Comtech EF Data SDM-2020 - Manual (Page 131)

SDM-2020 Satellite Demodulator Revision 4
RS-422 Data Interface MN/SDM2020D.IOM
7–5
7.3.1 User Interfaces
The following paragraphs describe the RS-422 user interfaces.
7.3.1.1 Parallel, J3, DB25 Female (DVB Parallel/Serial Data Interface)
This data port supports DVB and DBS parallel and serial packetized data. There are three
standard frame formats supported, as follows:
• None (187)
• 188
• 204
When None (187) mode is selected,
no frame structure is expected, while the 188 and 204
modes will synchronize to standard MPEG-2 transport frames. Other supported data
formats are referenced in the appropriate section of this manual, but the data from other
frame formats is extracted and converted to one of the three modes of operation.
7.3.1.1.1 Connector Pinout, J3, Parallel/Serial DVB
The connector is a sub-miniature, 25-pin, female D connector, with threaded jack nuts
(refer to Table 7-2 for pinout). All signals on this connector are outputs from the
demodulator.
When used as a serial data port, Data 7 (pins 3 and 16) is the active data pin.
Signal assignments for pins 2 and 15
are jumper-selectable (Modulator Only). They are
defined as signal ground in the DVB definition of TM1449, but may be configured to
provide SCT out.
Refer to Section 4.3 for jumper details. Signal levels are as defined in
RS-422. Per TM1449, the differential sense of all signal pairs is a logic “1” when “A” is
positive with respect to “B.” This is the normal selection in the Function Select:
Configuration: Interface menu.