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TMS320F28377D: epwm synchronization

nirvana_xun
Intellectual 535 points

Part Number: TMS320F28377D

if i use ePWM6/7/8 as a group to drive a bridge and use ePWM9/10/11 as a group to drive another bridge. if i do not enable ePWM4/5 how can i generate a sync signal to sychronize the six ePWM modules. it seems that synchronization groups are fixed , i can not change the sequence as i wish

4cb9e60ad09dac20c60dbb09d98c8482.png

  • 0
    Intellectual 535 points

    ① TBCTR synchronization can be set by using ePWMxSYNCIN signal, in TRM there is a pic show the syncronization path as follow, does this pic mean that only epwm1,4,7,10 can be connected to a selected external ePWMxSYNCIN signal and in other epwm modules the connection is fixed, user can only select ePWMxSYNCOUT.

    ②global load feature is used to sync different ePWM modules for shadow registers loading, the cnt_zro means the TBCTR of current module? so the sync means cmpA may sync with TBPRD?
    ③ePWMLINK feature means that sync all the cmpAx with the same value at the same time? so if developing a three phase system and epwm modules may use different cmpa values, this feature is useless in this case?

  • 0 in reply to nirvana_xun
    TI__Intellectual 2690 points

    Hi Nirvana,

    Looking into it. Will get back to you ASAP.

    Thanks

    Srikanth

  • 0 in reply to Srikanth Yerra
    TI__Intellectual 2690 points

    Hi Nirvana,

    nirvana_xun said:
    TBCTR synchronization can be set by using ePWMxSYNCIN signal, in TRM there is a pic show the syncronization path as follow, does this pic mean that only epwm1,4,7,10 can be connected to a selected external ePWMxSYNCIN signal and in other epwm modules the connection is fixed, user can only select ePWMxSYNCOUT

    Yes, you should follow the above sync scheme for this device and please be advised when configuring the sync chain propagation path using  make sure that the longest path does not exceed four ePWM/eCAP modules. 

    May I know why don't you want to use the existing groups to drive the Bridges? Have you looked at our next gen devices such as F28P65x that has very flexible ePWM synch scheme.

    nirvana_xun said:
    global load feature is used to sync different ePWM modules for shadow registers loading, the cnt_zro means the TBCTR of current module? so the sync means cmpA may sync with TBPRD?

    The Global Load feature synchronizes when shadow registers (like CMPA, CMPB, TBPRD) are loaded into their active counterparts. This ensures that parameter changes take effect at the same time across multiple PWM modules.

    How Global Load Works
    • When you write to shadow registers (e.g., CMPA, CMPB, TBPRD), the values don't immediately affect the PWM output
    • The values are transferred from shadow registers to active registers based on specific events
    • CNT_ZERO refers to the local module's TBCTR reaching zero 
    • Other options include CNT_PRD, CNT_ZERO_PRD, and external sync signals
    nirvana_xun said:
    ePWMLINK feature means that sync all the cmpAx with the same value at the same time? so if developing a three phase system and epwm modules may use different cmpa values, this feature is useless in this case?

    Yes, with EPWMXLINK feature you can link CMPA, CMPB, CMPC and TBPRD of all ePWM modules. For your application with different CMPA values you should not link CMP values instead you should individually program each ePWM module with its unique compare values. But you can still link TBPRD of all PWMs as they are running at same switching frequency.