[SOLVED] SWD speed reduced for stability

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  • [SOLVED] SWD speed reduced for stability

    Hi,

    I am trying to use a higher speed on my debugger (JLink PRO) than the default 4000 kHz.

    Using JLink commander (JLink.exe) I try to set the speed to 25MHz, but get this message:

    SWD speed too high. Reduced from 25000 kHz to 16875 kHz for stability

    My cables are quite long (about 50cm in total), and I suspect that this is skewing the signals and thereby limiting my speed.
    Am I correct in my assumptions?

    I will try to shorten the cable once I get hold of new plugs, but also wanted to double check here if there is something else that could causing problems.
    Ideally I want to use the highest speed possible (100MHz).

    I am interfacing an EZR32WG230 microcontroller from Silicon Labs.

    Bauck

  • Hello Bauck,

    Thank you for your inquiry.
    Whenever SWD communication fails due to bad signals J-Link will automatically reduce the speed and try to connect again.
    Does connect work with the slower interface speeds than 16 MHz?

    Bauck wrote:

    Ideally I want to use the highest speed possible (100MHz).
    This will most likely not be possible as the 100 MHz needs to come from somewhere on the target device as well. The EZR32WG230 runs only at maximum 48 MHz CPU clock.
    So it is highly unlikely that this core will have a peripheral clock that can run faster than that.
    For more information about the maximum supported interface speed we suggest contacting Silicon Labs in that regard.
    Our guess is that the 16 MHz are already the limit of the chip. Which speeds can you achieve with the cables shipped with J-Link?

    Best regards,
    Nino
    Please read the forum rules before posting.

    Keep in mind, this is *not* a support forum.
    Our engineers will try to answer your questions between their projects if possible but this can be delayed by longer periods of time.
    Should you be entitled to support you can contact us via our support system: segger.com/ticket/
    Or you can contact us via e-mail.

  • Hi Nino,

    Thank you for your quick answer.

    I tested with a tag connect cable instead and I am now able to set the speed to 25 MHz. (BTW the speed I wanted to use was 50 MHz, not 100 MHz, I just mixed up with the max SWO speed).

    I does look like the maximum speed is around 26 MHz which corresponds with the frequency of the external crystal in the design.

    Thank you again,
    Bauck

  • Hello Bauck,

    Great to hear that you are up and running again.
    We consider this thread as solved now.

    Best regards,
    Nino
    Please read the forum rules before posting.

    Keep in mind, this is *not* a support forum.
    Our engineers will try to answer your questions between their projects if possible but this can be delayed by longer periods of time.
    Should you be entitled to support you can contact us via our support system: segger.com/ticket/
    Or you can contact us via e-mail.