DM240XR High-Speed Digital Modulator
User Interfaces
TM120 – Rev. 1.1
4-23
<SYN> - the message format header character, or ASCII sync character, that defines the
beginning of a message. The <SYN> character value is always 16h.
<BYTE COUNT> - the Byte Count is the number of bytes in the <DATA> field, ranging from 0
through TBD. This field is 2 bytes long for the DM240 protocol.
<SOURCE ID> - the Source Identifier defines the message originator’s multidrop address.
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.
Table 4-4. Checksum Calculation Example
BYTE FIELD
DATA CONTENT
RUNNING CHECKSUM
<BYTE COUNT> (Byte 1)
00h = 00000000b
00000000b
<BYTE COUNT> (Byte 2)
02h = 00000010b
00000010b
<SOURCEID>
F0h = 11110000b
11110010b
<DESTINATION ID>
2Ah = 00101010b
00011100b
<FSN> 09h
=
00001001b
00100101b
<OPCODE> (Byte 1)
00h = 00000000b
00101000b
<OPCODE> (Byte 2)
03h = 00000011b
00101000b
<DATA> (Byte 1)
DFh = 11011111b
00000111b
<DATA> (Byte 2)
FEh = 11111110b
00000101b
Содержание DM240XR
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Страница 10: ...Table of Contents DM240XR High Speed Digital Modulator x TM120 Rev 1 1 ...
Страница 12: ...Introduction DM240XR High Speed Digital Modulator 1 2 TM120 Rev 1 1 ...
Страница 16: ...Installation DM240XR High Speed Digital Modulator 2 4 TM120 Rev 1 1 ...
Страница 19: ...DM240XR High Speed Digital Modulator Theory of Operation TM120 Rev 1 1 3 3 ...
Страница 55: ...User Interfaces DM240XR High Speed Digital Modulator 4 36 TM120 Rev 1 1 ...
Страница 67: ...Rear Panel Interfaces DM240XR DVB High Speed Digital Modulator 5 12 TM120 Rev 1 1 ...
Страница 69: ...Maintenance and Troubleshooting DM240XR High Speed Digital Modulator 6 2 TM120 Rev 1 1 ...
Страница 79: ...Technical Specifications DM240XR High Speed Digital Modulator 7 10 TM120 Rev 1 1 ...
Страница 103: ...Appendix A DM240XR High Speed Digital Modulator A 24 TM120 Rev 1 1 ...
Страница 124: ...DM240XR High Speed Digital Modulator Appendix B TM120 Rev 1 1 B 21 ...