. Decodes the satellite data.
. Computes aircraft position; this is referred to hereafter as the
navigation solution.
. Outputs the aircraft position
429 output bus.
c Outputs the aircraft position
429 output bus.
The GPSSU interfaces with the fo-
and satellite informationon the ARINC
and satellite
lowing devices
● Global positioning inertial reference units
● Inertial navigation units (INUS).
● Digital air data computers (DADCS).
● Flight management systems (FMSS).
nformation on the ARINC
GPIRUS).
3. Avionics Standard Communications Bus (ASCB) Descri~tion
The ASCB is a communication bus system that allows transmission of data in
all directions between subsystems in an aircraft. An example bus system,
shown in Figure 3, consists of two pairs of interconnecting wires which form
redundant communication paths between subsystems.
These two paths are called
Bus A and Bus B. Three bus controllers are used to manage all data transfer
activity. With dual interconnections and triplex bus controllers, bus
availability from the essential to highly essential level is achieved. The
bus controllers reside in each SG-884 Symbol Generator. Only one bus
controller is active at any time. The others act as backup controllers and
assume control of the bus when required due to failure of the active
controller.
Data transfer between users on the bus is controlled by the active bus
controller. Each user is requested by the active bus controller using the
request address of the user to transmit or talk his predefine data message
onto the bus in sequence. During this time, any other users on the bus may
accept the data message as desired but cannot transmit or talk.
Each user has a defined address or label (user address) and a message, with
all transmitted parameters in a defined order.
There are no labels on
individual data parameters as in ARINC 429; thereby, bus overhead is
significantly reduced.
The only labels in the bus system are the user
addresses, similar to the ARINC 429 equipment identifier.
The request
addresses of the users and the user addresses are listed in Table 2. The
Gulfstream IV uses version B ASCB also known as clockless ASCB.
22-14-00
Page 19
Apr 15/93
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