[讨论] 求助：LED灯交替闪烁实验中epwm中断作用

本人刚接触dsp，不明白LED灯交替闪烁实验中为什么用epwm中断，请高手指点一下。

 void main(void)
{Uint16 i = 0x55;
   InitSysCtrl();

   DINT;

   InitPieCtrl();

   IER = 0x0000;
   IFR = 0x0000;

   InitPieVectTable();

   EALLOW;  // This is needed to write to EALLOW protected registers
   PieVectTable.EPWM1_INT = &epwm1_timer_isr;
   PieVectTable.EPWM2_INT = &epwm2_timer_isr;
   PieVectTable.EPWM3_INT = &epwm3_timer_isr;
   EDIS;    // This is needed to disable write to EALLOW protected registers

   InitEPwmTimer();    // For this example, only initialize the ePWM Timers

//// This function must reside in RAM
   InitFlash();

// Initalize counters:
   EPwm1TimerIntCount = 0;
   EPwm2TimerIntCount = 0;
   EPwm3TimerIntCount = 0;
   LoopCount = 0;

// Enable CPU INT3 which is connected to EPWM1-3 INT:
   IER |= M_INT3;

// Enable EPWM INTn in the PIE: Group 3 interrupt 1-3
   PieCtrlRegs.PIEIER3.bit.INTx1 = PWM1_INT_ENABLE;
   PieCtrlRegs.PIEIER3.bit.INTx2 = PWM2_INT_ENABLE;
   PieCtrlRegs.PIEIER3.bit.INTx3 = PWM3_INT_ENABLE;

// Enable global Interrupts and higher priority real-time debug events:
   EINT;   // Enable Global interrupt INTM
   ERTM;   // Enable Global realtime interrupt DBGM

//////Initial XZONE//////  
   InitXintf();

// Step 6. IDLE loop. Just sit and loop forever (optional):
   for(;;)
   {
       // This loop will be interrupted, so the overall
       // delay between pin toggles will be longer.
       DELAY_US(DELAY);
    LoopCount++;
       LED = i;
    i = ~i;
   }

}

void InitEPwmTimer()
{

   EALLOW;
   SysCtrlRegs.PCLKCR0.bit.TBCLKSYNC = 0;      // Stop all the TB clocks
   EDIS;

   // Setup Sync
   EPwm1Regs.TBCTL.bit.SYNCOSEL = TB_SYNC_IN;  // Pass through
   EPwm2Regs.TBCTL.bit.SYNCOSEL = TB_SYNC_IN;  // Pass through
   EPwm3Regs.TBCTL.bit.SYNCOSEL = TB_SYNC_IN;  // Pass through

   // Allow each timer to be sync'ed

   EPwm1Regs.TBCTL.bit.PHSEN = TB_ENABLE;
   EPwm2Regs.TBCTL.bit.PHSEN = TB_ENABLE;
   EPwm3Regs.TBCTL.bit.PHSEN = TB_ENABLE;

   EPwm1Regs.TBPHS.half.TBPHS = 100;
   EPwm2Regs.TBPHS.half.TBPHS = 200;
   EPwm3Regs.TBPHS.half.TBPHS = 300;

   EPwm1Regs.TBPRD = PWM1_TIMER_TBPRD;
   EPwm1Regs.TBCTL.bit.CTRMODE = TB_COUNT_UP;    // Count up
   EPwm1Regs.ETSEL.bit.INTSEL = ET_CTR_ZERO;     // Select INT on Zero event
   EPwm1Regs.ETSEL.bit.INTEN = PWM1_INT_ENABLE;  // Enable INT
   EPwm1Regs.ETPS.bit.INTPRD = ET_1ST;           // Generate INT on 1st event

   EPwm2Regs.TBPRD = PWM2_TIMER_TBPRD;
   EPwm2Regs.TBCTL.bit.CTRMODE = TB_COUNT_UP;     // Count up
   EPwm2Regs.ETSEL.bit.INTSEL = ET_CTR_ZERO;      // Enable INT on Zero event
   EPwm2Regs.ETSEL.bit.INTEN = PWM2_INT_ENABLE;   // Enable INT
   EPwm2Regs.ETPS.bit.INTPRD = ET_2ND;            // Generate INT on 2nd event

   EPwm3Regs.TBPRD = PWM3_TIMER_TBPRD;
   EPwm3Regs.TBCTL.bit.CTRMODE = TB_COUNT_UP;     // Count up
   EPwm3Regs.ETSEL.bit.INTSEL = ET_CTR_ZERO;      // Enable INT on Zero event
   EPwm3Regs.ETSEL.bit.INTEN = PWM3_INT_ENABLE;   // Enable INT
   EPwm3Regs.ETPS.bit.INTPRD = ET_3RD;            // Generate INT on 3rd event

   EALLOW;
   SysCtrlRegs.PCLKCR0.bit.TBCLKSYNC = 1;         // Start all the timers synced
   EDIS;

}

// This ISR MUST be executed from RAM as it will put the Flash into Sleep
// Interrupt routines uses in this example:
interrupt void epwm1_timer_isr(void)
{

   // Put the Flash to sleep
   FlashRegs.FPWR.bit.PWR = FLASH_SLEEP;

   EPwm1TimerIntCount++;

   // Clear INT flag for this timer
   EPwm1Regs.ETCLR.bit.INT = 1;

   // Acknowledge this interrupt to receive more interrupts from group 3
   PieCtrlRegs.PIEACK.all = PIEACK_GROUP3;
}

// This ISR MUST be executed from RAM as it will put the Flash into Standby
interrupt void epwm2_timer_isr(void)
{
   EPwm2TimerIntCount++;

    // Put the Flash into standby
    FlashRegs.FPWR.bit.PWR = FLASH_STANDBY;

   // Clear INT flag for this timer
   EPwm2Regs.ETCLR.bit.INT = 1;

   // Acknowledge this interrupt to receive more interrupts from group 3
   PieCtrlRegs.PIEACK.all = PIEACK_GROUP3;
}

interrupt void epwm3_timer_isr(void)
{
   Uint16 i;

   EPwm3TimerIntCount++;

    // Short Delay to simulate some ISR Code
    for(i = 1; i < 0x01FF; i++) {}

   // Clear INT flag for this timer
   EPwm3Regs.ETCLR.bit.INT = 1;

   // Acknowledge this interrupt to receive more interrupts from group 3
   PieCtrlRegs.PIEACK.all = PIEACK_GROUP3;
}