Front Panel Interface; Clock; Watchdog Timer; Program Flash Rom - Radyne DMD15 Installation And Operation Manual

Operation DMD15/DMD15L IBS/IDR Satellite Modem

3.9.4 Front Panel Interface

The M&C operates the Front Panel, which includes a 2 x 12 backlit LCD, Indicator LEDs, and a
Numeric Keypad.

3.9.5 Clock

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

3.9.6 Watchdog Timer

The Watchdog Timer monitors the health of the M&C Subsystem.

3.9.7 Program Flash ROM

The 512K of reprogrammable program ROM (expandable to 1 MB) is available to the M&C.

3.9.8 RAM

128K RAM (expandable to 512K)

3.9.9 Non-Volatile RAM

8K of Non-Volatile RAM (expandable to 32K) is provided in order to hold the modems current
configuration. In the case of power interruption, the M&C will reconfigure the modem identically to
the state before power was lost.

3.10 Universal Modem

The Universal Modem (UM) Card contains a complete variable rate modulator/demodulator
intended for satellite communications. The UM utilizes the latest digital technology for high
reliability and versatility. The modulator and demodulator sections may be configured
independently under processor control. The UM includes a duaL-Band 70/140 MHz IF, QAM
Modulator/Phase Lock Receiver, Convolutional Encoder/Viterbi Decoder, sequential decoding
option, Differential Encoder/Decoder, and a V.35 Scrambler/Descrambler.

3.10.1 Modulator

Processed baseband data ready for transmission enters the modulator and undergoes, if the
functions have been enabled, V.35 Scrambling and Differential Encoding. The data then
undergoes convolutional encoding and is fed to the Dual Variable Interpolating FIR Filter. The FIR
Filter shapes the data waveform to a predefined spectral mask and vectorizes the data for
mapping into a PSK Constellation. The data is then converted to an analog waveform and is
vector modulated onto an RF Carrier produced from the Transmit IF Synthesizer Circuitry. The
final output is then fed to the IF Loopback Circuitry where under microprocessor control the
Transmit Signal may be routed to the demodulator. Due to its nearly complete digital
implementation, the modulator is capable of performing virtually any modulation format, and can
produce almost any desired spectral mask. The modulator also houses the SCT and Reference
Oscillators. The Reference Oscillator provides the frequency standard for both the modulator and
demodulator. An external reference may also be selected. In this case, the Reference Oscillator
is locked to the external reference.
3-10 TM051 – Rev. 5.8