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AM2634: CMPSS-B always tripping PWM driver output without CMPSS-B error

Sue A
Intellectual 320 points

Part Number: AM2634

Hi TI,

Request your immediate assistance on this issue as it has held up product testing for our customers.

We have configured CMPSS -B1 comparators and providing the latched output from the comparator to the PWM module via EPWMXBAR to trip the PWM outputs if there are comparator errors. During initialization, after we initialize all the drivers, we clear all the PWM trip zone, CMPSS and EPWMXBAR flags so there are no latched false start up errors. We have verified that CMPSSB_COMPSTS register reads 0 before we request for PWM output. However, even when there are no CMPSS errors, the PWM does not start and remains tripped. When I configured the CMPSS output to be ASYNC, SYNC or Digital Filter output, we get PWM output. But we don't get PWM output with CMPSS Latched outputs even though CMPSSB_COMPSTS reads 0.  Please advise how to resolve this issue. 
I have looked through the technical manual and registers, everything seems fine. I am not sure where the latch is not getting cleared.

Below are my configurations - 

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void Drivers_epwmXbarOpen(void)
{
    /* EPWM XBAR */
    SOC_xbarSelectPWMXBarInputSource(CSL_CONTROLSS_PWMXBAR_U_BASE, 3, 0, ( EPWM_XBAR_CMPSSB1_CTRIPH | EPWM_XBAR_CMPSSB1_CTRIPL), 0, 0, 0, 0, 0, 0, 0);
    // SOC_xbarInvertPWMXBarOutputSignalBeforeLatch(CSL_CONTROLSS_PWMXBAR_U_BASE, 0);
}

 

  • 0
    TI__Mastermind 21971 points

    Hi Sue,

    Per the initialization sequence from the TRM, you are following the correct sequence with the only difference being that the configOutputsHigh and configOutputsLow is recommended to be called at the very end after clearing the COMPSTS register

    What does the input to the CMPSS look like? Is there a voltage offset? Have you tried adjusting the filter threshold to a higher value?

    Regards,

    peter