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CMSIS: ISR_FIFO access failed in RTX RTOS window

Information in this knowledgebase article applies to:

  • MDK-ARM V5.23
  • Keil::MDK-Middleware V7.4.0
  • ARM::CMSIS V5.0.1


During migrating my project to RTOS2 and RTX5 I recognize that after stepping over osKernelInitialize() strange messages appear at the RTX_RTOS window:

RTX RTOS Object: Expression: os_Config.isr_queue_data
RTX RTOS Object: E302: Access failed = read 'ISR_FIFO': (@0x20001000) - acccess failed


At the file RTX5.scvd the ISR queue member offsets were invalid


  • either replace the attached file RTX5.scvd at C:\Keil_V5\ARM\PACK\ARM\CMSIS\5.0.1\CMSIS\RTOS2\RTX\
  • or install a newer version of the ARM::CMSIS pack with the PackInstaller



Request the files attached to this knowledgebase article.

Last Reviewed: Tuesday, March 7, 2017

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