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µVISION DEBUGGER: "Internal DLL Error" During Flash Programming

Information in this knowledgebase article applies to:

  • MDK-ARM v5.23
  • ULINKpro debug adapter


I'm using ULINKpro on an existing project created by previous MDK v5.x. After upgrading MDK to v5.23, during flash programming I always get the following errors:

Erase Done.
Programming Failed!
Internal DLL Error
Error: Flash Download failed - "Cortex-M3"

I didn't modify any project or debug settings of this project. How can I resolve this issue?


Such an issue happens when using ULINKpro in MDK v5.23 in the following cases:

  • Application images >= 8K
  • Flash program page size >= 4K 
  • Device Memory Access Port has an auto-address increment page of 4K or larger (mostly on Cortex-M3/M4 based CPUs)


This issue has been fixed in MDK newer than v5.23.

MDK v5.23 users may download the attached zip file containing the updated DLLs and replace them into:
Where [installation_path] is wherever you installed the MDK tools. The default [installation_path] is: C:\Keil_V5.


Request the files attached to this knowledgebase article.

Last Reviewed: Friday, February 24, 2017

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