Product specifications
CDM-710 Broadcast Satellite Modem Revision 10
CDI-40 ASI Data Interface MN/CDM710.IOM
10.3 Input/Output Data Formats
The ASI interface 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 description 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. There are three standard frame formats
(Table 10-2) supported.
Note: The Tx interface correlates from sync word or sync signal.
ASI Sync modes:
188 Mode:
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.
204 Mode:
The unit expects a DVB/MPEG-2 frame consisting of 1 sync byte (0x47), 187
bytes of data and 16 bytes of filler.
For ASI operation data is either constant packet arrival or constant burst arrival at the equivalent
serial data rate. See Table 10-2 for input/output formats.
Table 10-2. MPEG-2 Input/Output Data Formats
Data Format Description
DATA Payload data is byte serial with MSB first.
For 188 the format, the payload is 187 bytes in length, preceded by
a sync word.
TRANSPORT RATE (ASI) 270 Mbps for all data rates.
10.3.1 MPEG-2 Null Packet
When the data input to the ASI interface 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.
0x47
Sync
Byte
0x1F, 0xFF, 0x1F 0xFF
Bytes 2-5
Not S
p
ecified
10–5