Kongsberg Seatex AIS 100 Instruction Manual page 61

Seatex AIS 100 Instruction Manual, rev. 5
NOTE 1
acknowledgement process active for the acknowledgement
that was received.
ABM – Addressed Binary and safety related
message
This sentence supports ITU-R M.1371 messages 6 and 12. It provides
an external application with a means to exchange data using an AIS.
The message data is defined by the application only – not the AIS.
This message offers great flexibility for implementing system
functions that use the AIS like a communications device. After
receiving this sentence, the AIS initiates a radio broadcast on the VHF
Data Link (VDL) of either message 6 or 12. The AIS will make up to
four broadcasts of the message. The actual number will depend on the
reception of an acknowledgement from the addressed "destination"
AIS. The default time between retries is 4 s. Retries will not be
attempted more frequently than 4 s. Retries stop when the appropriate
acknowledgement (See ITU-R M.1371 messages 7 and 13.) is
received. The AIS will make up to 4 broadcasts, original broadcast
plus three retires. This process could take 32 s to complete.
The success or failure of the reception of this broadcast by the
intended AIS unit is confirmed through the use of the "Addressed and
binary Broadcast Acknowledgement (ABK)" sentence formatter, and
the processes that support the generation of an ABK-sentence. The
AIS is also limited in the amount of encapsulated data that can be sent
in each slot and frame. If the length of the message would exceed five
slots, or the AIS broadcast would exceed the limit of 20 RATDMA
slot transmissions for the current frame, the AIS will return an ABK-
sentence with an acknowledgement of "2" – message could not be
broadcast.
The total number of sentences required to transfer the binary message
data to the AIS unit. The first field specifies the total number of
sentences used for a message, minimum value 1. The second field
53
External interfaces