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TMS320F28035: LOADAMODE and LOADBMODE

Wayne Huang
Genius 16985 points

Part Number: TMS320F28035

Dear champs,

I am asking this for our customer.

When these two registers are set to 2, it means "Load on either CTR = Zero or CTR = PRD" on the TRM.

1) What does it mean by "either CTR = Zero or CTR = PRD"?

Does that mean this point is random and not fixed?

Sometimes it happens at zero and sometimes it happens at PRD in up-down count?

Or it just means it happens at both zero and PRD, that is, it can happen twice in a PWM cycle?

2) If it cannot happen twice in a PWM cycle, how does the user get twice update at both Zero and PRD? Do you have any suggestion for them to implement? Note that they cannot double the PWM frequency.

Wayne Huang

  • 0
    TI__Mastermind 26660 points

    Hi Wayne,

    Thank you for your question. The third case you have described is correct, loading will happen at both zero and PRD. 

    Below is a piece of the shadow mode description within the TRM:

    "If the shadow register is enabled then the content of the shadow register is transferred to the active register on one of the following events as specified by the CMPCTL[LOADAMODE] and CMPCTL[LOADBMODE] register bits:

    • CTR = PRD: Time-base counter equal to the period (TBCTR = TBPRD)

    • CTR = Zero: Time-base counter equal to zero (TBCTR = 0x0000)

    • Both CTR = PRD and CTR = Zero"

    I'll go ahead and file tickets to get the wording corrected for the register descriptions and other places where the messaging is not clear.

    Best Regards,

    Marlyn