Comtech EF Data SDM-2020, Installation And Operation Manual

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Data Interfaces SDM-2020 Satellite Demodulator
A–6 Rev.3
The following cables, or equivalent computer grade cables incorporating twisted,
shielded pairs, are recommended:
•
Belden type LV Computer M9768 (50
Ω
) 15 pairs
•
Belden 8175 (100
Ω)
15 pairs
The Belden 8175 has lower capacitance; however, it has a larger diameter and requires
the selection of an appropriate connector shell.
The typical cable length for the serial/parallel interfaces is
≤
5 meters (16.405 feet).
The interface operates to the specifications described in Table A-3.
Table A-3. RS-422 Interface Specifications
General Specifications
Interface Type RS-422/EIA-530 Synchronous, Serial/Parallel.
Data Rate 1.5 to 18 Mbit/s, serial.
1.5 to 100 Mbit/s, parallel.
Data Framing
Formats 188, 204 byte packets per ETS 300 421, and None.
Connectors 25-pin, female D for serial data, EIA-530 PIN Out
25-pin, female D for parallel or serial data, DVB PIN Out
9-pin, female D for reference clock from unit (Demodulator only), plus fault.
Electrical
Properties Per RS-422.
Parallel Signal
Types TX: TX Clock, TX Data, Data Valid, and Sync per TM1449.
The Demodulator does not require Sync or Data Valid with the 188 or 204 byte patterns.
Parallel: RX Clock, RX Data, Data Valid, and Sync per TM1449
Reference (ST equivalent).
Serial Signal
Types Serial: SD, ST, TT, RS, CS, RD, RT, RR (CD).
Voltage Level
4 ± 2V Differential into 100
Ω.
A.2.3 Configuration
Note: The jumper location on the interface card is shown in Figure A-3.
A single jumper provides the option for a transmit or receive reference clock on
connector J3 (pins 2 and 15). The pins are configured at the factory as signal ground per
TM 1449.