Booting the Single Board Computer
The LINUX operating system is loaded from a packed file on the flash disk of the
single board computer to a RAM disk. All files of the flash disk are stored in the
RAM disk after booting. Because of that it is guaranteed that the file system is in a
defined condition after restart. This boot process takes approx. two minutes. During
this time the following message appears on the display:
Starting up
Please wait. . .
. . . .
After starting up the LINUX system the network function is initiated and the program
for communication with the GPS and the NTPD (NTP daemon) is started. After that
NTPD starts synchronization with the reference clocks (usual the hardware clock of
the single board computer and the GPS and PZF receiver). Until synchronization is
finished the following message is displayed:
GPS:ASY PZF:SYN
NTP:SYN REF:PZF
Thu, 01.01.2008
UTC 12:00:00
The NTPD will try to synchronize either to GPS or to PZF receiver redundantly. For
the synchronization of the NTPD with the GPS it is necessary that the GPS receiver is
synchronous with the GPS time. In this case the following message is monitored on
the display:
GPS:SYN PZF:ASY
NTP:SYN REF:GPS
Thu, 01.01.2008
UTC 12:00:00
he second line shows the user that the NTPD is synchronized with the GPS. Because
of the internal time of the NTP which is adjusted by a software PLL (phase locked
loop) it takes a certain time to optimize this offset. The NTPD tries to keep the offset
below ±128 ms; if the offset becomes too large the system time is set with the
reference time. Typically values for the offset are +-5 ms after the NTPD has already
synchronized.
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Содержание M900
Страница 1: ...Technical Information Operating Instructions M900 GPS PZF Redundant SHS ...
Страница 21: ...Assembly with CN UB E 21 ...
Страница 48: ...48 ...
Страница 64: ...Configuration Ethernet 64 ...
Страница 69: ...Configuration Notification 69 ...
Страница 74: ...Configuration Security 74 ...
Страница 87: ...Configuration Local 87 ...
Страница 95: ...Configuration Statistics 95 ...
Страница 144: ...IRIG Standard Format 144 ...
Страница 145: ...AFNOR Standard Format 145 ...