Remote/Terminal Port; Async Port; Ethernet Port; Clock - Radyne DMD20 Installation And Operation Manual

Theory of Operation DMD20/DMD20 LBST Universal Satellite Modem

3.1.5.1 Remote/Terminal Port

This port functions as the Modem Remote Port or Terminal Port. This port supports an
asynchronous control protocol as described in Section 4. It may be configured to support either
RS-232 or RS-485 signal levels. This port is intended for use in computer-based remote M&C.
All functions of the modem may be monitored and controlled from this port via a common terminal
connected to the Terminal Port. This function is front panel selectable.

3.1.5.2 Async Port

This port is dedicated for ES-ES Communications. The port may be configured for a number of
communications protocols. Overhead data to/from the UIM is routed to/from the framer/deframer.
This port may be configured to support either RS-232 or RS-485 signal levels. This port is also
used by SCC Framing for the in-band data.

3.1.5.3 Ethernet Port

This port is dedicated for Ethernet Communications. The port is configured for 10 Base-T
communications protocols.

3.1.5.4 Clock

The time and date is kept in order to 'time-tag' system events.

3.2 Earth Station to Earth Station Communications Port

The modem contains a selectable RS-232, or RS-485 Asynchronous Communications Port for
Earth Station-to-Earth Station Communications. The baud rate and protocol can be selected from
the Front Panel.

3.3 Terrestrial Loopback

The modem provides for terrestrial loopback. For Tx Terr Loopback the Tx Data port is looped
back to the Rx Data port after the interface driver/receiver. For RX Terr Loopback, the Receive
Data from the satellite is looped back for retransmission to the satellite, providing a far end
loopback. Tx/Rx Loopback provides both loopbacks simultaneously. Refer to Figures 3-6
through 3-8 for loopback functional block diagrams.

3.4 Modem Status

The modems M&C system is connected to most of the circuitry on any board contained in the
chassis. These connections provide status on the working condition of the circuitry as well as
providing the data required for the various measurements the modem provides. The M&C
processes this information and generates status indications as well as alarms when necessary.
Detailed status information is available via the modems various user interfaces (front panel,
remote and terminal). A summary of this information can be connected to external equipment,
switches or alarms via the open collector and/or form-C fault connections.
3-6 TM103 - Rev. 2.5