Product specifications

Chapter 12. CDI-60 HSSI Interface
12.1 Introduction
This data interface is a plug-in module that inserts into the rear of the modem chassis. It provides
physical and electrical connection between the external terrestrial device and the internal circuitry
of the modulator or demodulator. By convention, a modem is Data Communications Equipment
(DCE) where Tx data enters the data interface and Rx data exits it. The plug-in interface has full
duplex capability.
In addition, the module is automatically configured for simplex-transmit or simplex-receive
operation when the module is plugged into a simplex chassis configured for modulator only or
demodulator only operation. Slot 1 of the modem is filled with a data interface card first, and Slot
2 is assigned a blank panel or another interface depending upon configurations allowed at time of
order. (Slot 1 is located near the center of the rear panel, and Slot 2 is next to the outside edge.)
The CDI-60 is a HSSI Card data interface module that plugs into the rear of the modem. Figure
12.1 provides a block diagram of the interface.
The HSSI interface provides:
• A single HSSI interface
• Supports 188 byte MPEG-2 transport stream only
• DCE Connection:
o RT is derived from the received satellite clock and is provided to the DTE as a
receive data clock.
o ST is equivalent to the modem transmit rate and is sourced to the terrestrial interface
for use as a reference by the DTE.
o TT is treated as an incoming Transmit Clock. TT must be equal to the transmit data
rate. The precision of TT must be </= 100ppm.
Figure 12-2 shows a picture of the CDI-60 HSSI interface and the SCSI-2 connector that serves
as the data port. A summary of specifications for the interface is provided in Table 12-1 and the
connector pinout is shown in Table 12-2.
When a HSSI card is installed in Slot 1, Slot 2 is a blank panel.
12–1