Radyne DMD2050, Operation Manual

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DMD2050 Universal Satellite Modem Theory of Operation
TM110 – Rev. 1.3 3-7
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.
Form-C Contacts:
The UIM provides three Form-C Relays under processor control that appear at J11.
Mod Fault: De-energized when any transmit side fault is detected.
Demod Fault: De-energized when any receive side fault is detected.
Common Fault: De-energized when any fault that is not explicitly a Tx or
Rx Fault such as an M&C or Power Supply Fault.
Open Collector Faults:
The UIM provides two Open Collector Faults that appear at Pins 28 & 10 on J8.
Mod Fault: Will sink up to 20 ma (maximum) until a transmit or
common fault is detected. Will not sink current if a fault
is detected.
Demod Fault: Will sink up to 20 ma (maximum) until a receive or
common fault is detected. Will not sink current if a fault
is detected.
The open collector faults are intended for use in redundancy switch applications in order to
provide quick status indications.
3.5 Baseband Processor Card
The Baseband Processor Card (BB Card) contains two major subsystems – the Baseband
Processing System and the Monitor and Control Subsystem.