求教怎么用28335cap中断启动电机

在没有上升沿和下降沿的时候电机无法启动，不能进入中断
interrupt void ISRCap1(void)
{

        GpioCtrlRegs.GPAMUX2.bit.GPIO24=0;//设定cap1~3为gpio
           GpioCtrlRegs.GPAMUX2.bit.GPIO25=0;
           GpioCtrlRegs.GPAMUX2.bit.GPIO26=0;
           GpioCtrlRegs.GPADIR.bit.GPIO24=0;//设定cap1~3为输入
        GpioCtrlRegs.GPADIR.bit.GPIO25=0;
        GpioCtrlRegs.GPADIR.bit.GPIO26=0;
           capstastus=(GpioDataRegs.GPADAT.all&0x07000000)>>24;

    GpioCtrlRegs.GPAMUX2.bit.GPIO24=1;//设定cap1~3为cap
           GpioCtrlRegs.GPAMUX2.bit.GPIO25=1;
           GpioCtrlRegs.GPAMUX2.bit.GPIO26=1;
   // Acknowledge this interrupt to receive more interrupts from group 1
    PieCtrlRegs.PIEACK.all = PIEACK_GROUP4;//0x0001赋给12组中断ACKnowledge寄存器，对其全部清除，不接受其他中断

    ECap1Regs.ECCLR.all=0xFFFF;//clear all flag 写0XFFFF对CAP1中断清除寄存器进行清除操作
    ECap2Regs.ECCLR.all=0xFFFF;
    ECap3Regs.ECCLR.all=0xFFFF;

}

void SetCap1Mode(void)
{
  ECap1Regs.ECCTL1.bit.CAP1POL = EC_RISING;
  ECap1Regs.ECCTL1.bit.CAP2POL = EC_FALLING;
  ECap1Regs.ECCTL1.bit.CAP3POL = EC_RISING;
  ECap1Regs.ECCTL1.bit.CAP4POL = EC_FALLING;
  ECap1Regs.ECCTL1.bit.CTRRST1 = EC_DELTA_MODE;
  ECap1Regs.ECCTL1.bit.CTRRST2 = EC_DELTA_MODE;
  ECap1Regs.ECCTL1.bit.CTRRST3 = EC_DELTA_MODE;
  ECap1Regs.ECCTL1.bit.CTRRST4 = EC_DELTA_MODE;
  ECap1Regs.ECCTL1.bit.CAPLDEN = EC_ENABLE;
  ECap1Regs.ECCTL1.bit.PRESCALE = EC_DIV1;
  ECap1Regs.ECCTL2.bit.CAP_APWM = EC_CAP_MODE;
  ECap1Regs.ECCTL2.bit.CONT_ONESHT = EC_ONESHOT;
  ECap1Regs.ECCTL2.bit.SYNCO_SEL = EC_SYNCO_DIS;
  ECap1Regs.ECCTL2.bit.SYNCI_EN = EC_DISABLE;
  ECap1Regs.ECEINT.all=0x0000;//stop all interrupt
  ECap1Regs.ECCLR.all=0xFFFF;//clare all flag
  ECap1Regs.ECCTL2.bit.TSCTRSTOP = EC_RUN;// 启动
  ECap1Regs.ECEINT.bit.CEVT1=1;// Enable cevt1 interrupt
  ECap1Regs.ECEINT.bit.CEVT2=1;// Enable cevt2 interrupt
  ECap1Regs.ECEINT.bit.CEVT3=1;// Enable cevt3 interrupt
  ECap1Regs.ECEINT.bit.CEVT4=1;// Enable cevt4 interrupt
}