DSP2812例程BLDC3-1的一个疑惑

// ***************** LEVEL3 *****************
#if (BUILDLEVEL==LEVEL3)

// ------------------------------------------------------------------------------
//    Call the ADC04U_DRV read function.
// ------------------------------------------------------------------------------
   adc1.read(&adc1);

// ------------------------------------------------------------------------------
//    Connect inputs of the RMP module and call the Ramp control
//    calculation function.
// ------------------------------------------------------------------------------
      rc1.TargetValue = _IQ(SpeedRef);
      rc1.calc(&rc1);

// ------------------------------------------------------------------------------
//    Connect inputs of the HALL module and call the Hall sensor
//    read function.
// ------------------------------------------------------------------------------
      hall1.HallMapPointer = (int16)mod1.Counter;
      hall1.read(&hall1);

// ------------------------------------------------------------------------------
//    Connect inputs of the MOD6 module and call the Modulo 6 counter
//    calculation function.
// ------------------------------------------------------------------------------
      mod1.TrigInput =(int32)hall1.CmtnTrigHall;
      mod1.Counter = (int32)hall1.HallMapPointer;
      mod1.calc(&mod1);

// ------------------------------------------------------------------------------
//    Connect inputs of the RMP2 module and call the Ramp control 2
//    calculation function.
// ------------------------------------------------------------------------------
      rmp2.DesiredInput = (int32)DFuncDesired;
      rmp2.calc(&rmp2);

// ------------------------------------------------------------------------------
//    Connect inputs of the PID_REG3 module and call the PID speed controller
//    calculation function.
// ------------------------------------------------------------------------------ 
      pid1_spd.Ref = rc1.SetpointValue;
      pid1_spd.Fdb = speed1.Speed;
      pid1_spd.calc(&pid1_spd);

// ------------------------------------------------------------------------------
//    Set the speed closed loop flag once the speed is built up to a desired value.
// ------------------------------------------------------------------------------
      if (rc1.EqualFlag == 0x7FFFFFFF)  {
         SpeedLoopFlag = TRUE;
         rc1.RampDelayMax = 300; 
      }

// ------------------------------------------------------------------------------
//    Connect inputs of the PWM_DRV module and call the PWM signal generation
//    update function.
// ------------------------------------------------------------------------------
   // Switch from fixed duty-cycle or controlled Speed duty-cycle by SpeedLoopFlag variable
      if (SpeedLoopFlag == FALSE)
         pwm1.DutyFunc = (int16)rmp2.Out;           // fixed duty-cycle
      else
         pwm1.DutyFunc = (int16)_IQtoIQ15(pid1_spd.Out);   // controlled Speed duty-cycle

      pwm1.CmtnPointer = (int16)mod1.Counter;
      pwm1.update(&pwm1);

// ------------------------------------------------------------------------------
//    Connect inputs of the SPEED_PR module and call the speed calculation
//    function.
// ------------------------------------------------------------------------------ 
      if ((mod1.Counter == 5)&(hall1.CmtnTrigHall == 0x7FFF)) {
         speed1.TimeStamp = VirtualTimer;
         speed1.calc(speed1);
      }

// ------------------------------------------------------------------------------
//    Connect inputs of the DATALOG module
// ------------------------------------------------------------------------------
      DlogCh1 = (int16)mod1.Counter;
      DlogCh2 = (int16)mod1.TrigInput;
      DlogCh3 = (int16)_IQtoIQ15(pid1_spd.Ref);
      DlogCh4 = (int16)_IQtoIQ15(pid1_spd.Fdb);

// ------------------------------------------------------------------------------
//    Connect inputs of the EN_DRV module and call the enable/disable PWM signal
//    update function (for DMC1500 only).
// ------------------------------------------------------------------------------   
      drv1.EnableFlag = EnableFlag;
      drv1.update(&drv1);

#endif // (BUILDLEVEL==LEVEL3)

// ------------------------------------------------------------------------------
//    Increase virtual timer and force 15 bit wrap around
// ------------------------------------------------------------------------------
 VirtualTimer++;
 VirtualTimer &= 0x00007FFF;

// ------------------------------------------------------------------------------
//    Call the DATALOG update function.
// ------------------------------------------------------------------------------
    dlog.update(&dlog);

#if (DSP_TARGET==F2808)
// Acknowledge interrupt to recieve more interrupts from PIE group 1
 PieCtrlRegs.PIEACK.all = PIEACK_GROUP1;
#endif

#if (DSP_TARGET==F2812)
// Enable more interrupts from this timer
 EvaRegs.EVAIMRB.bit.T2PINT = 1;
 
// Note: To be safe, use a mask value to write to the entire
 // EVAIFRB register.  Writing to one bit will cause a read-modify-write
 // operation that may have the result of writing 1's to clear
 // bits other then those intended.
    EvaRegs.EVAIFRB.all = BIT0;*************************************就是这句********************************
 
// Acknowledge interrupt to recieve more interrupts from PIE group 3
 PieCtrlRegs.PIEACK.all |= PIEACK_GROUP3;
#endif
}

您好，感谢您的回答，我有疑问的那句就在这段的倒数第6行