Radyne DMD15 Installation And Operation Manual page 96

DMD15/DMD15L IBS/IDR Satellite Modem
<SOURCE ID>:
<DESTINATION ID>:
<FRAME SEQUENCE NUMBER>:
<OPCODE>:
<DATA >:
<CHECKSUM>:
BYTE FIELD
<BYTE COUNT> (Byte 1)
<BYTE COUNT> (Byte 2)
<SOURCEID>
<DESTINATION ID>
<FSN>
<OPCODE> (Byte 1)
<OPCODE> (Byte 2)
<DATA> (Byte 1)
<DATA> (Byte 2)
TM051 - Rev. 5.8
The Source Identifier defines the multi-drop address
origin.
Note: All nodes on a given control bus have a unique
address that must be defined.
The Destination Identifier serves as a pointer to the
multi-drop destination device that indicates where the
message is to be sent.
The Frame Sequence Number (FSN) is a tag with a
value from O through 255 that is sent with each
message. It assures sequential information framing and
correct equipment acknowledgment and data transfers.
The Operation Code field contains a number that
identifies the message type associated with the data that
follows it. Equipment under MCS control recognizes this
byte via firmware identification and subsequently steers
the DATA accordingly to perform a specific function or
series of functions. Acknowledgment and error codes are
returned in this field. 1 Byte for the DMD5000 protocol,
and 2 Bytes for the DMD15 protocol.
The Data field contains the binary, bi-directional data
bytes associated with the <OPCODE>. The number of
data bytes in this field is indicated by the <BYTE
COUNT> value.
The checksum is the modulo 256 sum of all preceding
message bytes, excluding the <SYNC> character. The
checksum determines the presence or absence of errors
within the message. In a message block with the
following parameters, the checksum is computed as
shown in Table 4-7.
Table 4-7. Checksum Calculation Example
DATA CONTENT
00h = 00000000b
02h = 00000010b
F0h = 11110000b
2Ah = 00101010b
09h = 00001001b
00h = 00000000b
03h = 00000011b
DFh = 11011111b
FEh = 11111110b
User Interfaces
RUNNING CHECKSUM
00000000b
00000010b
11110010b
00011100b
00100101b
00100101b
00101000b
00000111b
00000101b
4-45