EMS Technologies Canada Ltd. HSD-MK2 Manuel D’Utilisation
SYSTEM DESCRIPTION, INSTALLATION, AND MAINTENANCE MANUAL
eNfusion® HSD-440 Mark 2 Terminal
23-15-30
F-5
3 JUN 10
C. Understanding Join/Leave Word; Label 271
Each of the Aeronautical Telecommunications Network (ATN) subnetworks transmits join
and leave words to the CMU whenever a path to a specified ground address changes.
and leave words to the CMU whenever a path to a specified ground address changes.
The join event notifies the CMU that a new path to a specified ground address is available,
triggering ATN air-to-ground communications. The leave event notifies the CMU that a
path to a specified ground address has been closed, ending ATN air-to-ground
communications.
triggering ATN air-to-ground communications. The leave event notifies the CMU that a
path to a specified ground address has been closed, ending ATN air-to-ground
communications.
The Join/Leave word (label 271) is transmitted on the CMU bus at a minimum rate of
once per second or be event driven based on log on and log off events as specified by
the 'CMU - SDU JOIN/LEAVE WORD TRANSMISSION' ORT parameter.
once per second or be event driven based on log on and log off events as specified by
the 'CMU - SDU JOIN/LEAVE WORD TRANSMISSION' ORT parameter.
Table F-4 shows the definitions of the bits in the join/leave word.
Table F-4 Join/Leave Word Bits
Bits
Defines
Bits 8–1
Word Label 271:
•
Uses the A429 convention
•
Coded as 10011101
Bits 16–9
GES ID:
•
0 is an invalid ID
•
FF is used for all GESs
•
ID numbers between 1 and FE are valid GES IDs
•
GES ID is known to the HSD-440 Mark 2 Terminal
•
Bits are cleared when the HSD-440 Mark 2 Terminal is not logged on
Bits 22–17
Satellite ID
Bits 25–23
Inmarsat Service:
•
Aero H+ 011
Bits 28–26
Not used; padded with zeros
Bit 29
Data link from the AES to the GES:
•
Available (a Join message; Bit = 1)
•
Not Available (a Leave message; Bit = 0)
•
Identified by the GES ID and Satellite ID fields
•
CMU uses this information to initiate network layer virtual circuits with
available ground routers by determining the ground routers’ DTE
addresses from the provided GES identity
available ground routers by determining the ground routers’ DTE
addresses from the provided GES identity
•
Bits 9–16, (GES) and Bits 17–22 (Satellite ID) uniquely identify a GES
•
Aero Service Type field may be used by the CMU to make routing decisions
•
Bit is cleared when the HSD-440 Mark 2 Terminal is not logged on.
Bits 31–30
SSM information (ARINC 429 para 2.1.5.2)