Comtech EF Data DM240XR - Manual (Page 54)

DM240XR High-Speed Digital Modulator User Interfaces
MN-DM240XR– Revision 13 4–32
All nodes on a given control bus have a unique address that must be defined.
<DESTINATION ID> - The Destination Identifier specifies the multidrop address of the
device(s) to which the message is sent.
<FRAME SEQUENCE NUMBER> - The FSN is a tag with a value from 0 through 255 that is
sent with each message. It assures sequential information framing and correct equipment
acknowledgment and data transfers.
<OPCODE> - The Operation Code field contains a number that identifies the message type
associated with the data that follows it. Acknowledgment and error codes are returned in this
field. This field is 2 Bytes for the DM240 protocol.
<...DATA...> - The Data field contains the binary, data bytes associated with the
<OPCODE>. The number of data bytes in this field is indicated by the <BYTE COUNT> value.
<CHECKSUM> - The checksum is the modulo 256 sum of all preceding message bytes,
excluding the <SYN> 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 below in Table 4-4.
IMPORTANT