TMS320F28335: 请问为什么我使用pwm发波时，波会出现一个周期，然后小时，过几秒后再出再消失

如题

interrupt void cpu_timer1_isr(void)
{

                 EPwm1Regs.CMPA.half.CMPA=table[a];
                 EPwm2Regs.CMPA.half.CMPA=table[a];

if(++a>=400)a=0;
  //  CpuTimer1.InterruptCount++;
   // EDIS;//直接确认，无需PIE
}

这是epwm的

void epwm1_gpio()
{
      EALLOW;
      GpioCtrlRegs.GPAPUD.bit.GPIO0=1;
      GpioCtrlRegs.GPAPUD.bit.GPIO1=1;

      GpioCtrlRegs.GPAMUX1.bit.GPIO0=1;//复用IO模式
      GpioCtrlRegs.GPAMUX1.bit.GPIO1=1;
      EDIS;
}

void epwm2_gpio()
{
    EALLOW;
    GpioCtrlRegs.GPAPUD.bit.GPIO2=1;
    GpioCtrlRegs.GPAPUD.bit.GPIO3=1;

    GpioCtrlRegs.GPAMUX1.bit.GPIO2=1;//复用IO模式
    GpioCtrlRegs.GPAMUX1.bit.GPIO3=1;
    EDIS;
}
void epwm1_init()
{
    EPwm1Regs.TBPRD=750;//f=TBPRDx1/时钟频率
    EPwm1Regs.TBPHS.half.TBPHS=0;
    EPwm1Regs.TBCTR=0x000;

    EPwm1Regs.CMPA.half.CMPA=375;
    EPwm1Regs.CMPB=375;

    EPwm1Regs.TBCTL.bit.CLKDIV=0;
    EPwm1Regs.TBCTL.bit.HSPCLKDIV=101;
    EPwm1Regs.TBCTL.bit.PHSEN=0;
    EPwm1Regs.TBCTL.bit.CTRMODE=TB_COUNT_UP;
    EPwm1Regs.TBCTL.bit.PRDLD=0;
   // EPwm1Regs.TBCTL.bit.SYNCOSEL=1;

    EPwm1Regs.CMPCTL.bit.SHDWAMODE= 0;
    EPwm1Regs.CMPCTL.bit.SHDWBMODE= 0;
    EPwm1Regs.CMPCTL.bit.LOADAMODE= 0;
    EPwm1Regs.CMPCTL.bit.LOADBMODE= 0;



    //EPwm1Regs.AQCTLA.bit.CAU=1;
    //EPwm1Regs.AQCTLA.bit.CAD=2;
    //EPwm1Regs.AQCTLB.bit.CAU=1;
    //EPwm1Regs.AQCTLB.bit.CAD=2;
    EPwm1Regs.AQCTLA.bit.CAU=2;
    EPwm1Regs.AQCTLA.bit.ZRO=1;
    EPwm1Regs.AQCTLB.bit.CAU=2;
    EPwm1Regs.AQCTLB.bit.ZRO=1;


   // EPwm1Regs.ETCLR.bit.INT=1;

 // EPwm1Regs.DBCTL.bit.IN_MODE=2;
    EPwm1Regs.DBCTL.bit.OUT_MODE=3;
    EPwm1Regs.DBCTL.bit.POLSEL=2;
    EPwm1Regs.DBRED = 5;
    EPwm1Regs.DBFED = 5;
}
void epwm2_init()
{
  EPwm2Regs.TBPRD =750;
  EPwm2Regs.TBPHS.half.TBPHS=0x00;
  EPwm2Regs.TBCTR=0x00;

  EPwm2Regs.CMPA.half.CMPA=375;
  EPwm2Regs.CMPB=375;

  EPwm2Regs.TBCTL.bit.CLKDIV=0;
  EPwm2Regs.TBCTL.bit.HSPCLKDIV=101;
  EPwm2Regs.TBCTL.bit.PHSEN=0;
  EPwm2Regs.TBCTL.bit.CTRMODE=TB_COUNT_UP;
  EPwm2Regs.TBCTL.bit.PRDLD=0;

  EPwm2Regs.CMPCTL.bit.LOADAMODE=0;
  EPwm2Regs.CMPCTL.bit.LOADBMODE=0;
  EPwm2Regs.CMPCTL.bit.SHDWAMODE=0;
  EPwm2Regs.CMPCTL.bit.SHDWBMODE=0;

    EPwm2Regs.AQCTLA.bit.CAU=1;
    EPwm2Regs.AQCTLA.bit.ZRO=2;
    EPwm2Regs.AQCTLB.bit.CAU=1;
    EPwm2Regs.AQCTLB.bit.ZRO=2;


  EPwm2Regs.DBCTL.bit.OUT_MODE=3;
  EPwm2Regs.DBCTL.bit.POLSEL=2;
  EPwm2Regs.DBFED=5;
  EPwm2Regs.DBRED=5;

}