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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
  • Arm Employee Badge
    Note: This was originally posted on 28th March 2012 at http://forums.arm.com

    Hi,

    In general you won't consider the first byte of sync packet as header.
    Before trace stream is synchronized you won't know where the start is,
    so you look for continuous of 47 bits 0 an then a 1 to tell where the trace start.

    I am out of office at the moment and will be back next week.
    If it is not urgent I get back to this when I am back.

    regards,
    Joseph
Reply
  • Arm Employee Badge
    Note: This was originally posted on 28th March 2012 at http://forums.arm.com

    Hi,

    In general you won't consider the first byte of sync packet as header.
    Before trace stream is synchronized you won't know where the start is,
    so you look for continuous of 47 bits 0 an then a 1 to tell where the trace start.

    I am out of office at the moment and will be back next week.
    If it is not urgent I get back to this when I am back.

    regards,
    Joseph
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