Functional Description; 8.3.1 Input/Output Data Formats; Mpeg-2 Null Packet - Comtech EF Data CDM-710 Installation And Operation Manual

CDM-710 Broadcast Satellite Modem
CDI-40 ASI Interface Module
8.3

Functional Description

Operation for either ASI is selected by programming the module for operation, either from the
CDM-710 front panel keypad/display or from the remote communications ports. Refer to Chapter
5. FRONT PANEL OPERATION or Appendix C. REMOTE CONTROL for further
information.

8.3.1 Input/Output Data Formats

The CDI-40
operates at a 270 Mbps transport rate for all data rates. The required encoding of this
transport is defined in EN 80053-9 and the Cypress Hotlink IC data sheets. See applicable
specifications section.
The information that follows applies to baseband data and not the data transformed to the 270
Mbps physical transport layer.
There are two general modes of operation (note that the Tx interface correlates from sync word or
sync signal):
ASI Sync Mode
188 Mode
204 Mode
For ASI operation, data is either constant packet arrival or constant burst arrival at the equivalent
serial data rate. The standard frame formats / MPEG-2 I/O data formats are as follows:
Data Format
Data
Transport Rate
(ASI)
8.3.1.1

MPEG-2 Null Packet

When the data input to the CDI-40 is disconnected or not synchronized the modulator sends
MPEG-2 null packets in accordance with ISO/IEC DIS 13818-1, Coding Of Moving Pictures And
Associated Audio.
If the interface is in Test mode with the patterns turned ON, the modulator sends pseudo random
pattern over the link in the 187 bytes following the sync byte whether Tx data into the modem is
present or not.
Description
The unit looks for a DVB/MPEG-2 frame consisting of 1 sync byte (0x47 ) and 187 bytes of
data. The frame structure is acquired by the interface to create a satellite frame of 204 bytes
by adding 16 bytes of Reed-Solomon check bytes. The demodulator removes the 16 check
bytes and the 188-byte frame is returned to the terrestrial circuit.
The unit expects a DVB/MPEG-2 frame consisting of 1 sync byte (0x47), 187 bytes of data
and 16 bytes of filler.
Description
Payload data is byte serial with MSB first.
For 188 Mode, the payload is 187 bytes in length, preceded by a sync word.
270 Mbps for all data rates.
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