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µVISION DEBUGGER: Using a Segger J-Link Script File During Debugging

Information in this knowledgebase article applies to:

  • MDK v4.0 and later


I cannot establish a debug or trace connection using Keil MDK and a Segger J-Link (or a Segger J-Trace). I have verified this works using third-party software tools. Are there additional settings I can set in a debug script?


Since Segger manufactures the J-Link adaptor, they provide a J-Link dll to Keil. To use this dll in the Keil µVision IDE: in the Project -> Options For Target -> Debug tab, on the right-hand side, click the Settings button to open the Cortex JLink/Jtrace Target Driver Setup dialog. In this dialog, configure the Debug and Flash Download settings settings for the Segger J-Link or J-Trace.

Instead of just using a debug script initialisation file (.ini file) on the Debug tab, use these methods provided by Segger for additional configuration options.

  • J-Link Commander - a command line interface for inputting J-Link Commands.
  • J-Link Control Panel - the J-Link dll called in the background by the Keil µVision Debugger. Use it to monitor debug status, and configure some J-Link features.
  • J-Link Debug Script files - for additional control of reset, trace configuration, delays, debug commands, etc.
Debug Script Types

Two types of Segger debug script files are:

  • *.JLinkScript file: J-Link Script File in plain text format
  • *.Pex File: pre-compiled, non-modifiable file, i.e., it is not plain text or human-readable. Contact Segger if the project needs a modified version of the script file.
  • Some CMSIS-PACK examples come with JLinkScript files. Using Windows Explorer, search the pack directory of your device family (typically in C:\Keil_v5\Arm\pack) for ext:JLinkScript.
  • Segger provides examples projects that include J-Link script files. See their debug probe wiki page for those examples.
    • Download and unzip an example project to view the J-Link script file.
  • Make a custom J-Link script file. See their sample J-Link script wiki page.


When starting the Keil µVision Debugger, the J-Link dll always tries to use the JLinkSettings.JLinkScript in the project directory (if present). So to use a .JLinkScript file in Keil MDK5:

  1. Using Windows Explorer, open the folder where the µVision project file (*.uvprojx) is.
  2. Copy the *.JLinkScript into this folder. Rename it JLinkSettings.JLinkScript.
  3. In the µVision IDE, select Debug -> Start/Stop Debug Session and verify the J-Link script ran.
  4. See more in the Segger wiki page for Keil MDK.

Another method for including a Segger J-Link script file within a Keil MDK project:

  1. In the Keil IDE, on the Project -> Options For Target -> Debug tab, click the click the Settings button to open the Cortex JLink/Jtrace Target Driver Setup dialog - this activates the J-Link dll.
  2. With the J-Link driver in use, a j-link-control-panel-icon J-Link system tray icon - a green box with a white "J" - appears in the Microsoft Windows task bar notification area.
  3. Click on the J-Link Icon to open the Segger J-Link Control Panel.
  4. There, switch to Settings tab.
  5. In the third field in the dialog - the Script file field - click the button. Browse to the J-link script file. Press Open to close this dialog.
  6. For *.pex file types: change the file filter from J-Link script files (*.Jlinkscript) to All Files (*.*) then press Open.
  7. Close the Segger J-Link Control panel this saves the reference J-link Script file settings in the JLinkSettings.ini in the project folder.
  8. In the µVision IDE, select Debug -> Start/Stop Debug Session and verify the J-Link script ran.
  9. More information in their J-Link script file wiki page.

Additional Notes

  • Debug Configuration (dbgconf) files will not work with a J-Link or J-Trace. Use a Segger debug script instead.
  • In some cases, the debug sequence in the J-Link script file is only implemented for JTAG. In such cases, JTAG mode must also be set in the Cortex JLink/Jtrace Target Driver Setup dialog (in the Project -> Options For Target -> Debug tab).
  • Every time the J-Link dll connects to the J-Link debug adaptor, it automatically generates a JLinkSettings.ini file in the project directory. Changing a value in the Cortex JLink/Jtrace Target Driver Setup dialog updates a corresponding field in the JLinkSettings.ini file.


More Information

  • Read more about using a J-link with Keil MDK on Segger's webpage.
  • To read about Segger J-Link commands in the J-Link / J-Trace User Guide, download the J-Link Manual here.

See Also

Last Reviewed: Monday, January 11, 2021

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