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

12-1
Chapter 12. SMPTE-310
DATA INTERFACE
12.1 G
ENERAL
This plug-in module provides the physical and electrical interface between external
terrestrial data equipment and the modulator. The SMPTE-310 data interface is based on
the DVB’s Synchronous Serial Interface (SSI) used with the SDM-2020 Modulator
developed for video and high-speed data applications. 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.
12.1.1 A
PPLICABLE
D
OCUMENTS
• Comtech EF Data SDM-2020 Modulator Specification, SP/5611
• SMPTE 310M Synchronous Serial Interface for MPEG-2 Digital
Transport Stream
• TM 1449, Interfaces for CATV/SMATV Headends and Similar
Professional Equipment
12.1.2 D
ESCRIPTION
The SMPTE-310 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 12-1 shows the SMPTE 310 data interface block diagram. At a functional level,
the data interface has four I/O ports. Transmitted data by the modulator enters the
SMPTE-310 data interface at the TX input as a synchronous serial bit stream, while data
received by a demodulator is sent by the data interface at the RX outputs as a
synchronous serial bit stream. The TX and RX serial data is biphase-mark encoded. The
modem interface is byte-oriented interface with clock, data, and synchronous signals.
Finally, the auxiliary function port provides status outputs for modulator and demodulator
faults as well as input for control and transmission.