Microchip LN-CSAC-SA65 handleiding
Handleiding
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LN-CSAC Model SA65-LN User’s Guide
2024 Microchip Technology Inc. and its subsidiaries DS50003805A-page 23
Prior to the onset of steering, the disciplining algorithms first perform an initialization
sequence in which the variables of the steering algorithm are reset to defaults and a
1 PPS synchronization operation (see Section 3.3.4 “1 PPS Synchronization (S)”) is
executed to bring the 1 PPS output within 100 ns of the reference.
Initialization is performed when Disciplining is first enabled in the mode register and, in
the case where Disciplining is already enabled after the LN-CSAC achieves frequency
lock (BITE = 0, status = 0).
Automatic synchronization, at ±100 ns, is enabled along with Disciplining, in order to
maintain PPSOUT – PPSEXT < ±100 ns. This may happen, for example, during the
early stages of disciplining, particularly if the initial frequency or phase of PPSOUT is
far from that of PPSEXT.
In the event that the 1 PPS reference is removed from pin 9 while Disciplining, the
LN-CSAC remains in holdover and preserves the most recent steering value. If the
1 PPS reference subsequently reappears, Disciplining continues where it left off, with-
out reinitializing.
If it is necessary to force re-initialization of the disciplining variables, perhaps because
the reference source is deemed untrustworthy and subsequently recovers, this can be
accomplished by disabling and re-enabling Disciplining in the mode register (see
Section 3.3.3 “Set/Clear Operating Modes (M)”).
In Clockstudio, enabling/disabling Disciplining and setting the discipline time constant
are both accomplished on the 1 PPS panel, accessible from the View menu (See
Figure 2-5 modify the discipline time constant, enter the new value in the field (60 to
10000 in seconds) and click Apply Changes.
The status of Disciplining is indicated by the DiscOK parameter in the telemetry.
DiscOK = 0 upon startup. DiscOK = 1 when magnitude of TIC measurement is less than
a user-specified threshold (see Section 3.3.9 “Set Threshold for DiscOK Indicator
(m)”) for two time constants of duration. DiscOK = 2 when in holdover (disciplining
enabled but no 1 PPS present).
The DiscOK indicator and DiscOKthreshold have no impact on the behavior or perfor-
mance of the LN-CSAC, DiscOK is a simple status indicator. In practice, DiscOK is fre-
quently employed for detection of initial acquisition to an external reference. It is less
useful for long-term monitoring, where intermediate excursions may exceed the
long-term stability objective.
In Clockstudio, the current status of DiscOK and the DiscOKthreshold setting both
appear on the 1 PPS tab (See Figure 2-5). To modify DiscOKthreshold, enter the new
value (10 to 10000 in nanoseconds) in the field and click Apply Changes.
Note: Due to the time it takes for the internal loop filter (see Figure 2-1) to adjust
the crystal frequency, it is recommended to use longer time constants if the
application allows. Shortening the time constant may cause unwanted
overshoot or frequency oscillation while disciplining.
Note: Automatic Synchronization mode (see Section 2.9.2 “Automatic Syn-
chronization”) and Disciplining mode are mutually exclusive. Enabling
either in the mode register disables the other.
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Productinformatie
| Merk | Microchip |
| Model | LN-CSAC-SA65 |
| Categorie | Niet gecategoriseerd |
| Taal | Nederlands |
| Grootte | 6392 MB |
