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ULINK: Trace port selection using ULINKpro

Information in this knowledgebase article applies to:

  • Keil MDK
  • ULINKpro, ULINKpro-D Debug Adapter


I am using ULINKpro and enabled the Trace in Options for Target - Debug - Settings - Trace

Serial Wire Output - UART/NRZ is selected as Trace port, as shown in the screenshot.

However, when I try starting a Debug Session, the error Selected Trace Port is not supported is shown. 

Which Trace Port is supported by ULINKpro?


  • ETM Instruction Trace
  • After enabling ETM trace, in the Trace Port droplist, Sync Trace Port with 4-bit Data needs to be selected. Sync Trace Port with 1-bit Data or Sync Trace Port with 2-bit Data mode cannot provide enough data bandwidth for ETM trace data, since fewer trace port pins are used in these cases.

    Note, ETM trace is supported by ULINKpro, but is not supported by ULINK2 or ULINKplus.

  • ITM/DWT Trace
  • When using ULINKpro, Serial Wire Output - Manchester is typically selected, which provides better tolerance of difference between trace clock setting and system core clock, which results in better-synchronized trace data.

    Sync Trace Port with x-bit Data modes can also be selected when using ULINKpro, if 4/2/1 pins trace port is available and properly configured.

    Note, Serial Wire Output - UART/NRZ mode is not supported by ULINKpro. That's the reason why the error above happens.

    When using ULINK2, the only supported option Serial Wire Output - UART/NRZ is selected by default. This mode requires setting the trace clock identical to the system core clock, in order to get synchronized trace data.

    Note that Sync Trace Port with x-bit Data and Serial Wire Output - Manchester modes are not supported by ULINK2.



Last Reviewed: Tuesday, November 3, 2020

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