Comtech EF Data SDM-2020 - Manual (Page 148)

SDM-2020 Satellite Demodulator Revision 4
ASI/RS-422Data Interface MN/SDM2020D.IOM
9–4
Table 9-1. ASI/RS-422 Specifications
General Specifications
Data Framing Formats 188, 204 byte packets per ETS 300 421, and None.
Hot Pluggable Not required. Unit power is turned off prior to removal or insertion
of the data interface.
ASI Specifications
Data Rate
1.5 to 100 Mbps ASI.
Clock Rate Uncertainty Programmed data rate ± 100 ppm.
Transport Clock ASI The transport rate is 270 Mbps for all data rates.
Impedance 75 Ω.
Return Loss 15 dB, frequencies, 5 to 270 MHz.
Connectors BNC female, 75 Ω.
Electrical Properties Per TM 1449
Packet Types Burst or distributed.
Signal Types Serial data.
Voltage Level 800 mV ± 10% into 75 Ω.
ASI Data Loop 3 dB
Cutoff Frequency
2 Hz
(see Note 2)
Jitter Tolerance Meets ITU-T G.823 (3/93) and ITU-T G.824 (3/93)
Jitter Transfer ≤ 0.5 dB peaking up to cutoff frequency.
–20 dB per decade beyond cutoff.
Cable Length, Typical RG59
50 m
Belden 8281
70 m
RS-422 Specifications
Data Rate
1.5 to 18 Mbps, serial RS-422.
Clock Rate Uncertainty Programmed data rate ± 100 ppm.
Connectors 25-pin D female per EIA-530.
Electrical Properties Per RS-422.
Signal Types SD, TT, ST, RD, RT, RS, RR, CS, and DM.
Data synchronization is detected by correlating the data stream
for the MPEG2 sync pattern per ETS 300 421.
Voltage Level 4-± 2V differential into 100 Ω.
Notes:
1. Loopback – The yellow TEST MODE LED is illuminated when Loopback is turned
On. During Loopback input data is looped back to the terrestrial data output
connector(s) and data continues into the modulator.
2. Loop Thru – Operation is nearly identical to Loopback, except the yellow LED is not
illuminated. Conceptually, the data output is operating as a monitor point.
3. Rev. A or later assemblies include this capability. Rev. dash (-) assemblies can be
upgraded to this capability.