CC2480 halDelay()

I'm not know MSP430 hardware very well.  The function halDelay() put me in difficult position.Who can give a detail description ,thanks!

void halDelay(uint8 msecs, uint8 sleep)
{
  // Expected scaling for msecs is 3/2, but depends on result of TimerA calibration.
  // TBD - not enough code space: uint16 stop = msecs * (TACCR0_INIT / 10) / (1000 / 10);
  uint16 stop = msecs * 3 / 2;

  HAL_DISABLE_INTERRUPTS();
  TACTL &= ~MC_1;  // Stop the timer.

  if (TAR != TACCR0_INIT)
  {
    stop += TAR;
    if (stop == TACCR0_INIT)
    {
      stop++;
    }
  }
  TACCR0 = stop;

  TACTL |= MC_1;  // Re-start the timer.
  HAL_ENABLE_INTERRUPTS();

  if (sleep)
  {
    do {
      HAL_LOW_POWER_MODE();
    } while (TACCR0 != TACCR0_INIT);
  }
}