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/*
* This program simulates a first-order, type-II phase-lock loop using
* actual code segments from modified kernel distributions for SunOS,
* Ultrix and OSF/1 kernels. These segments do not use any licensed code.
*/
#ifdef HAVE_CONFIG_H
# include <config.h>
#endif
#include <stdio.h>
#include <ctype.h>
#include <math.h>
#include <sys/time.h>
#ifdef HAVE_TIMEX_H
# include "timex.h"
#endif
/*
* Phase-lock loop definitions
*/
#define HZ 100 /* timer interrupt frequency (Hz) */
#define MAXPHASE 512000 /* max phase error (us) */
#define MAXFREQ 200 /* max frequency error (ppm) */
#define TAU 2 /* time constant (shift 0 - 6) */
#define POLL 16 /* interval between updates (s) */
#define MAXSEC 1200 /* max interval between updates (s) */
/*
* Function declarations
*/
void hardupdate();
void hardclock();
void second_overflow();
/*
* Kernel variables
*/
int tick; /* timer interrupt period (us) */
int fixtick; /* amortization constant (ppm) */
struct timeval timex; /* ripoff of kernel time variable */
/*
* Phase-lock loop variables
*/
int time_status = TIME_BAD; /* clock synchronization status */
long time_offset = 0; /* time adjustment (us) */
long time_constant = 0; /* pll time constant */
long time_tolerance = MAXFREQ; /* frequency tolerance (ppm) */
long time_precision = 1000000 / HZ; /* clock precision (us) */
long time_maxerror = MAXPHASE; /* maximum error (us) */
long time_esterror = MAXPHASE; /* estimated error (us) */
long time_phase = 0; /* phase offset (scaled us) */
long time_freq = 0; /* frequency offset (scaled ppm) */
long time_adj = 0; /* tick adjust (scaled 1 / HZ) */
long time_reftime = 0; /* time at last adjustment (s) */
/*
* Simulation variables
*/
double timey = 0; /* simulation time (us) */
long timez = 0; /* current error (us) */
long poll_interval = 0; /* poll counter */
/*
* Simulation test program
*/
int
main(
int argc,
char *argv[]
)
{
tick = 1000000 / HZ;
fixtick = 1000000 % HZ;
timex.tv_sec = 0;
timex.tv_usec = MAXPHASE;
time_freq = 0;
time_constant = TAU;
printf("tick %d us, fixtick %d us\n", tick, fixtick);
printf(" time offset freq _offset _freq _adj\n");
/*
* Grind the loop until ^C
*/
while (1) {
timey += (double)(1000000) / HZ;
if (timey >= 1000000)
timey -= 1000000;
hardclock();
if (timex.tv_usec >= 1000000) {
timex.tv_usec -= 1000000;
timex.tv_sec++;
second_overflow();
poll_interval++;
if (!(poll_interval % POLL)) {
timez = (long)timey - timex.tv_usec;
if (timez > 500000)
timez -= 1000000;
if (timez < -500000)
timez += 1000000;
hardupdate(timez);
printf("%10li%10li%10.2f %08lx %08lx %08lx\n",
timex.tv_sec, timez,
(double)time_freq / (1 << SHIFT_KF),
time_offset, time_freq, time_adj);
}
}
}
}
/*
* This routine simulates the ntp_adjtime() call
*
* For default SHIFT_UPDATE = 12, offset is limited to +-512 ms, the
* maximum interval between updates is 4096 s and the maximum frequency
* offset is +-31.25 ms/s.
*/
void
hardupdate(
long offset
)
{
long ltemp, mtemp;
time_offset = offset << SHIFT_UPDATE;
mtemp = timex.tv_sec - time_reftime;
time_reftime = timex.tv_sec;
if (mtemp > MAXSEC)
mtemp = 0;
/* ugly multiply should be replaced */
if (offset < 0)
time_freq -= (-offset * mtemp) >>
(time_constant + time_constant);
else
time_freq += (offset * mtemp) >>
(time_constant + time_constant);
ltemp = time_tolerance << SHIFT_KF;
if (time_freq > ltemp)
time_freq = ltemp;
else if (time_freq < -ltemp)
time_freq = -ltemp;
if (time_status == TIME_BAD)
time_status = TIME_OK;
}
/*
* This routine simulates the timer interrupt
*/
void
hardclock(void)
{
int ltemp, time_update;
time_update = tick; /* computed by adjtime() */
time_phase += time_adj;
if (time_phase < -FINEUSEC) {
ltemp = -time_phase >> SHIFT_SCALE;
time_phase += ltemp << SHIFT_SCALE;
time_update -= ltemp;
}
else if (time_phase > FINEUSEC) {
ltemp = time_phase >> SHIFT_SCALE;
time_phase -= ltemp << SHIFT_SCALE;
time_update += ltemp;
}
timex.tv_usec += time_update;
}
/*
* This routine simulates the overflow of the microsecond field
*
* With SHIFT_SCALE = 23, the maximum frequency adjustment is +-256 us
* per tick, or 25.6 ms/s at a clock frequency of 100 Hz. The time
* contribution is shifted right a minimum of two bits, while the frequency
* contribution is a right shift. Thus, overflow is prevented if the
* frequency contribution is limited to half the maximum or 15.625 ms/s.
*/
void
second_overflow(void)
{
int ltemp;
time_maxerror += time_tolerance;
if (time_offset < 0) {
ltemp = -time_offset >>
(SHIFT_KG + time_constant);
time_offset += ltemp;
time_adj = -(ltemp <<
(SHIFT_SCALE - SHIFT_HZ - SHIFT_UPDATE));
} else {
ltemp = time_offset >>
(SHIFT_KG + time_constant);
time_offset -= ltemp;
time_adj = ltemp <<
(SHIFT_SCALE - SHIFT_HZ - SHIFT_UPDATE);
}
if (time_freq < 0)
time_adj -= -time_freq >> (SHIFT_KF + SHIFT_HZ - SHIFT_SCALE);
else
time_adj += time_freq >> (SHIFT_KF + SHIFT_HZ - SHIFT_SCALE);
time_adj += fixtick << (SHIFT_SCALE - SHIFT_HZ);
/* ugly divide should be replaced */
if (timex.tv_sec % 86400 == 0) {
switch (time_status) {
case TIME_INS:
timex.tv_sec--; /* !! */
time_status = TIME_OOP;
break;
case TIME_DEL:
timex.tv_sec++;
time_status = TIME_OK;
break;
case TIME_OOP:
time_status = TIME_OK;
break;
}
}
}