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TMS320F28335: EPWM for 0% and 100% duty

Wayne Huang
Genius 16435 points
Part Number: TMS320F28335


Tool/software:

Hi champs,

I am asking this for our customer.

The user has used F28335 for many years and just wants to output 0% duty for their EPWM setting using up-down count.

The user is aware of 

3.2.4.4 Waveforms for Common Configurations

of the TRM.

But the user thinks the workaround in the app note SPRAAI1 is too complicated.

Questions:

1. The user set CMPA/CMPB load from shadow to active at ZRO.

Can the user just use CMPA/CMPB = TBPRD?

In real testing, the user does not find anything wrong, but wants TI to confirm this.

2. 

The user sets CMPA/CMPB load from shadow to active at PRD.

Can the user just use CMPA/CMPB = 0?

In real testing, the user does not find anything wrong, but wants TI to confirm this.

  • 0
    TI__Genius 16435 points

    Hi champs,

    Do you have any update?

  • 0 in reply to Wayne Huang
    TI__Intellectual 2187 points

    Hi Wayne Huang,

    To answer your questions,

    On shadow loading, if the Shadow loadmode is zero and user loads a TBPRD value or loadmode is period and use loads a Zero value, then they should be loaded properly in the current period. 

    And on 0 and 100% duty cycle requirements, if user is following the priority tables at 3.2.4.3 Action Qualifier Event Priority, then it should be good enough.

    One key take away is the following. if user's configurations match these, then the system should be fine.

    1. If "Load on Zero" is used, user can use CMP values from 1 to TBPRD.
    2. If "Load on Period" is used, user can use CMP values from 0 to TBPRD-1.

    Hope this helps.

    Thanks and regards,

    Madhava