/* delayLib.c - self-calibrating hard delay routines *//*modification history--------------------27Mar96,espin written.$Id: delayLib.c,v 1.2 1999/10/25 18:22:05 borkhuis Exp $*//*DESCRIPTIONThis module provides "hard" [<]delay[>] routines for micro andmillisecondperiods.EXAMPLE.CS-> delayMsec (1); /@ very first call used for calibration @/-> timexN delayMsec, 10timex: 75 reps, time per rep = 9555 +/- 222 (2%) microsecsvalue = 59 = 0x3b = ';'->.CEThe routines sysClkRateGet() and tickGet() are used to calibratethe timing loop the first time either routine is called. Therefore,the first call is much longer than requested. If the system clockrate is changed, a new calibration must be explicitly made bypassing a negative [<]delay[>] duration.INTERNALA one-shot timer could provide high resolution sub-clock tickdelay... but then this would be board dependent.*/#include "vxWorks.h"#include "tickLib.h"#include "sysLib.h"#define DEBUG FALSEvoid delayUsec (unsigned int u);void delayMsec (unsigned int m);/******************************************************************************* * * delayUsec - hard [<]delay[>] for <u> microseconds * * Parameters : int u = nr of microsecs to wait before returning. * * RETURNS: N/A */#if DEBUGint delayLoop = 0;#endif /* DEBUG */voiddelayUsec ( unsigned int u ){    #if !DEBUG    static int delayLoop = 0;    #endif /* !DEBUG */    int ix;    int iy;       if (delayLoop == 0 || u == 0xffffffff)      /* need calibration?          */    {        int maxLoop;        int start = 0;        int stop = 0;        int mpt = (1000 * 1000) / sysClkRateGet (); /* microsecs per tick     */              for (delayLoop = 1; delayLoop < 0x1000 && stop == start; delayLoop<<=1)        {            /* wait for clock turn over */            for (stop = start = tickGet (); start == stop; start = tickGet ());                     delayUsec (mpt);            /* single recursion                   */            stop = tickGet ();        }              maxLoop = delayLoop / 2;        /* loop above overshoots              */        #if DEBUG        printf ("maxLoop = %d\n", maxLoop);        #endif /* DEBUG */        start = 0;        stop = 0;        if (delayLoop < 4)            delayLoop = 4;        for (delayLoop /= 4; delayLoop<maxLoop && stop == start; delayLoop++)        {            /* wait for clock turn over */            for (stop = start = tickGet (); start == stop; start = tickGet ());                     delayUsec (mpt);            /* single recursion                   */            stop = tickGet ();        }        #if DEBUG        printf ("delayLoop = %d\n", delayLoop);        #endif /* DEBUG */    }       for (iy = 0; iy < u; iy++)    {        for (ix = 0; ix < delayLoop; ix++);    }}/******************************************************************************* * * delayMsec - hard [<]delay[>] for <m> milliseconds * * Parameters : int u = nr of millisecs to wait before returning. * * RETURNS: N/A */voiddelayMsec ( unsigned int m){    delayUsec (m * 1000);}