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TMS320F280049C: Global Load / DBRED + DBFED / CMPB questions

Rio Chan
Genius 14795 points
Part Number: TMS320F280049C

Champs:

My customer is asking this:

   Q1. on the 049 TRM , Section 18.7 / page 1933, there is a Global Load support section.

         The question is: When we active the  Global load on the Zero point, are the value of (DBRED and DBFED) being updated in the next phase?

         Plz confirm.

   Q2. If we active the Global Load, and use the CMPA / CMPB to do the Phase Shift, And the update frequency is equal to the PS freq, do we have any limitation? And will this generate the "unexpected wave"?

PLz confirm.

Thanks.

BR Rio

  • 0
    TI__Mastermind 25716 points
    Rio Chan said:

             The question is: When we active the  Global load on the Zero point, are the value of (DBRED and DBFED) being updated in the next phase?

    If you're loading on ZRO point, DBRED and DBFED values should be updated accordingly. This note mentions that if if the DBRED/DEBFED is loaded with a new shadow value while DB counters are counting then you'll see the delay in the next PWM edge. Since you're loading at a ZRO point, i don't believe you'll run into this issue. This note applies to when trying to load during the period DBRED/DBFED is being applied on currently.

    Rio Chan said:

       Q2. If we active the Global Load, and use the CMPA / CMPB to do the Phase Shift, And the update frequency is equal to the PS freq, do we have any limitation? And will this generate the "unexpected wave"?

    If you're using CMPA/CMPB to do phase shift, are the slaves synchronized to a master PWM? Are you enabling phase shift? If so, make sure to account when TBPHS is greater than your new CMP values so you don't miss any events.

    Best,

    Ryan Ma