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SLM-3650 Satellite Modem
Operation
3.4.3
Function Select: Configuration: Interface
Refer to Figure 3-6.
TX CLOCK SOURCE
TX CLOCK PHASE
EXT-CLK FREQ
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Programs the clock source for the modem transmitter clock to the following configurations:
TX TERRESTRIAL: Sets the TX clock to recover timing from the incoming clock/data.
SCT (INTERNAL): Sets the TX clock to operate from the modem internal clock (this is also
the fallback clock).
Note: When loop timing is enabled, SCT (LOOP) is displayed instead of SCT (INTERNAL).
EXT. CLOCK/DATA CLOCK: Sets the TX clock to operate from the external reference clock.
Ext Clock: TX Data Rate and Ext. Clock frequency shall match or ASLT option. The correct
frequency must be programmed into EXT-CLK FREQ.
Upon entry, the current transmit clock setting is displayed. Press [↑] or [↓] to make the
selection. Press [ENTER] to execute the change.
Programs the TX clock phase to AUTO, NORMAL, or INVERT.
Upon entry, the current setting of the TX clock phase is displayed. Press [↑] or [↓] to make
the selection. When AUTO is selected, the modem will automatically select NORMAL or
INVERT to properly phase the TX clock with the TX data. Press [ENTER] to execute the
change.
Programs the external reference clock input frequency between 8.0 kHz and 10.0 MHz.
Notes:
The clock rate must be equal to the data rate unless the asymmetrical loop timing
option is present.
When an ODU or BUC is operated with an EXT REF, 10MHz is required.
This clock frequency can be any multiple of 600 Hz from 2.4 to 64 kHz, and can be any
multiple of 8 kHz from 64 kHz to 4.376 MHz. This can be used for the Doppler/plesiochronous
buffer reference. It can be a reference to SCT.
Use the master clock input on J8 for the external master reference. The EXT REF on CP3
only allows for 1, 5, 10, and 20 MHz EXT REF input.
Upon entry, the current setting for the external reference is displayed. Press [←] or [→] to
increment or decrement the digit at the flashing cursor. Press [ENTER] to execute the
change.
3–18
Revision 3
MN/SLM3650.IOM
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