+/*
+ * The following defines are used only if a pulse-per-second (PPS)
+ * signal is available and connected via a modem control lead, such as
+ * produced by the optional ppsclock feature incorporated in the Sun
+ * asynch driver. They establish the design parameters of the frequency-
+ * lock loop used to discipline the CPU clock oscillator to the PPS
+ * signal.
+ *
+ * PPS_AVG is the averaging factor for the frequency loop, as well as
+ * the time and frequency dispersion.
+ *
+ * PPS_SHIFT and PPS_SHIFTMAX specify the minimum and maximum
+ * calibration intervals, respectively, in seconds as a power of two.
+ *
+ * PPS_VALID is the maximum interval before the PPS signal is considered
+ * invalid and protocol updates used directly instead.
+ *
+ * MAXGLITCH is the maximum interval before a time offset of more than
+ * MAXTIME is believed.
+ */
+#define PPS_AVG 2 /* pps averaging constant (shift) */
+#define PPS_SHIFT 2 /* min interval duration (s) (shift) */
+#define PPS_SHIFTMAX 8 /* max interval duration (s) (shift) */
+#define PPS_VALID 120 /* pps signal watchdog max (s) */
+#define MAXGLITCH 30 /* pps signal glitch max (s) */
+