Loopback – Comtech EF Data SDM-2020 User Manual
Page 162
SDM-2020 Satellite Modulator
Revision 7
ASI/LVDS Data Interfaces MN/SDM2020M.IOM
13-6
13.1.3.2
A
PPLICABLE
J
UMPER
D
ATA
When the ASI portion of the interface is used JP1 is normally positioned Off so that the
pins are not connected. Also, JP2 is normally set to On. This allows installation of the
interface in either the modulator or demodulator without moving any jumpers. Refer to
Table 13-2 for Modulator/Demodulator Jumper Selection.
Table 13-2. Modulator /Demodulator Jumper Selection
Modulator Jumper Selection
Jumper ON/OFF
Description
JP1
ON
Selects J6, the LVDS-DVB connector as an input.
JP1
OFF
Normal Setting. Selects J6 as an output for Loopback or Loop Thru operation in
conjunction with the ASI signals.
JP2
ON
Normal Setting. Selects pins 2 and 15 of J6 as GND.
JP3 Not
Used
For future use.
JP4
ON
Selects pins 2 and 15 as REFCLKB and REFCLKA outputs from J6. This is used as
a byte clock reference by other equipment.
JP4 OFF
Normal
Setting.
Demodulator Jumper Selection
Jumper ON/OFF
Description
JP1
ON
Selects J6 as an input for loopback operation.
JP1
OFF
Normal Setting. Selects J6, LVDS-DVB connector, as an output for RX data. Also, it
is used for loopback operation in conjunction with the ASI signals.
JP2
ON
Normal Setting. Selects pins 2 and 15 of J6 as GND.
JP3 Not
Used
For future use.
JP4 Not
Used
Jumper belongs on J2.
13.1.4
L
OOPBACK
In Loopback the TX input from the terrestrial circuit is routed through the interface to the
terrestrial RX output. In a modulator chassis, TX data continues to enter the modulator
and the TX IF is transmitted during Loopback.
In the demodulator, satellite data is interrupted during Loopback and the data entering the
TX connector is returned to the RX connector. Demodulator data from the satellite is not
routed to the modulator by the data interface. This is a test mode and illuminates the
TEST LED.