Comtech EF Data SDM-2020 - Manual (Page 177)

SDM-2020 Satellite Demodulator Revision 4
G.703 Data Interface MN/SDM2020D.IOM
11–11
11.1.5.5 Buffer Centering
The unit provides buffer centering capability. The operator via the front panel can set the
buffer to 50%. Buffer centering also occurs automatically after each of the following:
receive signal acquisition, change in buffer size, change in buffer reference, and an
overflow/underflow condition. During overflow or underflow conditions a Demod alarm
is indicated. A buffer full condition is reported when the buffer exceeds 90% full, or
when the buffer falls below 10%.
11.1.5.6 General Receive Specifications
Refer to Table 11-10 for general RX specifications.
Table 11-10. General RX Specification
RX 2047 Pattern
Generation The unit supplies a 2047 test pattern substitution into the RX data path
and performs BER calculations on that pattern, with the results reported
to the host unit.
AIS/Data Fault Detection The unit provides AIS (all 1’s) or data fault (all 1’s or 0’s) detection on the
incoming RX data stream.
RX AIS Assertion The unit provides AIS substitution into the RX data path when
commanded by the host unit.
RX Output Stable The unit provides data stable (all 1s) into the RX data path when
installed in a unit RX data stable shall be removed when either interface
loopback or interface loop-through is turned on.
Buffer Reference Clock
Activity The unit provides activity detection for RX Satellite Clock, TX Terrestrial,
and External Clock sources. An alarm condition is communicated to the
host unit when lack of activity is detected.
RX Buffer PLL Fault
Detection The unit provides RX Buffer PLL fault detection. When the RX buffer PLL
is not locked a fault condition is communicated to the host unit.
FPGA Program Error
Detection/Reporting The unit detects TX and RX FPGA programming errors and reports
errors to the host unit.