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TMS320F2800157: Inquiry on Occasional Loss of CBD Event in EPWM

Lawrence Wang
Prodigy 580 points
Part Number: TMS320F2800157

Tool/software:

Hi experts,

My customer have encountered an issue with the EPWM module and would like your guidance.

Issue Description:

  • CMPB Value: 54-408
  • Period Value: 454
  • Mode: Up-Down Count Mode
  • Expected Behavior: The CBD (Compare B Down) event triggers the output to pull low.
  • Observed Behavior: Occasionally, the CBD event or the pull-low action is missed.

Question:
Under what conditions could the Action Qualifier (AQ) occasionally fail to trigger the CBD event?

  • +1
    TI__Mastermind 25696 points

    Hi Lawrence,

    There are a few conditions that AQ can fail to trigger on a CBD event.

    1. Phase shift is enabled causing the TBCTR to 'skip' over the CBD event by setting a value to TBPHS that is greater than the CBD value.

    2. CMPB value is set to a value greater than TBPRD.

    3. CMPB value was not loaded due to some misconfiguration or missed load event.

    4. Some abnormal behavior causing the PWMs to stop counting such as a SYSRSn. This would cause default values for the PWM.

    5. Higher priority AQ event occurs such as software force, T1/T2 event.

    Best,

    Ryan Ma