Loading Application Code — Login and Starting the PLC

In order to download the source code of your application to the controller, you must log in to the controller with application. If there are several applications in the project, then you must switch explicitly to the correct application first.

When you download an application to the controller, CODESYS performs the following checks:

The list of applications on the controller is compared with the applications available in the project. If they do not match, then you are prompted to download the application that is not on the controller yet or delete existing applications.

For “externally implemented” blocks in the application to be downloaded, CODESYS checks whether these are available on the controller. If they are not available, then the message “unresolved reference(s)” is printed to a dialog prompt and to the messages view. Then CODESYS compares the parameters (variables) of the blocks in the application to be downloaded and the parameters of the same-named blocks in the application that exists on the controller (signature check). If there are any discrepancies, then the message “invalid signature(s)” is printed to a dialog prompt and to the messages view.

If the “Download Application Info” check box is selected in the application properties, then additional information about the application contents are downloaded to the PLC.

if multiple applications exist for the same device, then please note the I/O Mapping dialog box contains the application definition for the I/O mapping of the device that is used.

See also

Transferring applications and starting programs

Requirement: The application contains no errors and the communication settings of the controller are correct. The application does not exist yet on the controller:

  1. Select the required application in the device tree. Skip to Step 3 if you have only one application.

  2. Click Set Active Application.

    ⇒

    The application name appears in bold typeface.

  3. Click Online ‣ Login.

    ⇒

    A dialog box prompts you whether the application should be created on the controller.

  4. Click Yes to confirm.

    ⇒

    The application is downloaded to the controller.

  5. Click Debug ‣ Start or press F5.

    ⇒

    The application is running on the controller.