28335中断问题

老师您好！初学，不知道什么时候进入中断，为了能说明白问题，下面的例程在开发板上已经测试了，正常，是PWM控制两个LED闪烁，我只是想知道，进入中断的条件，在哪条语句中能看到满足某个条件就进入了中断啊？感谢了
#include "DSP2833x_Device.h"     // DSP2833x Headerfile Include File
#include "DSP2833x_Examples.h"   // DSP2833x Examples Include File

#define PWM1_INT_ENABLE  1
#define PWM2_INT_ENABLE  1
#define PWM3_INT_ENABLE  1
#define PWM1_tiMER_TBPRD   0x1FFF
#define PWM2_TIMER_TBPRD   0x1FFF
#define PWM3_TIMER_TBPRD   0x1FFF

#define DELAY 1000000L

interrupt void epwm1_timer_isr(void);
interrupt void epwm2_timer_isr(void);
interrupt void epwm3_timer_isr(void);
void InitEPwmTimer(void);
Uint32  EPwm1TimerIntCount;
Uint32  EPwm2TimerIntCount;
Uint32  EPwm3TimerIntCount;
Uint32  LoopCount;

void main(void)
[  
InitSysCtrl();
DINT;
InitPieCtrl();
IER = 0x0000;
IFR = 0x0000;
InitPieVectTable();
EALLOW;
   PieVectTable.EPWM1_INT = &epwm1_timer_isr;  
  PieVectTable.EPWM2_INT = &epwm2_timer_isr;   
PieVectTable.EPWM3_INT = &epwm3_timer_isr;
  EDIS;
InitEPwmTimer();
InitFlash();
EPwm1TimerIntCount = 0;   
EPwm2TimerIntCount = 0;   
EPwm3TimerIntCount = 0;   
LoopCount = 0;
  EINT;
ERTM;
InitXintf();
for(;;)
[]
]
void InitEPwmTimer()
[
   EALLOW;
   SysCtrlRegs.PCLKCR0.bit.TBCLKSYNC = 0;     
  EDIS;
   // Setup Sync  
  EPwm1Regs.TBCTL.bit.SYNCOSEL = TB_SYNC_IN;
EPwm2Regs.TBCTL.bit.SYNCOSEL = TB_SYNC_IN;
EPwm3Regs.TBCTL.bit.SYNCOSEL = TB_SYNC_IN;
   // 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;   
  EPwm1Regs.ETSEL.bit.INTSEL = ET_CTR_ZERO;   
EPwm1Regs.ETSEL.bit.INTEN = PWM1_INT_ENABLE;
  EPwm1Regs.ETPS.bit.INTPRD = ET_1ST;         
   EPwm2Regs.TBPRD = PWM2_TIMER_TBPRD;   
EPwm2Regs.TBCTL.bit.CTRMODE = TB_COUNT_UP;   
EPwm2Regs.ETSEL.bit.INTSEL = ET_CTR_ZERO;   
  EPwm2Regs.ETSEL.bit.INTEN = PWM2_INT_ENABLE;  
   EPwm2Regs.ETPS.bit.INTPRD = ET_2ND;           
   EPwm3Regs.TBPRD = PWM3_TIMER_TBPRD;
   EPwm3Regs.TBCTL.bit.CTRMODE = TB_COUNT_UP;   
   EPwm3Regs.ETSEL.bit.INTSEL = ET_CTR_ZERO;     
EPwm3Regs.ETSEL.bit.INTEN = PWM3_INT_ENABLE;  
EPwm3Regs.ETPS.bit.INTPRD = ET_3RD;           
   EALLOW;   
SysCtrlRegs.PCLKCR0.bit.TBCLKSYNC = 1;        
EDIS;
]
interrupt void epwm1_timer_isr(void)
[
   // Put the Flash to sleep   
FlashRegs.FPWR.bit.PWR = FLASH_SLEEP;
   EPwm1TimerIntCount++;   
if ((EPwm1TimerIntCount%2000)==0)   
GpioDataRegs.GPATOGGLE.bit.GPIO0 = 1;

  EPwm1Regs.ETCLR.bit.INT = 1;

PieCtrlRegs.PIEACK.all = PIEACK_GROUP3;
]

interrupt void epwm2_timer_isr(void)
[   
EPwm2TimerIntCount++;   
if ((EPwm2TimerIntCount%2000)==0)   
GpioDataRegs.GPATOGGLE.bit.GPIO1 = 1;
  FlashRegs.FPWR.bit.PWR = FLASH_STANDBY;
EPwm2Regs.ETCLR.bit.INT = 1;

PieCtrlRegs.PIEACK.all = PIEACK_GROUP3;
]
interrupt void epwm3_timer_isr(void)
[   
Uint16 i;
  EPwm3TimerIntCount++;
  for(i = 1; i < 0x01FF; i++) []
EPwm3Regs.ETCLR.bit.INT = 1;
  PieCtrlRegs.PIEACK.all = PIEACK_GROUP3;
]