Comtech EF Data SDM-2020, Installation And Operation Manual

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SDM-2020 Satellite Demodulator Data Interfaces
Rev.3 A–51
A.6.5.5 Buffer Centering
The unit provides buffer centering capability. The buffer can be set to 50% by the
operator
via the front panel. 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%.
A.6.5.6 General Receive Specifications
Refer to Table A-32 for general RX specifications.
Table A-32. General RX Specification
RX 2047 Pattern
Generation The unit supplies a 2047 test pattern substitution into the RX data path and
perform 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.