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Functional description – Meinberg TCR511PEX User Manual

Page 9

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9

Functional description

After the received IRIG code has passed a consistency check, the software clock and

the battery backed realtime clock of TCR511PEX are synchronized to the external time
reference. If an error in the IRIG telegram is detected, the system clock of the board
switches to holdover mode. Drifting of the internal time base and the generated pulses
(PPS/PPM) is limited to 1

µsec/sec by regulating the onboard quartz of TCR511PEX.

IRIG code includes day of year information only. The complete date is kept in the battery
backed realtime clock and the software clock therefore. The received day of year is
compared to this complete date once per minute. If the board detects a difference
between received and stored date information, TCR511PEX switches to holdover mode
but still synchronizes the internal time base to the received IRIG code.

Date and time kept in the realtime clock can be set by sending a Meinberg Standard

Time Telegram to the serial interface COM0 or via the PCI-Express bus.

The internal system clock is always set to the received IRIG time,
which might have a local offset to UTC. Only if TCR511PEX is
configured with this offset, Meinberg driver software is able to set
the system time of the computer correctly.
The serial interface COM0
can send the Standard Meinberg Timestring with UTC or local (IRIG)
time.

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 TCR511PEX 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