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MSP430F5438A: Timer stops in LPM3 when powered from ACLK

Jürgen Wissenwasser
Intellectual 490 points

Part Number: MSP430F5438A
Other Parts Discussed in Thread: MSP-FET

Hi!

I have an application where I need a PWM output while the system is in LPM3. Thanks to a low frequency requirement I use ACLK=XT1 (which is already in use for RTC) as clock source.

When I run the pwm via a timer (in this case TA1) with ACLK as clock source the timer stops operating UNLESS I set SMCLKOFF=0 - this is weird as SMCLK is NOT the timer clock source and there is also no hint in the errata.

  • 0
    TI__Guru* 84961 points
    Hi Jurgen,

    That is indeed a strange issue. Can you please share a code snippet showing your code for configuring the clock, your code for configuring the timer, and your code where you go to LPM3? This will help us to debug your issue and potentially make it possible for us to reproduce the behavior.

    Regards,
    Katie
  • 0 in reply to Katie Pier
    TI__Guru* 84961 points
    Hi Jurgen,

    Is there any update that you can provide for the questions above or any more we can do to help? Or were you able to resolve the issue?

    Regards,
    Katie
  • 0 in reply to Katie Pier
    Intellectual 490 points

    I am not sure but I think there are multiple issues:

    The latest IAR Workbench sometimes does not correctly operate the emulator - e.g. the clocks are configured to run when the CPU is halted but this does not always work. Also, I use the latest TI MSP-FETFlash Emulation Tool and sometimes IAR WB crashes during debugging. However: It is not my job to be a beta-tester of whatever tool I use.

    Something else regarding MSP: Which idiot had the idea for a hand-made noisy step-down-converter in the debugger? This is pure bullshit and causes noise, noise and even more noise.

  • 0 in reply to Jürgen Wissenwasser
    TI__Guru* 84961 points
    Hi Jurgen,

    Thanks for responding, and I understand your frustration. To try to better understand your issue so that we can try to reproduce it, could you help us to get a little more information about your problem:
    1. Do you only see the issue in debug mode (are you still seeing the issue of timer stopping, but only in debug mode or when you halt the emulator)? Can you share your debug clock settings found (while debugging) under Emulator > Advanced > Clock Control?
    2. Can you share a simple piece of code that exhibits the issue so we can reproduce the issue on one of our boards?
    3. Can you share the basic steps it takes to reproduce the issue, and what the failing case looks like (what behavior we should observe)?
    4. Can you confirm the IAR version that you are using (under Help > Product Info, does it says IAR Embedded Workbench for MSP430 IDE version 7.10? )

    For the noise issue that you mention you are having, I would recommend to try using an external power supply to power your device. For debugging in this configuration, you will need to change the connection from Vcc on your board being connected to pin 2 of the MSP-FET (for powering the board from the tool) to pin 4 (for external power). This allows the MSP-FET to sense the voltage being used externally and adjust the signal levels on the JTAG/SBW communication lines accordingly.

    Regards,
    Katie

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