TMS320F28379D: EPWM1的TBPRD从影子寄存器加载方式实际效果与设置效果不一致

fan jun

Part Number: TMS320F28379D

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interrupt void UserISR(void)
{
    if(syncAdjEna == 1)
    {
        EALLOW;
        EPwm1Regs.TBCTL.bit.PRDLD = 0;                      //Enable shadow
        EPwm1Regs.TBCTL2.bit.PRDLDSYNC = 0;             //TBCTR = 0:shadow->active
        EPwm1Regs.TBPRD = 4166*2;
        EDIS;
        GpioDataRegs.GPBTOGGLE.bit.GPIO38 = 1;
        cnt = 15;
        syncAdjEna = 0;
    }
    if(cnt > 1)
    {
        if(cnt == 14)
        {
            EALLOW;
            EPwm1Regs.TBCTL.bit.PRDLD = 0;                      //Enable shadow
            EPwm1Regs.TBCTL2.bit.PRDLDSYNC = 0;
            EPwm1Regs.TBPRD = 4166;
XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX

interrupt void UserISR(void)
{
    if(syncAdjEna == 1)
    {
        EALLOW;
        EPwm1Regs.TBCTL.bit.PRDLD = 0;                      //Enable shadow
        EPwm1Regs.TBCTL2.bit.PRDLDSYNC = 0;             //TBCTR = 0:shadow->active
        EPwm1Regs.TBPRD = 4166*2;
        EDIS;
        GpioDataRegs.GPBTOGGLE.bit.GPIO38 = 1;
        cnt = 15;
        syncAdjEna = 0;
    }
    if(cnt > 1)
    {
        if(cnt == 14)
        {
            EALLOW;
            EPwm1Regs.TBCTL.bit.PRDLD = 0;                      //Enable shadow
            EPwm1Regs.TBCTL2.bit.PRDLDSYNC = 0;
            EPwm1Regs.TBPRD = 4166;
            EDIS;
            GpioDataRegs.GPBTOGGLE.bit.GPIO38 = 1;
        }
        else if(cnt == 13)
        {
            GpioDataRegs.GPBTOGGLE.bit.GPIO38 = 1;
        }
        else if(cnt == 12)
        {
            GpioDataRegs.GPBTOGGLE.bit.GPIO38 = 1;
        }
        cnt--;
        if(cnt == 2) cnt = 0; 
    }
    PieCtrlRegs.PIEACK.all |= PIEACK_GROUP11;
}

目标：UserISR中断中增大EPWM1 TBPRD值（4166*2），下一次进UserISR中断再恢复为原值（4166）

配置基础：EPWM1计数器采用向上向下计数方式，TR=0和TR=PRD时触发EPWM1SOCA，SOCA触发ADC中断，ADCAINT1触发CLA中断，每两次CLA中断触发一次UserISR中断（频率24K，一个周期41.65us）并且翻转IO电平（以此电平作为过零点信号，波形为蓝色所示），UserISR中断里改变TBPRD前翻转另一个IO电平（波形为绿色所示），配置为：

Fullscreen

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        EPwm1Regs.TBCTL.bit.PRDLD = 0;                      //Enable shadow
        EPwm1Regs.TBCTL2.bit.PRDLDSYNC = 0;             //TBCTR = 0:shadow->active
XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX

        EPwm1Regs.TBCTL.bit.PRDLD = 0;                      //Enable shadow
        EPwm1Regs.TBCTL2.bit.PRDLDSYNC = 0;             //TBCTR = 0:shadow->active

根据配置，效果应该是蓝色波形其中一个周期变长（时间为41.65*2us），但实际效果为其中两个周期变长（时间为62us，即为41.65us的1.5倍，看起来似乎TBPRD从影子寄存器加载时机并不是设置的零点，而是顶点，这是为什么？），如下图所示：