Meinberg LANTIME IMS-M500, Руководство пользователя

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7 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. This guarantees that the file
system is in a defined condition after restart. This boot process takes approximately two minutes. During this
time the following message appears on the display:
NORMAL OPERATION
NTP: not sync
Thu, 01.01.2008
UTC 12:00:00 NORMAL OPERATION
NTP:sync to local
Thu, 01.01.2008
UTC 12:00:00
After starting the LINUX system, the network function is initiated and the communication program with the
receiver and the NTPD (NTP daemon) is started. Then NTPD starts synchronization with the reference clocks
(usually the hardware clock of the single board computer and the integrated receiver clock). The message "NTP:
sync to local" is displayed until synchronization is complete.
For the synchronization of the NTPD with the time reference it is necessary that the receiver is synchronous
with the incoming time signal. In this case the following message is monitored on the display:
NORMAL OPERATION
NTP: Offs. 2ms
Thu, 01.01.2008
UTC 12:00:00
The second line shows the user that the NTPD is synchronized with the receiver with an offset of 2ms (Figure).
Because of the internal time of the NTP which is adjusted by a software PLL (phase locked loop) it takes a
certain time to optimise 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 receiver’s time. Typically values for the offset are +-5 ms after the
NTPD has already synchronized.
16 Date: 9th June 2016 LANTIME IMS-M500