TMS320F280034: EPWM4 miss output when changing frequency in sync mode

Part Number: TMS320F280034

Tool/software:

Hi experts,

My customer feedback that the EPWM4 on 280034 cannot output PWM signal when they changing the frequency with sync source from EPWM1.

I try to reproduce the issue on EVM of 280039 with the demo of "epwm_ex3_synchronization". I add the following code in the main loop (I have changed the CMPA to 300 and CMPB to 100. I disable the EPWM interrupt)

uint32_t period = 4000;

//main loop
for(;;)
    {
        for(; period > 1000;)
        {
           DEVICE_DELAY_US(2000000);
           EPWM_setTimeBasePeriod(myEPWM1_BASE, period);
           EPWM_setTimeBasePeriod(myEPWM2_BASE, period);
           EPWM_setTimeBasePeriod(myEPWM3_BASE, period);
           EPWM_setTimeBasePeriod(myEPWM4_BASE, period);
           period = period - 1500;
        }
        for(; period < 3000;)
        {
           DEVICE_DELAY_US(2000000);
           EPWM_setTimeBasePeriod(myEPWM1_BASE, period);
           EPWM_setTimeBasePeriod(myEPWM2_BASE, period);
           EPWM_setTimeBasePeriod(myEPWM3_BASE, period);
           EPWM_setTimeBasePeriod(myEPWM4_BASE, period);
           period = period + 1500;
        }

    }

And find that, sometimes when period changed from 2500 to 1000, the EPWM4 output will miss.

Yellow: pwm1; blue: pwm2; green: pwm3; purple: pwm4

normal:

frequency change

I exchange the TBTHS value between epwm3 and epwm4, and also find the same result:

Any suggestions for this issue? Are there any special features for EPWM4?

Thanks,

Leo