Comtech EF Data SDM-2020 - Manual (Page 157)

13-1
Chapter 13. ASI/LVDS
DATA INTERFACE
13.1 ASI/LVDS I
NTERFACE
This plug-in module provides the physical and electrical interface between external
terrestrial data equipment and the modulator. The ASI/LVDS implements the two most
popular DVB data interfaces. The data is input/output on a BNC female connector as an
800 mV signal with biphase mark encoding. A separate auxiliary connector provides fault
status
.
13.1.1 A
PPLICABLE
D
OCUMENTS
EN 50083-9, Interfaces for CATV/SMATV Headends and Similar Professional Equipment
13.1.2 D
ESCRIPTION
The ASI/LVDS data interface is a plug-in module that inserts into the rear panel of the
chassis. The data interface provides a physical and electrical connection between the
external terrestrial circuit and the internal circuitry of the unit. By convention, a modem
is Data Communications Equipment (DCE) where transmit data enters the data interface
and receive data exits. The data interface has full-duplex capability but is automatically
configured for simplex-transmit or simplex-receive operation, depending upon whether it
is plugged into a modulator or demodulator chassis
.
Figure 13-1 shows the ASI/LVDS data interface block diagram. At a functional level, the
data interface has three ASI I/O ports. One port is LVDS interface and an auxiliary
connector. Transmitted data into the modulator enters the ASI/LVDS data interface at the
TX input as a synchronous serial data stream, while data received by a demodulator is
sent by the data interface at the RX outputs as a synchronous serial data stream. The ASI
data stream is a serial, high-speed 8B/10 encoded signal, while the outputs for modulator
and demodulator faults as well as input for control and transmission. Figure C-21
illustrates the ASI/LVDS module assembly.