1: /*
   2: ***********************************************************************
   3: * Program to simulate NTP phase-lock loop                             *
   4: ***********************************************************************
   5: */
   6: #include <stdio.h>
   7: #include <ctype.h>
   8: #include <math.h>
   9: /*
  10: Parameters
  11: */
  12: #define FMAX 8                  /* max filter size */
  13: #define DAY 86400               /* one day of seconds */
  14: #define DMAX .128               /* max clock aperture */
  15: #define PI 3.1415926535         /* the real thing */
  16: /*
  17: Function declarations
  18: */
  19: extern double pow(double, double);
  20: /*
  21: Global declarations
  22: */
  23: double Kf = 1024;               /* frequency weight */
  24: double Kg = 256;                /* phase weight */
  25: double Kh = 256;                /* compliance weight */
  26: double S = 16;                  /* compliance maximum */
  27: double T = 262144;              /* compliance factor */
  28: double U = 4;                   /* adjustment interval */
  29: double poll = 64;               /* poll interval */
  30: ;
  31: double f = 0;                   /* frequency error */
  32: double g = 0;                   /* phase error */
  33: double h = 0;                   /* compliance */
  34: double c = 0;                   /* clock error */
  35: double d;                       /* current filter output */
  36: double filt[FMAX];              /* clock filter */
  37: ;
  38: double offset = .01;             /* initial phase offset */
  39: double freq = 10e-6;             /* initial frequency offset */
  40: ;
  41: double t;                       /* current time */
  42: double q, a, x, z;              /* temporaries */
  43: int ns = 0;                     /* reset counter */
  44: int n,i;                        /* integer temporary */
  45: /*
  46: Main program
  47: */
  48: main() {
  49:     n = poll/U; q = 1-1/Kg; q = ((pow(q,n)-1)/(q-1))/Kg;
  50:     ns = 0; x = 0; z = 8;
  51:         for (t = 0; t < 2*DAY; t += poll) {
  52:         for (i = FMAX-1; i > 0; i--) filt[i] = filt[i-1];
  53:         filt[0] = (offset-c-freq*t); d = filt[FMAX-1];
  54:         if (fabs(d) >= DMAX) {
  55:             ns++; c = c+d;
  56:             for (i = 0; i < FMAX; i++) filt[i] = 0;
  57:             printf("Reset %5.0f\n", d*1000);
  58:             }
  59:         a = S-T*fabs(h); if (a<1) a=1;
  60:         h = h+(d-h)/Kh;
  61:         f = f+d/(a*poll);
  62:         g = d*q; c = c+g+(poll/(U*Kf))*f;
  63: 
  64:         printf("%8.2f%8.2f%8.2f%8.2f%8.2f   %8.2e",
  65:         t/60, offset*1000, d*1000, (f/(U*Kf)+freq)*1e6,
  66:         h*1000, a);
  67:         printf("\n");
  68:         }
  69:     return (0);
  70:     }

Defined functions

main defined in line 48; never used

Defined variables

Kf defined in line 23; used 2 times
Kg defined in line 24; used 2 times
  • in line 49(2)
Kh defined in line 25; used 1 times
  • in line 60
S defined in line 26; used 1 times
  • in line 59
T defined in line 27; used 1 times
  • in line 59
U defined in line 28; used 3 times
a defined in line 42; used 5 times
c defined in line 34; used 5 times
d defined in line 35; used 8 times
f defined in line 31; used 4 times
filt defined in line 36; used 5 times
freq defined in line 39; used 2 times
g defined in line 32; used 2 times
  • in line 62(2)
h defined in line 33; used 5 times
i defined in line 44; used 9 times
n defined in line 44; used 2 times
  • in line 49(2)
ns defined in line 43; used 2 times
offset defined in line 38; used 2 times
poll defined in line 29; used 4 times
q defined in line 42; used 5 times
t defined in line 41; used 5 times
x defined in line 42; used 1 times
  • in line 50
z defined in line 42; used 1 times
  • in line 50

Defined macros

DAY defined in line 13; used 1 times
  • in line 51
DMAX defined in line 14; used 1 times
  • in line 54
FMAX defined in line 12; used 4 times
PI defined in line 15; never used
Last modified: 1989-03-31
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