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CCS/MSP432P401R: Cycle Count

Kenneth Faller
Prodigy 70 points

Part Number: MSP432P401R

Tool/software: Code Composer Studio

I'm I'm trying to find out how many cycles a loop takes. I'm using the cycle count feature in the breakpoint window of the ccs debugger. If I step through the block of code, I get a lot more cycles then if I were to execute the whole loop. For example, if I step through, I calculate that one interation of the loop is 2 cycles. So, assuming that if I execute the loop 1000 times, I should only get about 2000 cycles. However if I run the whole loop, I end up with something like 12,000 cycles. What am I doing wrong?

Thanks,

John 

  • 0
    TI__Guru 58026 points

    Hello Kenneth,

       I will need to look into this some more, but I believe that I found a similar discussion here (

    https://e2e.ti.com/support/development_tools/code_composer_studio/f/81/p/546281/1995588

    ).

    I do not exactly follow your description and example.  Are you saying that when you stepped through the code you end up with 12K cycles or if you let it free-run.  Also, are you resetting the counter?

    Thanks,
    Chris

  • 0 in reply to Chris Sterzik
    Prodigy 70 points

    Thank you for your response Chris. I made a video to try to clarify what is happening. In this example, when I step through, I takes 3 cycles to execute the instructions in the loop (including the branch) and the loop is iterating 30k times. I would expect ~90k cycles if I did the whole loop. However, as you see at the end, I get ~360k cycles.

    https://youtu.be/Cg_v4gXmwbg

    John

  • 0 in reply to Kenneth Faller
    TI__Guru**** 173310 points
    John,

    Which version of CCS are you using? I see in the video that the main source file is written in assembly. Is that the only source in the project or is it a combination of C and assembly?

    Would you be willing to send us your project so we can reproduce the issue here and look into it further? If so, please zip up and attach your project here. Thanks.
  • 0 in reply to AartiG
    Prodigy 70 points

    I'm using CCS v7.2.0.00013. A C file is calling the assembly file.  Here is the file.

    Thanks,

    John

    0211.code.zip

  • 0 in reply to Kenneth Faller
    TI__Guru**** 173310 points

    John,

    I am not able to reproduce your results. I ran your project on CCS 7.2 and get a cycle count of ~120k cycles, so 4 cycles for each run through the loop. I am attaching a video of my result below.

    I'm not sure why you are seeing ~360k cycles. I ran the code on a MSP432 Launchpad, is that what you are using as well?

  • 0 in reply to AartiG
    Prodigy 70 points

    Thanks for the reply. Yes, I'm using the MSP432 LaunchPad (MSP-EXP432P401R rev 1.0). Is the problem specific to this revision?

    One other question about the video Artie, is the branch 2 cycles? Because you only have 3 instructions in the loop. Should it be ~90k cycles, not ~120k?

    Thanks,

    John

  • 0 in reply to Kenneth Faller
    TI__Guru 58026 points

    John,

       We do recommend that you move to the latest platform (revision 2.x of the launchpad and revision C or greater silicon).

    Regards,

    Chris

  • 0 in reply to Chris Sterzik
    Prodigy 70 points
    Chris,

    So it isn't working b/c of the Onboard XDS110?

    Thanks,

    John
  • 0 in reply to Kenneth Faller
    TI__Guru**** 173310 points

    Kenneth Faller said:
    One other question about the video Artie, is the branch 2 cycles?

    Yes, it seems so according to this ARM reference page on Cortex M instructions and cycle count.

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