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piccolo 28035 Time Base Status Register (TBSTS.bit.SYNC)

Epic Vancouver
Intellectual 885 points

I am facing the following problem:

 I am using TMS320F28035.

I use an external sync signal (logic low) to sync EPWM4.

From the PWM waveforms created, I can tell that the EPWM4 is synced to that signal very well.

I want to use the sync status register, TBSTS, to get the sync status. However, the bit TBSTS.bit.SYNC is always 0 even when EPWM4 is synced.

Does anyone know why?

Thank you.

 RE: 28035 EPWM datasheet Time-Base Status Register (TBSTS) Field Descriptions

15:3 Reserved Reserved.


2      CTRMAX (Read only)

1      SYNCI(R/W)  Input Synchronization Latched Status

        Writing a 0 will have no effect. Reading a 0 indicates no external synchronization event has occurred.
        Reading a 1 on this bit indicates that an external synchronization event has occurred (EPWMxSYNCI).

        Writing a 1 to this bit will clear the latched event.


0    CTRDIR (R) 
       0 Time-Base Counter is currently counting down.
       1 Time-Base Counter is currently counting up.

  • 0
    TI__Guru* 81661 points

    Hi,

    You are wanting to use an external signal to sync ePWM4 - only ePWM1 has its SYNCI brought in on a pin from an external signal, however.

    From the ePWM module reference guide:

     

    EPWMxSYNCI Time-base synchronization input.

    Input pulse used to synchronize the time-base counter with the counter of ePWM module earlier in the

    synchronization chain. An ePWM peripheral can be configured to use or ignore this signal. For the first ePWM

    module (EPWM1) this signal comes from a device pin. For subsequent ePWM modules this signal is passed

    from another ePWM peripheral. For example, EPWM2SYNCI is generated by the ePWM1 peripheral,

    EPWM3SYNCI is generated by ePWM2 and so forth.

     

     

    So if you are bringing in your sync signal on the ePWM1 SYNCI pin, check the PWM1 TBSTS register and see if SYNCI is showing up there. Also double check that the GPIO MUX has this pin selected as ePWM1SYNCI.

     Figure 7 in the ePWM reference guide shows the sync scheme for the chain of ePWMs - if you want ePWM1 to pass on the external sync signal so you get it at ePWM4 you need to make sure that SYNCOSEL is set to 00 - EPWMxSYNC and pass the sync signal along through the chain this way.

    I hope this helps!

    Regards,

    Katie

     

     

  • 0 in reply to Katie Pier
    Prodigy 10 points

    Hi,

    I also use Picollo F28035 controller and I have two questions regarding EPWMSYNCI input?

    What is the minimum EPWMSYNCI pulse width which would effectively synchronize ePWM1 base timer?

    Is the signal EPWMSYNCI active low or active high?

    Thanks in advanced

    Kind regards

    Marko