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ULINK: Could Not Stop Cortex-M Device

Information in this knowledgebase article applies to:

  • MDK V4 All versions
  • MDK V5 All versions


When I try to connect my ULINK adapter to my target board, I get the following message:

Could not stop Cortex-M device!
Please check the JTAG cable

What can cause the error?


This error is an indication that the ULINK adapter cannot control the Cortex-M device. There are many possible reasons for this. Note: This is not an exhaustive list:

  • The target device is not powered.
  • The ULINK ribbon cable is too long or broken.
  • The Max Clock setting is wrong for this device. Reducing the clock setting often helps. See ULINK JTAG/SW Adapter
  • The JTAG or SWD signals are missing or not connected properly. See Target Connectors.
  • You may need to modify the Connect and Reset Options if you are using a custom Cortex-M implementation.
  • To use on-chip flash, in some NXP Cortex-M devices, µVision requires a special signature creator, called ElfDwT, as a User command, Post-build. In this case, failing to call ElfDwT.exe causes user code placed in internal flash to be considered invalid. For more information on how to use ElfDwT, see the knowledgebase article below or refer to Options for Target => User tab, in MCB1800/4300 example's on-chip flash targets.

If error message appears at beginning of debug mode, try disabling Run to main in Options for Target => Debug tab. This may allow user to step through initial startup or boot code to view more debug information, before the error message.



Last Reviewed: Tuesday, April 4, 2017

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