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TMS320F280049: Race condition when EPWM shadow to active load and action qualifier both at TBCTR = PRD

Sheldon He
Expert 8585 points
Part Number: TMS320F280049

Hi expert,

My customer would like to know what will happen in below PWM configurations since shadow load and action qualifier happens at the same time.

1. PWM counter in up- down mode, CMPA is shadow loaded with TBPRD value

2. AQ settings: CAU to clear and CAD to set

3. Shadow to active loading point: TBCTR = ZERO or TBPRD

Presume the PWM output is originally in high state during counting up, will it be cleared at the first time TBCTR goes to TBPRD? Why?

Thanks

Sheldon

  • 0
    TI__Mastermind 24095 points

    Sheldon,

    It is recommended to avoid this conflict of using the same value (in this case TBPRD) as reload event and compare match to set an action.

    Below are the notes in the TRM:  18.3.4.5 Waveforms for Common Configurations

    Use up-down-count mode to generate a symmetric PWM:
    • If you load CMPA/CMPB on zero, then use CMPA/CMPB values greater
    than or equal to 1.
    • If you load CMPA/CMPB on period, then use CMPA/CMPB values less than
    or equal to TBPRD-1.