Comtech EF Data SDM-100A - Manual (Page 53)

SDM-100A Satellite Modem Operation
Rev. 0 3–19
B-Band Loop Back Programs the modem for baseband loopback operation (test mode).
When baseband loopback is turned on, the data and timing signals
are hard-wired (via relays) from the demodulator to the modulator on
the modem side of the interface. The Data Terminal Equipment (DTE)
baseband signals are also looped back from the transmitter data and
clock to the receiver data and clock on the customer side of the
interface. This is a bi-directional loopback of the baseband data.
Refer to Figure 3-28 for a block diagram of baseband loopback
operation.
On entry, the current status is displayed. Press [
↑ ] or [ ↓ ] to select ON
or OFF. Press [ENTER] to execute the change.
Buffer Size This configuration function is used to set the size of the buffer.
On entry, the current buffer length is displayed. Press [
↑ ] or [ ↓ ] to
select the desired buffer size. The buffer size will be displayed in
milliseconds or bits. (To change the buffer units to milliseconds or
bits, enter the “Function Select Utility” menu, select the “Interface
Utility” menu, and select Buffer Program.) The range which may be
selected is 64 to 65,536 bits, in increments of 16, or Bypass, which
equals 0 bits. If milliseconds are selected, 0 to 50 ms, in increments
of 1 ms may be chosen. Press [ENTER]
to execute the change.
Note: To have the modem calculate the buffer depth, set the buffer
units to milliseconds. When a specific buffer depth is desired, set the
buffer units to bits. To select bits or milliseconds, enter the “Utility
Interface” menu, and make the change.
Buffer Center Configuration function used to center the buffer.
On entry, the current status is displayed. Press [
↑ ] or [ ↓ ] to select YES
or NO. Press [ENTER] to execute the change.
Loop Timing This puts the modem in a loop timing configuration. The buffer clock and
the ST pin on the interface are forced to the RX clock. Available only
with the ASYNC option installed.
On entry, the current status is displayed. Press [
↑ ] or [ ↓ ] to select YES
or NO. Press [ENTER] to execute the change.
ASYNC Interface This turns the ASYNC overhead ON or OFF.
TX Baud This programs the TX UART to the desired baud rate for the ASYNC
channel. Available only with the ASYNC option installed.
RX Baud This programs the RX UART to the desired baud rate for the ASYNC
channel. Available only with the ASYNC option installed.
TX Length This programs the TX UART to the desired number of data bits.
Available only with the ASYNC option installed.
RX Length This programs the RX UART to the desired number of data bits.
Available only with the ASYNC option installed.
TX Parity This programs the TX UART for the desired parity. Available only with
the ASYNC option installed.
RX Parity This programs the RX UART for the desired parity. Available only with
the ASYNC option installed.
TX Stop This programs the TX UART to output the desired number of stop bits.
Available only with the ASYNC option installed.