Hssi Interface And Connectors; Figure 3-2. Hssi Interface Block Diagram - Comtech EF Data CDM-Qx Installation And Operation Manual

CDM-Qx/QxL Multi-Channel Satellite Modem with DoubleTalk™ Carrier-in-Carrier®
Rear Panel Connectors
3.3.6

HSSI Interface and Connectors

This data interface is a plug-in module that inserts into the rear of the CDM-Qx/QxL's Modulators
or Demodulators. 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.
The HSSI Card Data Interface Module plugs into the rear of the Modulator or Demodulator.
Figure 3-2 shows a block diagram of the interface.
The HSSI interface provides:
•
A single HSSI interface;
•
A DCE Connection:
o ST clock is sourced to the terrestrial interface for use as reference by DTE
o TT is treated as an incoming External Clock, and the interface phase locks to it
TA / CA is supported
o
Additionally, the module is automatically configured for simplex-transmit or simplex-receive
operation when the module is plugged into a Modulator and Demodulator. When the
CDM-Qx/QxL is configured as a modem, only the Demodulator is required to have a HSSI
Interface and the Modulator is assigned a blank panel with the Alarms output only, as shown in
Figure 3-3 on the next page.
J1
TT
SD
ST
TA
CA
RT
RD
Common
A summary of specifications for the interface is provided in Sect. 3.3.6.1; the HSSI connector pin
assignments are provided in Sect. 3.3.6.2 (see Sect. 3.3.1 for more information on the Alarms
connector).
Tx Clock Input (External)
Tx Data
Output Clock (Rate Programmable)
(RTS)
(CTS)
Rx Clock
Rx Data

Figure 3-2. HSSI Interface Block Diagram

3–10
MN/CDMQX.IOM
Processor
Processor
Mux /
Mux / Clk
Demux
&
Demux
Data
PLL
PLL
Modem
Interface
Rx
Rx
μC
Buffer
Buffer
Interface
Interface
Loopback
Loopback
Control
Control
HSSI Interface
Revision 7