available it will switch to the next reference source of the priority order - in this case the IRIG input with an
precision of 10us. With the formula ((10000ns/100ns)*11.4) we get hold over time of 19min. The online display
of the MRS status will show the remaining time and the calculated time. The hold over time will be recalculated
if the status of the reference clocks will change.
The internal NTP is not requesting the external reference clocks directly. It will see only the internal clock of
the MRS system with its high precision oscillator OCXO. The controlling of the internal OCXO will be done
by the GNSS/MRS module. All offsets from the internal reference time to the external reference clocks will be
send to the GNSS/MRS clock. The external NTP server will be configured as "server" at the internal NTP with
the option "noselect" only to get the offsets to the external NTP servers.
The status information of the activated reference clocks will be shown in the display. The state of the master
will be marked with "*" or written as text. Also the offset from the reference clock to the internal clock will be
displayed.
1.GPS * 20ns 2.PPS 30ns
2.NTP 30.000us
1.GPS is master : -10ns
2.PPS in is available : -20ns
3.IRIG no signal : n/a
4.NTP is available : -30.000us
2.PTP(IEEE1588)is available : -300ns
F1
MRS Input Priorities
1.GPS * 20ns
2.PPS 30ns
3.NTP 30.000us
M300: LC-Display 40 x 2 Characters
M400 / M900: LC-display, 4 x 16 Characters
M600: Vacuum fluorescent graphic display (VFD), 256 x 64 dots
If an external PTP IEEE1588 grandmaster is available the reference source will be taken prior to the external
NTP server. The PTP time stamping unit will be scanned every 10 seconds (independently of the broadcast
interval of the PTP master). The external NTP server will be scanned every 64 seconds.
After setting the time offset of the internal clock module the NTP will be restarted. Now only small offset
values will be sent to the internal clock module; the fine synchronization mode will start. In the "fine synchro-
nization mode" all offsets greater than 10 ms will be ignored 5 times in a row - after the 5 times the offset will
be set.
IMPORTANT:
After power up the Lantime/MRS the maximum time difference between internal clock and
external NTP server or PTP grandmaster must be lower than 1000s. Otherwise the internal clock must be set
manually via LC-Display or synchronized by GNSS reference once.
38
Date: 16th February 2021
LANTIME
Summary of Contents for LANTIME M300/MRS/AD10-AD10
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