有一段VX的延迟代码，看不懂为什么这样写，有什么好处？

/******************************************************************************

  FUNCtiON:                ADT_L0_msSleep

*****************************************************************************/

/*! brief Waits for the requested number of milliseconds

*

* This function waits for the requested number of milliseconds.

*

* @param msDelay is the number of milliseconds to wait.

*/

void ADT_L0_CALL_CONV ADT_L0_msSleep(ADT_L0_UINT32 msDelay)

{

        static int delayLoop = 0;

        int ix;

        int iy;

        int maxLoop;

        int start;

        int stop;

        int mpt; /* microsecs per tick */

        msDelay = msDelay*1000; /* Convert input to usec*/

        if (delayLoop == 0 || msDelay == 0xffffffff) /* need calibration? Run first time only when delayLoop=0 */

        {

                start = 0;

                stop = 0;

                mpt = (1000 * 1000) / sysClkRateGet (); /* microsecs per tick */

   

                for (delayLoop = 1; delayLoop < 0x1000 && stop == start; delayLoop<<=1)

                {

                        for (stop = start = tickGet (); start == stop; start = tickGet ())

                                ; /* wait for clock turn over */

   

                        ADT_L0_msSleep(mpt/1000); /* single recursion */

                        stop = tickGet ();

                }

                maxLoop = delayLoop / 2; /* loop above overshoots */

                start = 0;

                stop = 0;

                if (delayLoop < 4)

                        delayLoop = 4;

   

                for (delayLoop /= 4; delayLoop

                {

                        for (stop = start = tickGet (); start == stop; start = tickGet ())

                                ; /* wait for clock turn over */

   

                        ADT_L0_msSleep(mpt/1000); /* single recursion */

                        stop = tickGet ();

                }

        }

        /* Main delay loop after calibration above*/

        for (iy = 0; iy < msDelay; iy++)

        {

                for (ix = 0; ix < delayLoop; ix++);

        }

}