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SWO and variables reading

Offline Pietsuro Botsutoshi over 9 years ago

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!

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Offline Joseph Yiu over 9 years ago

Note: This was originally posted on 26th March 2012 at http://forums.arm.com

Hi,

I forgot to mention that function 0xC to 0xF are available from Cortex-M3 r2p0. The chip that you are using could be from Cortex-M3 r1p1, which might not have the capability to generate data trace on data write only. For r1p1 or earlier versions of Cortex-M3, you can only use function 0x0 to 0xB.

You can find the r2p0 TRM from here : http://infocenter.arm.com/help/topic/com.arm.doc.ddi0337g/DDI0337G_cortex_m3_r2p0_trm.pdf

regards,
Joseph
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Offline Joseph Yiu over 9 years ago

Note: This was originally posted on 26th March 2012 at http://forums.arm.com

Hi,

I forgot to mention that function 0xC to 0xF are available from Cortex-M3 r2p0. The chip that you are using could be from Cortex-M3 r1p1, which might not have the capability to generate data trace on data write only. For r1p1 or earlier versions of Cortex-M3, you can only use function 0x0 to 0xB.

You can find the r2p0 TRM from here : http://infocenter.arm.com/help/topic/com.arm.doc.ddi0337g/DDI0337G_cortex_m3_r2p0_trm.pdf

regards,
Joseph
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