User's Manual

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.
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.
The Join/Leave word (label 271) is transmitted on the CMU bus at a minimum rate of
on
ce 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
• 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)