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SLM-7650 Satellite Modem
Operation
Menu Item
EXT MASTER CLOCK
FREQUENCY
BUFFER CLOCK
BUFFER SIZE
BUFFER CENTER
RX CLOCK PHASE
Programs the external master clock input frequency between 9.6 kHz and 20 MHz.
The data rate of the external master clock input will need to be entered by the user to
match the expected rate at the input to the modem at the data I/O connector.
Notes:
1.
If the EXT MC is selected as the timing source for the SCT PLL the
frequency of the MC must meet one of the three following:
a.
The MC frequency is equal to the transmit data rate.
b.
The transmit data rate and the MC freq. are both integer multiples of
600 Hz.
c.
The transmit data rate and the MC freq. are both integer multiples of
1 kHz.
2.
If the EXT MC is selected as the timing source for the Buffer Clock the
frequency of the MC must meet one of the three following:
a.
The MC frequency is equal to the receive data rate.
b.
The receive data rate and the MC freq. are both integer multiples of
600 Hz.
c.
The receive data rate and the MC freq. are both integer multiples of
1 kHz.
On 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.
Programs the interface buffer output clock to one of the following modes:
RX (Satellite): Turns off the buffer. This will clock the data in and out of the buffer
with the same receive satellite clock. This is the fall back when either TX
Terrestrial or the External Master Clock is missing.
SCT (Internal): Clocks the data to the user with the internal clock of the modem.
This is also the fallback clock.
External Master Clock: Clocks the data to the user with the external master clock
input. (The MC input is on the baseband data interface. The frequency
must be programmed in the Ext Master Clock Frequency menu screen.)
TX Terrestrial: Clocks the data to the user with the customers Tx Terrestrial clock
input.
Insert:
Drop and Insert applications only. Overhead must be installed.
On entry, the current setting of the plesiochronous buffer clock is displayed. Press an
arrow key to make the selection. Press [ENTER] to execute the change.
Sets the size of the buffer.
On 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 Interface Utility
menu to change the buffer units to seconds or bits. If selecting seconds, choose from
1 to 48 ms, in increments of 1 ms or 0 (Bypass). If selecting bits, choose from 32 to
1,048,576 bits, in increments of 16 bits. Press [ENTER] to execute the change. Setting
the RX buffer to RX Satellite will turn off the buffer.
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.
Press [ENTER] twice to center the buffer.
Programs the RX clock phase to Normal or Inverted.
On entry, the current status of the RX Clock is displayed. Press an arrow key to make
the selection. Press [ENTER] to execute the change.
3-13
Specifications/usage
Revision 4
MN/SLM7650.IOM
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