Comtech EF Data DD240XR Rev Е - Manual (Page 55)

DD240XR High-Speed Digital Demodulator User Interfaces
MN-DD240XR – Rev. E 4-35
4.3.8 Remote Port Packet Structure
The RLLP Remote Port Packet structure is as follows:
<SYNC>:
Message format header character that defines the
beginning of a message. The <SYNC> character value
is always 0x16. (1 byte).
<BYTE COUNT>:
Number of bytes in the <DATA> field. (2 bytes).
<SOURCE ID>:
Identifies the address of the equipment from where the
message originated. (1 byte).
<DEST. ID>:
Identifies the address of the equipment where the
message is to be sent. (1 byte).
<FSN>:
Frame sequence number ensures correct packet
acknowledgment and data transfers. (1 byte).
<OPCODE>:
This field identifies the message type associated with the
information data. The equipment processes the data
according to the value in this field. Return error codes
and acknowledgment are also included in this field. (2
bytes).
<...DATA...>:
Information data. The number of data bytes in this field is
indicated by the <BYTE COUNT> value.
<CHECKSUM>:
The modulo 256 sum of all preceding message bytes
excluding the <SYNC> character. (1 byte).
4.3.9 DD240XR Opcode Command Set
The data rate and symbol rate values must be range checked when altering: Data Rate, Symbol
Rate, Inner FEC, Modulation Type, or Framing. Use the following formulas for range checking:
Max Symbol Rate >= Symbol Rate = (Data Rate * Overhead) / (Code Rate * Modulation)
Max Data Rate >= Data Rate = (Symbol Rate * Code Rate * Modulation) / Overhead
Overhead 204/188 when framing is set to 188 bytes.
204/204 when framing is set to 204 bytes.
204/187 when framing is set to none.
Modulation 16QAM = 4
8PSK = 3
QPSK = 2
Code Rate 1/2, 2/3, 5/6, 3/4, 7/8, 8/9
Also, if an interface is being used which does not have buffering capability the buffer size may
only be set to 0 milliseconds.
Other restrictions, rules or formatting are described in the front panel or SNMP MIB portions of the
equipment manual.
The DD240 Opcode Command Set is listed below.