Consilium SELUX ST, Инструкция по установке и обслуживанию

Страница: 39 / 180

SERIAL INTERFACE SPECIFICATION
2.4 Rev. E
VDM – AIS VHF data-link message
defined in ITU-R M.1371 and as received on the VHF Data Link (VDL), using the “six-bit”
field
type. The structure provides for the transfer of long binary messages by using multiple
sentences.
Data messages should be transmitted in as few sentences as possible. When a data
message
can be accommodated in a single sentence, then it shall not be split.
!--VDM,x,x,x,a,s—s,x*hh<CR><LF>
Number of fill-bits, 0 to 5 (see Note 5)
Encapsulated ITU-R M.1371 radio message (see Note 4)
AIS channel (see Note 3)
Sequential message identifier, 0 to 9 (see Note 2)
Sentence number, 1 to 9 (see Note 1)
Total number of sentences needed to transfer the message,
1 to 9 (see Note 1)
NOTE 1
The length of an ITU-R M.1371 message may require the transmission of
multiple sentences. The first
field specifies the total number of sentences used for a message, minimum
value 1. The second field identifies the
order of this sentence in the message, minimum value 1. These cannot be
null fields.
NOTE 2
The sequential message identifier provides a message identification number
from 0 to 9 that is
sequentially assigned and is incremented for each new multi-sentence
message. The count resets to 0 after 9 is
used. For a message requiring multiple sentences, each sentence of the
message contains the same sequential
message identification number. It is used to identify the sentences
containing portions of the same message. This
allows for the possibility that other sentences might be interleaved with the
message sentences that, taken
collectively, contain a single message. This should be a null field for
messages that fit into one sentence.