2  * This program simulates a first-order, type-II phase-lock loop using
21  * Phase-lock loop definitions
24 #define MAXPHASE 512000		/* max phase error (us) */
26 #define TAU 2			/* time constant (shift 0 - 6) */
45  * Phase-lock loop variables
54 long time_phase = 0;		/* phase offset (scaled us) */
62 double timey = 0;		/* simulation time (us) */
88 		timey += (double)(1000000) / HZ;  in main()
90 		    timey -= 1000000;  in main()
93 			timex.tv_usec -= 1000000;  in main()
98 				timez = (long)timey - timex.tv_usec;  in main()
100 				    timez -= 1000000;  in main()
101 				if (timez < -500000)  in main()
106 				       (double)time_freq / (1 << SHIFT_KF),  in main()
116  * For default SHIFT_UPDATE = 12, offset is limited to +-512 ms, the
118  * offset is +-31.25 ms/s.
128 	mtemp = timex.tv_sec - time_reftime;  in hardupdate()
135 	    time_freq -= (-offset * mtemp) >>  in hardupdate()
143 	else if (time_freq < -ltemp)  in hardupdate()
144 	    time_freq = -ltemp;  in hardupdate()
159 	if (time_phase < -FINEUSEC) {  in hardclock()
160 		ltemp = -time_phase >> SHIFT_SCALE;  in hardclock()
162 		time_update -= ltemp;  in hardclock()
166 		time_phase -= ltemp << SHIFT_SCALE;  in hardclock()
175  * With SHIFT_SCALE = 23, the maximum frequency adjustment is +-256 us
188 		ltemp = -time_offset >>  in second_overflow()
191 		time_adj = -(ltemp <<  in second_overflow()
192 			     (SHIFT_SCALE - SHIFT_HZ - SHIFT_UPDATE));  in second_overflow()
196 		time_offset -= ltemp;  in second_overflow()
198 			(SHIFT_SCALE - SHIFT_HZ - SHIFT_UPDATE);  in second_overflow()
201 	    time_adj -= -time_freq >> (SHIFT_KF + SHIFT_HZ - SHIFT_SCALE);  in second_overflow()
203 	    time_adj += time_freq >> (SHIFT_KF + SHIFT_HZ - SHIFT_SCALE);  in second_overflow()
204 	time_adj += fixtick << (SHIFT_SCALE - SHIFT_HZ);  in second_overflow()
211 			timex.tv_sec--; /* !! */  in second_overflow()