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DXD/PTP/GPS User Manual (rev 2.10)
7. DXD/OCXO
The DXD/OCXO is an optional Oven-Controlled Crystal Oscillator for the DXD series. It achieves a very high frequency
stability providing greater long-term time and TOD accuracy (+/-10ppb, equivalent to less than +/-10 frames per year). The
DXD/OCXO is particularly recommended when using the DXD/GPS option as the greater stability of the OCXO will minimize
drift during long GPS dropouts.
After installing the OCXO, no special setting is required. The DXD will automatically use the OCXO as the Internal oscillator
and indicate INTERNAL/OCXO on the different displays.
Installation is very simple and does not require any soldering. For instructions, see Appendix B at the end of this manual.
8. Time of Day
Time of Day is an essential part of the DXD-8 design. In a PTP network, the devices all need to know the Time of Day, i.e. year,
month, day, hour and seconds, even nanoseconds, to achieve frequency and phase synchronization. At the heart of the DXD-8
is the Main Time of Day Clock (TOD) & Reference Frame Generator. This is where System Time is generated and where the
references generated by the DXD-8 are aligned with the PTP epoch.
BNC IN A
WC
AES
VID
10MHz
BNC IN B
WC
AES
VID
10MHz
INT
TCXO
ETHERNET
PTP
ANT
GPS
INT
OCXO
INT
RTC
ETHERNET
NTP
ETHERNET
PTP
ANT
GPS
As shown on the diagram above, some of the reference sources include time and rate information. GPS and PTP for example
carry precise time and date information as well as frequency. However, traditional reference signals, such as video sync or
word clock, only carry the frequency information. When selecting one of those as reference (BNC inputs), the time information
needs to be added from another source. The DXD-8 offers several options.
When using a reference without date & time information such as video sync, there will be a date & time adjustment in
the TOD count so that video frame edges are correctly aligned. The internal TOD is always creating internal
frame references that are aligned as required with Jan 1, 1970 (PTP epoch). To lock to an external
frame edge the DXD has to move the TOD count by up to +/- half a frame to synchronize the internal TOD frame
edge to the incoming edge.
REFERENCE SOURCES
(RATE)
REFERENCE
SELECT
(
BMCA
)
TIME SOURCES
(POSITION)
TIME
SELECT
(
BMCA
)
DXD-8 DIAGRAM
SYNC
INTERNAL
TIME OF DAY
CLOCK
&
REFERENCE
FRAME
GENERATOR
SYNC
IMPORTANT NOTE
UNIVERSAL OUTPUTS
BNC OUT 1 & 2
• WC
• 10 MHz
SYNC
• AES
• 1PPS
• VID
BNC OUT 3 & 4
• WC
• 10 MHz
SYNC
• AES
• 1PPS
• VID
BNC OUT 5 & 6
• WC
• 10 MHz
SYNC
• AES
• 1PPS
• VID
BNC OUT 7 & 8
• WC
• 10 MHz
SYNC
• AES
• 1PPS
• VID
PTP
ETHERNET
IEEE-1588
Rate & Position
Rate Only
Position Only
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