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SDM-300A Satellite Modem
BUFFER CLOCK
BUFFER SIZE
BUFFER CENTER
RX CLOCK PHASE
Rev. 4
Programs the interface buffer output clock to one of the following
modes:
•
RX (SATELLITE): Sets the output buffer clock to the satellite
clock. (This is a Bypass.)
•
SCT (INTERNAL): Sets the buffer clock to operate from the
modem internal clock. This is also the fallback clock.
•
EXT. CLOCK: Sets this clock source to the external clock.
•
TX TERRESTRIAL: Sets the buffer output clock to recover
timing from the incoming TX data clock.
•
INSERT CLOCK: Selects the recovered clock from the insert
send data input received from the terrestrial equipment.
Upon entry, the current setting of the plesiochronous buffer clock is
displayed. Press [↑] or [↓] to make the selection. Press [ENTER] to
execute the change.
Sets the size of the buffer.
Upon entry, the current buffer length is displayed. Press [↑] or [↓] to
select the desired buffer size. The buffer size is displayed in seconds or
bits. Enter the Utility Interface menu to change the buffer units to
seconds or bits. If selecting seconds, choose from 1 to 99 ms, in
increments of 1 ms or 0 (Bypass). If selecting bits, choose from 32 to
262144 bits, in increments of 16 bits. Press [ENTER] to execute the
change.
When D&I is selected for modem type, the buffer units are
automatically set to ms. The user may select as follows:
•
nn = 7.5, 15, or 30 ms for E1CAS format.
•
nn = 6, 12, 24, or 30 ms for T1IBS/T1S/T1ESFS format.
•
nn = 1, 2, 4, 8, 16, or 32 ms for all other D&I formats.
Note: To have the modem calculate the plesiochronous shift, set the
buffer units to ms. When a specific buffer depth is desired, set the
buffer units to bits. Select bits or ms from the Utility Interface menu.
This configuration function is used to center the buffer. Choosing YES
centers the buffer.
Press [ENTER] twice to center the buffer.
Programs the RX clock phase to Normal or Inverted.
Upon entry, the status of the RX Clock is displayed. Press [↑] or [↓] to
make the selection. Press [ENTER] to execute the change.
Operation
3–19
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