “Who Active”. Ideally, forget about all other options, those are the options that are going to give you trouble. If you stick to “Who Active” you should be okay.

In the windows that open up, the goal is to find your controller. When you look at the Ethernet driver, click on the plus and select the controller. What you are doing here is telling it to leave your computer using the Ethernet IP driver. In some systems that right there could actually be your controller, and when you select it, the buttons at the right would be available to click on. In the case when you have separate Ethernet module, you need to select the controller. Then you will have the options to go online, download, and upload.

When you selected the controller and clicked on “Go Online”, it is going to look at the project loaded in the controller and it is going to compare that to the file you have opened. You will have an upload option that will read the project in the controller and then open it up.

When you have the matching project

Now you are online with the controller, you will notice that the controller is currently in a remote program mode. Also, you can see the keys in the remote position, and it says at the very bottom that upload is complete without errors or warnings.

Next, you should go to file and save it, the window will come out to ask you if you want to do the upload that will save any tag values that have changed since you first got online, and you should click yes. Your file on your hard drive should match the one that is in the controller.

If you go back to the communication menu and set it offline, and then when you go to communications and “Who Active”, you can see it remembered where the controller was. So now, when you tell it to do online, the file on your hard drive should match the one that is in the controller and it takes you online immediately.

When you do not have the project file

Try deleting your project and also if you have a copy of it. Then, when you go to communications and “Who Active”, it remembers where your controller was, but remember what that path is. It is: you are leaving your computer, you are going out your Ethernet connection, and you’ll have the IP address of the remote chassis, you are going through that Ethernet module to the backplane and then in the slot where the controller is located.

When you attempt to go online, this time the message that you will get is going to be a little bit different. It will say that it couldn’t find the project. So, you can select a new or existing project file. What they mean by that is when you hit select file, it is entirely possible that you have the project, but that project is in some other folder. So, you can browse where that file is and it will compare and see if it matches, or you can enter in the name of a new file.


There are shortcut methods for uploading and downloading PLC projects.  If you go back offline, you will notice under the communication menu there is a go online option. You should be very careful about using these options. These options rely on the path settings that identify which controller is going online. So, when you check those settings you can use the shortcuts, but experienced people recommend avoiding that.

“Who Active” menu is the best way to go. If there were any sort of communication error, you would be able to see it. If you disconnect the Ethernet cable you will see a communication error pop up that you would not see with the other drivers.

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