Paradyne DMD15L Rx Baseband Processing, Clock Selection, Monitor & Control M&C Subsystem

DMD15/DMD15L IBS/IDR Satellite Modem Operation

3.8.3 Rx Baseband Processing

The Receive Processor performs the inverse function of the Tx Processor. Data received from the satellite passes through the BB Loopback Circuit to the Reed-Solomon Decoder to the Deframer. The Deframer acquires the IBS/IDR frame, synchronizes the Reed-Solomon Decoder and extracts the received data and overhead from the frame structure, placing the data into the PD Buffer, sending the overhead data to the UIM. In Closed-Net Mode, the data is extracted from the buffer and is sent to the UIM. Backward Alarm indications are sent to the M&C Subsystem. In Drop and Insert Mode, the Insert Processor synchronizes to the incoming terrestrial T1/E1 Data Stream, extracts satellite channels from the PD Buffer, and then inserts them into the desired terrestrial time slots in the T1/E1 Data Stream.

3.8.4 Clock Selection

Both the Tx Clock and the Buffer Clock source may be independently locked to one of the following:

SCT (Internal Oscillator)

SCTE (External Tx Terrestrial Clock)

EXC clock (External Clock Source)

Rx Satellite Clock (Loop Timing)

Additionally, for loop timing applications the SCT Clock Source can be selected to be Rx Satellite Clock.

3.9 Monitor & Control (M&C) Subsystem

Also contained on the BB Card is the M&C Subsystem. The M&C contains a high-performance Motorola 68302 Microprocessor and is responsible for overall command and control of modem functions. The M&C is constantly monitoring all subsystems of the modem by performing a periodic poll routine and configures the modem by responding to commands input to the system. During each poll cycle, the status of each of the subsystems is collected and reported to each of the external ports and Front Panel. Performance statistics such as Eb/No, buffer fill %, etc. are compiled. If faults are detected, the M&C will take appropriate actions to minimize the effect of such faults on the system (Refer to the Fault Matrices in the Section 6 (Maintenance) of this manual).

The M&C subsystem contains the following features:

3.9.1 Asynchronous Serial Port #1

This port is dedicated to the Terminal Program. With this program, all features of the modem may be controlled and monitored by any common terminal connected to the Terminal Port.

3.9.2 Serial Port #2

This port is dedicated to the Modem Remote Port. This port may be configured to support a number of synchronous or asynchronous protocols such as HDLC, and RS-485. 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.

3.9.3 Serial Port #3

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.

TM051 - Rev. 5.8 3-9