Comtech EF Data CDM-700 - Manual (Page 237)

Appendix D. HSSI INTERFACE
(CDI-60)
D.1 Introduction
The CDI-60 HSSI data interface is a plug-in module that inserts into the rear of the CDM-700
series 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. 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 – located to the right center of the rear panel –
is filled with a data interface module first; Slot 2 – located to the right side edge of the chassis – is
assigned a blank panel or another interface depending upon configurations allowed at time of
order (i.e., when a HSSI module is installed in Slot 1, Slot 2 is a blank panel).
Initially, the modem is available in Duplex and Rx only configurations.
The CDI-60 plugs into the rear of the modem. Figure D-1 depicts the block diagram for the
interface. The CDI-60 HSSI interface provides:
♦ A single HSSI interface
♦ DCE
Connection
¾ ST clock is sourced to the terrestrial interface for use as reference by DTE
¾ TT is treated as an incoming External Clock, and the interface phase locks to it
¾ TA / CA is supported
Figure D-2 shows the CDI-60 HSSI interface, looking towards the real panel – the SCSI-2
connector serves as the data port. A summary of specifications for the interface is provided in
Table D-1; the connector pinout is shown in Table D-2.
D–1