TMS320F28P659DK-Q1: PWM outputs overriding function

Part Number: TMS320F28P659DK-Q1
Other Parts Discussed in Thread: SYSCONFIG

Hi Texas Team,

I am currently testing a three-phase inverter.

I have the outputs working, but I am struggling to find the proper method to override the PWM outputs using the Trip Zone. Specifically, I need three PWMs with complementary outputs that can be simultaneously forced to zero (or released) based on software control.

The three PWMs are configured identically, except that PWM_A generates a sync out signal, while PWM_B and PWM_C use it as a sync in signal. They operate as expected, but when I call the functions PwmRunModeOff and PwmRunModeOn to control the override, the code sometimes only turns off one or two outputs instead of all three.

The relevant code is attached below:

void PwmRunModeOff(void) {
    uint16_t i;

    // Optional: freeze TBCLK if you want simultaneity across modules
    // SysCtl_disablePeripheral(SYSCTL_PERIPH_CLK_TBCLKSYNC);

    for (i = 0; i < sizeof(kPwmBases) / sizeof(kPwmBases[0]); ++i) {
        const uint32_t base = kPwmBases[i];

        EALLOW;
        // Ensure trip actions will force final outputs LOW
        EPWM_setTripZoneAction(base, EPWM_TZ_ACTION_EVENT_TZA, EPWM_TZ_ACTION_LOW);
        EPWM_setTripZoneAction(base, EPWM_TZ_ACTION_EVENT_TZB, EPWM_TZ_ACTION_LOW);

        // Prevent a TZ ISR from clearing OST while we hold
        EPWM_disableTripZoneInterrupt(base, EPWM_TZ_INTERRUPT_OST | EPWM_TZ_INTERRUPT_CBC);

        // Make sure AQ continuous SW forces are not active
        EPWM_setActionQualifierContSWForceAction(base, EPWM_AQ_OUTPUT_A, EPWM_AQ_SW_DISABLED);
        EPWM_setActionQualifierContSWForceAction(base, EPWM_AQ_OUTPUT_B, EPWM_AQ_SW_DISABLED);

        // Clear stale latches so our new OST is the only one observed
        EPWM_clearTripZoneFlag(base,
                               EPWM_TZ_INTERRUPT_OST | EPWM_TZ_INTERRUPT_CBC |
                               EPWM_TZ_FLAG_DCAEVT1 | EPWM_TZ_FLAG_DCAEVT2 |
                               EPWM_TZ_FLAG_DCBEVT1 | EPWM_TZ_FLAG_DCBEVT2);

        // Latch OST (post-deadband outputs go LOW)
        EPWM_forceTripZoneEvent(base, EPWM_TZ_FORCE_EVENT_OST);
        EDIS;
    }

    // Verify latch once
    for (i = 0; i < sizeof(kPwmBases) / sizeof(kPwmBases[0]); ++i) {
        const uint32_t base = kPwmBases[i];

        if ((EPWM_getTripZoneFlagStatus(base) & EPWM_TZ_FLAG_OST) == 0U) {
            EALLOW;
            EPWM_forceTripZoneEvent(base, EPWM_TZ_FORCE_EVENT_OST);
            EDIS;
        }
    }

    // SysCtl_enablePeripheral(SYSCTL_PERIPH_CLK_TBCLKSYNC);

    turn_off_drivers();
}

void PwmRunModeOn(void) {
    uint16_t i;

    // Optional: align release to TBCTR==0 on your master for a clean first edge
    // while (EPWM_getTimeBaseCounter(PWM_A_BASE) != 0U) {}

    for (i = 0; i < sizeof(kPwmBases) / sizeof(kPwmBases[0]); ++i) {
        const uint32_t base = kPwmBases[i];

        EALLOW;
        // Clear OST/CBC & DC flags so PWM resumes
        EPWM_clearTripZoneFlag(base,
                               EPWM_TZ_INTERRUPT_OST | EPWM_TZ_INTERRUPT_CBC |
                               EPWM_TZ_FLAG_DCAEVT1 | EPWM_TZ_FLAG_DCAEVT2 |
                               EPWM_TZ_FLAG_DCBEVT1 | EPWM_TZ_FLAG_DCBEVT2);

        // Ensure no AQ SW force
        EPWM_setActionQualifierContSWForceAction(base, EPWM_AQ_OUTPUT_A, EPWM_AQ_SW_DISABLED);
        EPWM_setActionQualifierContSWForceAction(base, EPWM_AQ_OUTPUT_B, EPWM_AQ_SW_DISABLED);

        // Unmask TZ interrupts again if you use them elsewhere
        EPWM_enableTripZoneInterrupt(base, EPWM_TZ_INTERRUPT_OST | EPWM_TZ_INTERRUPT_CBC);
        EDIS;
    }

    turn_on_drivers();
}

Could you please advise on the correct or recommended way to implement this simultaneous, synchronized PWM override using the Trip Zone?

Thank you in advance,