Comtech EF Data SDM-2020 - Manual (Page 129)

SDM-2020 Satellite Demodulator Revision 4
RS-422 Data Interface MN/SDM2020D.IOM
7–3
The following cables, or equivalent computer grade cables incorporating twisted,
shielded pairs, are recommended:
• Belden type LV Computer M9768 (50Ω) 15 pairs
• Belden 8175 (100Ω) 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 7-1.
Table 7-1. RS-422 Interface Specifications
General Specifications
Interface
Type RS-422/EIA-530 Synchronous, Serial/Parallel.
Data Rate 1.5 to 18 Mbps, serial.
1.5 to 100 Mbps, 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.