Meinberg TCR511 - Manual (Page 9)

9
Function principle
After the received IRIG code has passed a consistency check, the software clock and
the battery backed real time clock of TCR511 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 suppressed 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 don’t include announcers for the change of time
zone (daylight saving on/off) or for the insertion of a leap second.
Hence the clock will switch into freewheeling mode in case of such
event, and resynchronize afterwards.
The board TCR511 decodes the following formats:
A133: 1000pps, amplitude modulated sine wave signal, 10 kHz carrier frequency
BCD time of year, SBS time of day
A132: 1000pps, amplitude modulated sine wave signal, 10 kHz carrier frequency
BCD time of year
A003: 1000pps, DC Level Shift pulse width coded, no carrier
BCD time of year, SBS time of day
A002: 1000pps, DC Level Shift pulse width coded, no carrier
BCD time of year
B123: 100pps, amplitude modulated sine wave signal, 1 kHz carrier frequency
BCD time of year, SBS time of day
B122: 100pps, amplitude modulated sine wave signal, 1 kHz carrier frequency
BCD time of year
B003: 100pps,DC Level Shift pulse width coded, no carrier
BCD time of year, SBS time of day
B002: 100pps, DC Level Shift pulse width coded, no carrier
BCD time of year
AFNOR NFS 87-500:100pps, amplitude modulated sine wave signal, 1 kHz carrier frequency
BCD time of year, complete date, SBS time of day