Meinberg TCR LANTIME - Manual (Page 19)

The unmodulated or 'DC Level Shift' timeocdes are applied via SUB-D connector on
rear panel. Galvanic insulation of this input is obtained by an opto coupler device.
TCR510 provides two configurable serial ports ( RS232 or 1xRS485 option ), a pulse
per minute and per second ( PPS / PPM ) as well as a DCF Simulation port at TTL
Level. Further three fixed frequency outputs at 100 kHz, 1 MHz and 10 MHz at TTL
Level are available.
Function principle
After the received IRIG-Code has passed a consistency check, the software clock and
the battery backed realtime clock of TCR510 are synchronized to the external time
reference. If an error in the IRIG-telegram is detected, the boards system clock
switches into holdover mode.
Apart from the codes AFNOR NFS 87-500 and IEEE1344, IRIG-Codes do not carry
a complete date but the number of the day within the current year ( 1...366 ). Hence
the date that is output in the serial telegram must be completed by the date stored in
the buffered real time clock. The day within the current year calculated from the
RTCs date is compared with the day number from the IRIG-Code every minute.
When a mismatch between these two day numbers is detected the board signalizes
freewheeling mode, however the systems time base will continue to synchronize with
the IRIG-signal. The DCF-Simulation is surpressed in this case.
Time and date of the real time clock can be set by a Meinberg Standard Telegram via
serial port COM0. Received IRIG-time can be re-calculated into UTC provided that
no time zone changeovers such as daylight saving appear in the received IRIG-
telegrams. For more information please see chapter 'UTC-Offset' in the online
documentation of the enclosed software TCRMON.
IRIG-telegrams do not include announcers for the change of time
zone (daylight saving on/off) or for the insertion of a leap second.
Start or end of daylight saving time is executed with a delay of one
second by TCR510PCI therefore. If a leap second is inserted, the
system clock will be set to second ‘0’ for two consecutive seconds.
The board TCR510 decodes the following formats:
A133: 1000 pps, amplitude modulated sine wave signal, 10 kHz
carrier frequency
BCD time of year, SBS time of day
A132: 1000 pps, amplitude modulated sine wave signal, 10 kHz
carrier frequency
BCD time of year
A003: 1000 pps, DC Level Shift pulse width coded, no carrier
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