G3000 DATA Buses
Uploaded by
Hugo GarzaG3000 DATA Buses
Uploaded by
Hugo Garza_________________________________________________________________
2.2 SYSTEM COMMUNICATION
The G3000 use six main communication protocols to pass data between LRUs: ARINC 429, 717,CAN
Ethernet/HSDB, RS‐232, and RS‐485. This section describes each one with the rationale behind its
selection.
ARINC 429
The G3000 system utilizes uni‐directional high (100k bits/second) and low speed (12.5k
bits/second)ARINC 429 communication with parity integrity check. G3000 ARINC 429 data complies
with the ARINC specification. This communication protocol was chosen for AHRS and air data because
ARINC 429 is the standard aviation communication protocol for AHRS data. ARINC 429 communication
in the G3000 system is utilized as follows:
Path for AHRS data into the GDUs (primary path for displayed data).
Path for AHRS data into the GIAs (backup path for displayed data in the event that the primary
data path fails and primary path for AHRS data that is sent to the servos for AFCS purposes).
Path for ADC data into the GDUs (primary path for displayed data) and the on‐side GRS units.
Path for ADC data into the GIAs (backup path for displayed data in the event that the primary
data path fails and primary path for ADC data that is sent to the servos for AFCS purposes).
Ethernet/HSDB
The G3000 utilizes a proprietary communication protocol called HSDB (High‐Speed Data Bus) to provide
upper level communication capabilities, with point‐to‐point, full duplex channels capable of 10 Mbits/s
data rates. This protocol was designed to give the required integrity and functionality with minimal
additional overhead found in other more standard higher level Ethernet communication protocols and
provides guaranteed delivery of asynchronous packets through an acknowledge protocol. Additionally,
the HSDB communication protocol monitors the age of the communication data and contains routing
information that the receiving sub‐system utilizes to determine if the data needs to be passed along to
another sub‐system. The communication packets use an IEEE Standard 802.3 data link layer that utilizes
broadcast messages. In the G3000 system this protocol is utilized as follows:
Exclusive communication path between GDUs, GIAs, GSDs, GWX, GTS, and GDL.
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RS‐232
The G3000 system utilizes uni‐directional or bi‐directional configurable baud rate, tipically 9600 bits/second
(aprox 10k bits/second), RS‐232 communication in the G3000 system is utilized as follows:
Path between the GIAs and on‐side GRS and GDC units for system installation configuration
data and code uploading capabilities. This data path is also used by the GIA to send GPS data to
the GRS. This communication protocol uses a CRC‐16 integrity check. This communication
protocol was chosen because of the requirement for two way communication. This data is
checked by a CRC‐32 before being used by the GRS and GDC.
Primary path between the GIA and the GTX for pilot selection of the unit operating mode,
transponder identification code, position identification mode and status information from the
transponder such as the operating mode, transponder identification code, position
identification mode and reply annunciation. This communication protocol uses a checksum
scheme to validate the data. This communication protocol was chosen because of the two way
communication requirement with the GTX in a low noise environment with low criticality data
and because it is the communication protocol used in previously‐certified Garmin transponder
products.
Path from GRS 77 to the GMU 44 utilized for code uploading. This communication protocol uses
a CRC‐16 integrity check. This communication protocol was chosen because of the requirement
for a minimum number of pins on the connector of the GMU 44. The data being sent to the
GMU 44 is code upload data which is checked by a CRC‐32 before being used.
Primary path between the GIA and the GMA for VHF COM selection information and code and
configuration uploading. This communication protocol uses a cyclid redund code CRC‐16 integrity check.
This communication protocol was chosen because of the requirement for two way communication
with these sub‐systems of low criticality data.
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RS‐485 / RS-422
The G3000 system utilizes RS‐485 bi‐directional & RS-422 uni-directional communication channels with
baud rate of 115.2k bits/second and CRC‐16 integrity check. RS‐485 communication in the G3000
Cyclic Redundancy Chech
system is utilized as follows:
Communication between the GIAs and the GEAs to communicate engine and airframe data. The
communication with the GEA is a dedicated point‐to‐point communication used for data being
passed in both directions. This communication protocol uses a token passing protocol to handle
bus arbitration.
Communication between the GIAs and the GSAs.
AHRS Modes Available AHRS Functions Available Sensor Inputs
Pitch Roll Heading GPS Input (at GMU 44 GDC 74B Air
least one) Magnetometer Data
Computer
Normal X X X X X X
Reversionary: No X X X ----- X X
GPS
Reversionary: X X ----- X ----- X
No
Magnetometer
Reversionary: X X ----- X ------ -----
No
Magnetometer
No Air Data
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