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DXD/GPS/OCXO User Manual (rev 2.10)
7. Time of Day
Time of Day is an essential part of the DXD 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
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 are aligned with the PTP epoch.
As shown on the diagram above, some of the reference sources include time and rate information (green color). 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 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.
7.1 RTC (REAL TIME CLOCK)
A backup clock, called the RTC (Real Time Clock) is included in the DXD. It is set at the factory (date & time) and runs
continuously, even when the unit is turned off as it is powered by an internal battery.
The DXD uses the date & time information from the RTC just after power up and transfers it to
the main TOD (System Time). When locking to a new reference, if that reference does not
have date & time, the TOD simply continues counting along its current time sequence; if it has
date & time, that information is transferred to the TOD.
Although the RTC is set at the factory, it can also be set manually by the operator.
Auto Update RT Clock
With the DXD/GPS installed, the RTC can be updated automatically (menu 7.2).
RATE
(REFERENCE SOURCES)
BNC IN A
WC
AES
A
VID
10MHz
BNC
INPUTS
BNC IN B
WC
AES
B
VID
10MHz
INT
REFERENCE
TCXO
SELECT
INT
OCXO
ETHERNET
PTP
ANT
GNSS
ETHERNET
P1
P2
POSITION
P3
(TIME SOURCES)
P4
INT
RTC
ETHERNET
PTP
ETHERNET
ANT
TIME
NTP
SELECT
ANT
GNSS
BNC/SDI
SDI
Time Code
Rate & Position
Rate Only
Position Only
DXD-16 DIAGRAM
SYNC
SYNC
SYNC
SYNC
INTERNAL
TIME OF DAY
SYNC
CLOCK
&
SYNC
REFERENCE
FRAME
SYNC
GENERATOR
SYNC
SYNC
IMPORTANT NOTE
Page 7
UNIVERSAL OUTPUTS
BNC OUT 1- 4
1
• WC
• 10 MHz
2
• AES
• 1PPS
3
• VID
4
BNC OUT 5 - 8
5
• WC
• 10 MHz
6
• AES
• 1PPS
7
• VID
8
BNC OUT 9&10
• WC
• 10 MHz
9
• AES
• 1PPS
10
• VID
BNC OUT 11&12
• WC
• 10 MHz
11
• AES
• 1PPS
12
• VID
BNC OUT 13&14
• WC
• 10 MHz
13
• AES
• 1PPS
14
• VID
BNC OUT 15&16
• WC
• 10 MHz
15
• AES
• 1PPS
16
• VID
TIME CODE (option)
DB25
TC1
TC 1
TC 2
TC2
ETHERNET
Port 1
PTP
Port 2
PTP
Port 3
PTP
Port 4
PTP
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