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CCS/TMS320F28377S: Relation PWM Period - System clock - TBCLK clock

Jonas Hemmer
Intellectual 460 points
Part Number: TMS320F28377S
Other Parts Discussed in Thread: CONTROLSUITE

Tool/software: Code Composer Studio

Hallo, I am new here.


I use a TMS320F28377S LaunchPad Development Kit.


I loaded the Project hrpwm_duty_sfo_cpu01 from the controlSUITE Examples( controlSUITE-> device_support->v210->hprwm_duty_sfo_v8->cpu01->hrpwm_duty_sfo_cpu01).

The Problem i have is that the expectet PWM Period is not the PWM Period i measure.

On page 1442/2352 of the Technical Reference Manual there is a note that the EPWMCLK = SYSCLKOUT/2.

So EPWMCLK should run with 100 MHz ( 10 ns).

The HSPCLKDIV and CLKDIV Divider are set to the factor 1. So the TBCLK Clock should run with 100 MHz (10 ns) refer to page 1443/2352  (Technical Reference Manual)

So i would expect that call the HRPWM_Config function with a value of 10 would generate a PWM Periode of 10*10ns= 100 ns.

The real PWM Period (measured ) is 200 ns.

I don't know why . Can anybody explain why the PWM Period is 200ns instead of 100ns.

I did nothing change in the project example. Using Code Composer Studio  Version: 6.2.0.00050 

HRPWM_Config(10);   // ePWMx target

void HRPWM_Config(period)
{
    Uint16 j;

    //
    // ePWM channel register configuration with HRPWM
    // ePWMxA / ePWMxB toggle low/high with MEP control on Rising edge
    //
    for (j=1;j<PWM_CH;j++)
    {
        (*ePWM[j]).TBCTL.bit.PRDLD = TB_SHADOW;  // set Immediate load
        (*ePWM[j]).TBPRD = period-1;             // PWM frequency = 1 / period
        (*ePWM[j]).CMPA.bit.CMPA = period / 2;   // set duty 50% initially
        (*ePWM[j]).CMPA.bit.CMPAHR = (1 << 8);   // initialize HRPWM extension
        (*ePWM[j]).CMPB.bit.CMPB = period / 2;   // set duty 50% initially
        (*ePWM[j]).CMPB.all |= (1 << 8);         // initialize HRPWM extension
        (*ePWM[j]).TBPHS.all = 0;
        (*ePWM[j]).TBCTR = 0;

        (*ePWM[j]).TBCTL.bit.CTRMODE = TB_COUNT_UP;
        (*ePWM[j]).TBCTL.bit.PHSEN = TB_DISABLE;
        (*ePWM[j]).TBCTL.bit.SYNCOSEL = TB_SYNC_DISABLE;
        (*ePWM[j]).TBCTL.bit.HSPCLKDIV = TB_DIV1;
        (*ePWM[j]).TBCTL.bit.CLKDIV = TB_DIV1;
        (*ePWM[j]).TBCTL.bit.FREE_SOFT = 11;

        (*ePWM[j]).CMPCTL.bit.LOADAMODE = CC_CTR_ZERO;
        (*ePWM[j]).CMPCTL.bit.LOADBMODE = CC_CTR_ZERO;
        (*ePWM[j]).CMPCTL.bit.SHDWAMODE = CC_SHADOW;
        (*ePWM[j]).CMPCTL.bit.SHDWBMODE = CC_SHADOW;


        (*ePWM[j]).AQCTLA.bit.ZRO = AQ_SET;      // PWM toggle high/low
        (*ePWM[j]).AQCTLA.bit.CAU = AQ_CLEAR;
        (*ePWM[j]).AQCTLB.bit.ZRO = AQ_SET;
        (*ePWM[j]).AQCTLB.bit.CBU = AQ_CLEAR;

        EALLOW;
        (*ePWM[j]).HRCNFG.all = 0x0;
        (*ePWM[j]).HRCNFG.bit.EDGMODE = HR_FEP;  // MEP control on falling edge
        (*ePWM[j]).HRCNFG.bit.CTLMODE = HR_CMP;
        (*ePWM[j]).HRCNFG.bit.HRLOAD  = HR_CTR_ZERO;
        (*ePWM[j]).HRCNFG.bit.EDGMODEB = HR_FEP; // MEP control on falling edge
        (*ePWM[j]).HRCNFG.bit.CTLMODEB = HR_CMP;
        (*ePWM[j]).HRCNFG.bit.HRLOADB  = HR_CTR_ZERO;
        #if (AUTOCONVERT)
        (*ePWM[j]).HRCNFG.bit.AUTOCONV = 1;      // Enable auto-conversion
                                                 // logic
        #endif
        (*ePWM[j]).HRPCTL.bit.HRPE = 0; // Turn off high-resolution period
                                        // control.
        EDIS;
    }
}


Thank you very much,

Jonas