TrueTime VME-SG2 560-5608, Manual

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5
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m
m
a
a
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d
d
o
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Rev. F
d. DYNAMIC - The Dynamic mode is used when the unit is moving at
velocities up to 1000 knots. The GPS Receiver can determine 3 dimensional
position (Latitude, Longitude and Elevation) when 4 or more satellites are in
view. When only 3 satellites are available the last elevation value computed will
be held fixed and the unit will compute 2 dimensional position. Time lock is not
possible if less than 3 satellites are available.
LOCAL OFFSET (base a hex 00A6)
This register allows for the output of local time from the VME-SG-GPS. This parameter
is used in the GPS synchronized generator mode only to convert the time received from
the GPS Engine time reference to local time. The Local Offset is any value b
12 and - 12 hours. The following describes the Local Offset word:
RATE OUTPUT SELECTION (hex 00A8)
This parameter controls the Pulse Rate generation logic. The Pulse Rate output is
available at the P2/J2 connector pin C2. Five different Pulse Rates are available as
described in the table below. The rising edge of the pulse rate output is active and "on
time". The duty cycles for the different rate outputs are specified in section one.
The Pulse Rate output can also generate VME interrupts. For more information about
the Rate Generation INT1 interrupt see section 2.4.10.
Character RATE
0 - Pulse Rate Disabled
1 - 10,000 Pulses Per Second (PPS)
2 - 1000 PPS
3 - 100 PPS
4 - 10 PPS
5 - 1 PPS
OSCILLATOR CONTROL VOLTAGE SETTING (hex 00AA)
The Oscillator Control Voltage Setting is a 16 bit hexadecimal value that indicates the
current output from the frequency control digital to analog (DAC) converter. The DAC
output controls the frequency of the crystal oscillator that is the time base for all
generator/sync-generator operations. This output will range between 0 and hex FFFF.
In the GPS sync-gen mode after the card has attained phase lock, a midrange DAC
value of about hex 7FFF + 1000 is normal. With aging the oscillator DAC setting will
change to maintain good oscillator discipline. If DAC settings near 0 or hex FFFF are
observed this indicates that either a failure has occurred or the oscillator needs to be
recalibrated.
In the Code Sync-gen modes this value may vary from its midrange value significantly
depending on the frequency accuracy and stability of the generator that is providing the
IRIG B reference code.
Data Bits
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
+/- Sign (ASCII) Tens Hours Unit Hours
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