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CCS/TMS320F28379D: Long Pulse from PWM updating PHS and CMP at same time.

Tianxiang Chen
Prodigy 140 points

Part Number: TMS320F28379D

Tool/software: Code Composer Studio

Hello I am trying to have a PWM updating from 28379D controller.

I have to update PHS and CMPA, CMPB at the same time but some time I will encounter issue. Here is my code:

EPwm7Regs.TBPRD = PRD7;

EPwm7Regs.CMPA.bit.CMPA = CMPA;

EPwm7Regs.CMPB.bit.CMPB = CMPB;

I used shadow load mode so the value should load while counter=0; My PRD value will change from 830 to 769, and CMPA from 366 to 345, CMPB from 781 to 730. In real test, I feel in some case which happens a lot, PRD is updated but CMPA and CMPB is not. In this case CMPB(781) is larger than new PRD(769), and will cause a long pulse. Is there any way for PRD and CMP to let them load or update at the same time?

Tianxiang Chen

  • 0
    TI__Guru 52200 points

    You have the option to use Global load mode.

  • 0 in reply to Nima Eskandari
    Prodigy 140 points

    Hi Nima,

    Thanks for your reply. For global load mode, my understand is it will load PRD and CMP at same time no matter what shadow reg have. But here I want to update PRD and CMP value in my interrupt first, then let it load at next counter=0 event.

    If I use global mode and software force load, I cannot guarantee it will load at next counter=0 event; If I use global mode and counter=0 event load, case will same as if I do not have global mode as my shadow mode of CMP and PRD will load on counter =0 event anyway. 

    To be more spicific, here the case is, shadow to active load occur after I have "EPwm7Regs.TBPRD = PRD7;" and before "EPwm7Regs.CMPA.bit.CMPA = CMPA;", and shadow to active load occur after I update all my update.

    Thanks, 

    Tianxiang

  • 0 in reply to Nima Eskandari
    Prodigy 140 points

    Hi Nima,

    Thanks for your reply. For global load mode, my understand is it will load PRD and CMP at same time no matter what shadow reg have. But here I want to update PRD and CMP value in my interrupt first, then let it load at next counter=0 event.

    If I use global mode and software force load, I cannot guarantee it will load at next counter=0 event; If I use global mode and counter=0 event load, case will same as if I do not have global mode as my shadow mode of CMP and PRD will load on counter =0 event anyway. 

    To be more spicific, here the case is, shadow to active load occur after I have "EPwm7Regs.TBPRD = PRD7;" and before "EPwm7Regs.CMPA.bit.CMPA = CMPA;", and shadow to active load occur after I update all my update.

    Thanks, 

    Tianxiang

  • 0 in reply to Tianxiang Chen
    TI__Guru 52200 points

    Yes, but I do think that is why we originally implement the Global load feature. Give it a try with load at CTR=ZERO as the trigger for the global load. This will ensure there was no error in the initialization code.