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SWO and variables reading

Pietsuro Botsutoshi
Note: This was originally posted on 27th February 2012 at http://forums.arm.com

Dear all,

I would like to create a SWV application, and my question is the following: how many variables can I read via SWO communication?

I mean, without considering the overflow packet that could be sent in case of huge information traffic, is there a physical limit regarding this topic?

If I've understood weel, DWT_COMPx registers, with x={1, .., 4} is used in order to store the variable address that I would like to monitor, and DWT_MASKx are also used in order to raise a valid new SWO packet.

Does this mean that it's possible to check only for four variables, or should I set the mask register in order to detect ranges of variables?
With the latter case I could be able to monitor a very large number of items.

Am I wrong or is this the right approach?

Thank you very much!
Parents
  • Note: This was originally posted on 26th March 2012 at http://forums.arm.com

    Ciao Joseph,

    great reply, thank you again.

    And now just a hint request...anyhow things are getting more clear in my mind now, so thank you very much.

    I'd like to monitor several variables with SWO, but for more than two of them I get overflow packets.

    Ok, I know this is a "physical" protocol limit, but can you please list a collection of tips or must-do-do in order to achieve best possible performances for this type of task?

    For instance, is it better to use a single DWT_COMP register with DWT_MASK greater than 0 or to assign to every variable to monitor each specific DWT_COMP component?
    Any suggestion regarding prescaling settings?

    Thanks for the cooperation!
Reply
  • Note: This was originally posted on 26th March 2012 at http://forums.arm.com

    Ciao Joseph,

    great reply, thank you again.

    And now just a hint request...anyhow things are getting more clear in my mind now, so thank you very much.

    I'd like to monitor several variables with SWO, but for more than two of them I get overflow packets.

    Ok, I know this is a "physical" protocol limit, but can you please list a collection of tips or must-do-do in order to achieve best possible performances for this type of task?

    For instance, is it better to use a single DWT_COMP register with DWT_MASK greater than 0 or to assign to every variable to monitor each specific DWT_COMP component?
    Any suggestion regarding prescaling settings?

    Thanks for the cooperation!
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