Avionics Data Buses



What makes an Avionics bus: The important factors of avionics buses include; Deterministic behavior, Fault tolerance, and Redundancy.
Most avionics buses are serial in nature.
A serial bus using only a few sets of wires keeps the point to point wiring and weight down to a minimum.
MIL-STD-1553 (rev B) is the best known military example, having been developed in the 1970s.
The trend seems to be moving to Fiber buses, MIL-STD-1773 being the fiber version of 1553.
Switched fabric networks are used to provide Fault tolerance....





Bus Standards Organizations Info: The US Military uses terms like MIL-STD-xxxx (Military Standard-"Doc #"). The United Kingdom (UK) uses DEF-STAN-xxxx (Defense Standard-"Doc#"), NATO calls their specifications STANAG (Standard Agreement). In some cases US military standards are transferred to a commercial standards agency for control. In these cases the military standard is retired and the document takes on the name of the commercial agency. In the case of the 1553B bus, the name changed from MIL-STD-1553B (US government standard) to AS 1553B (SAE standard). Aeronautical Radio inc. produces many of the commercial avionics standards, termed ARINC #. Of course the IEEE or ANSI control many bus standards.


SAE Standards

AIR1189 Airborne Internal Interface Standards for Moderate Bit Rate Digital Time Division - Multiplex Systems
AIR4013A Multiplex Data Bus Networks for Mil-Std-1760 Stores
ARP4258 Application of Low Speed Avionic System Discrete Signal Interfaces
AS15531 Digital Time Division Command/Response Multiplex Data Bus
AS4075 High Speed Ring Bus (Hsrb) Standard
AS4075/1 Optical Implementation Relating to the High Speed Ring Bus (Hsrb) Standard
AS4710 Pi-Bus
AS5370 Multi-Transmitter Bidirectional Fiber-Optic Data Bus for Distributed Aircraft Control Systems
AS5643 IEEE-1394b Interface Requirements for Military and Aerospace Vehicle Applications

DO-178B; Software Considerations in Airborne Systems and Equipment Certification, an aviation industry standard since 1992.
DO-178C standard is being worked on for release in 2011.
DO-254; Design Assurance Guidance for Airborne Electronic Hardware, put into effect on FPGA/ASIC designs via AC 20-152 in 2005
DO-297; Integrated Modular Avionics (IMA) Development Guidance and Certification Considerations
EASA; European Aviation Safety

Time Triggered Protocol

SAE AS6003 TTP Communication Protocol


ARINC 659

Backplane Data Bus for Integrated Modular Avionics Backplane Data Bus, operates at 60Mbps as a commercial aviation bus.
SAFEbus architecture, developed by Honeywell is based on ARINC 659 [used on the Boeing 777 aircraft].

MIL-STD-2204 (FDDI), or (SafeNet)


ARINC 629

Multi-Transmitter Data Bus. A time division serial data bus which operates over cable at 2Mbps. Developed by Boeing.
ARINC 629 is implemented on the Boeing 777 and some models of the Boeing 737.


ARINC 429

Digital Information Transfer System. ARINC 429 is a Point-to-point unidirectional multidrop topology, using 2-wire Bi-Polar twisted-pair wiring, and Return-to-Zero signaling.
ARINC 429 uses 78 Ohm unbalanced shielded twisted pair copper cable connecting up to 20 loads from a single source. The message length is a 32 bit data word. 100K or 12.5K bit rate.
May use Williamsburg Protocol, which transferred blocks of data. Similar to ARINC 575, but being replaced by 629.
ARINC 429 is the phyiscal layer for the Aeronautical Telecommunications Network (ATN), which is the Application layer.
The Transport and Network layer is called the Aircraft Communications Addressing Reporting System (ACARS).
ARINC 429 is used for flight controls on the Boeing 777.


ARINC 818

ARINC 818 released in Jan. 07, is a video interface and protocol standard developed for high bandwidth, low latency, uncompressed digital video transmission.
Video systems include: infrared and other wave length sensors, optical cameras, radar, flight recorders, map/chart systems, synthetic vision, image fusion systems, heads-up displays and heads-down multifunction displays, and video concentrators.
ARINC 818 is a point-to-point, 8B/10B encoded serial protocol for transmission of video, audio, and data.
The protocol is packetized, but is video-centric and very flexible, supporting a single link or the transmission of a single stream over a dual link.
For additional information refer to arinc818.com


IEEE-std-1393

Spaceborne Fiber Optic Data Bus (SFODB); 1 Gb/s, fiber.
Fiber Optic Data Bus Publications, EO-1


TM-Bus

TM-Bus {Test and Maintenance - Bus}. Works in conjunction with the PI-Bus. Adapted by both JIAWG and SAE.

IEEE Std 1149.5-1995 IEEE Standard for Module Test and Maintenance Bus (MTM-Bus) Protocol
Specifies a serial, backplane, test and maintenance bus (MTM-Bus)..... between a Test Control Master and up to 250 Slave modules. The interface has 5 signals:
MTM Clock (MCLK), MTM Control (MCTL), MTM Master Data (MMD), MTM Slave Data (MSD), and MTM Pause Request (MPR).
This specification is used at the Board level while 1149.1 is used at the chip level.


PI-Bus

SAE-AS4710; PI-Bus {Parallel Interface - Bus}. Similar to VME structure, uses BTL logic. Avionics Fault-tolerance bus (JAIWG).
Also called ~ Parallel Intermodule - Bus. Provides a 32 bit wide data bus, with a 50MBytes per second transfer rate. Uses a preemptive, priority-based protocol

Search Key Words: JIAWG: Joint Integrated Avionics Working Group, ARINC: Aeronautical Radio Inc.,
ATA: Advanced Tactical Aircraft, ATF:Advanced Tactical Fighter, National Semiconductor app note: AN-725


SpaceWire

IEEE 1355.2: SpaceWire, based on the HIC (IEEE-1355) bus, and Low Voltage Differential Signaling (EIA-644).
Also controlled by the European Space Agency, for the ECSS [European Cooperation for Space Standardization].
ECSS-E-50-12 Defines the Mechanical, Electrical, and Protocol. At data rate of 100Mbaud (min.) over a distance of 10 meters

The main SpaceWire page is now listed on the SpaceWire Avionics Bus page.

SpaceWire Serial Point-to-Point Links ECSS-E-50-12; Draft Issue C
SpaceWire Links, Nodes, Routers and Networks ECSS-E-50-12; Draft Issue 2

Connector and pinout per IEEE1355 [shown], which differs from SpaceWire.

SpaceWire physical IC




AFDX

ARINC 664
Avionics Full Duplex Switched Ethernet, AFDX Network. Also seen as Avionics Full DupleX Switched Ethernet


HSDB

SAE AS4074.1 Linear Token Passing Multiplex Data Bus. HSDB; High Speed Data Bus. A fiber optic bus operating at 80 Mbps. Serial bus.
SAE AS4075 HSRB; High-Speed Ring Bus.


ASCB

ASCB Avionics Standard Communications Bus. A high-speed, bi-directional digital data bus

CSCB

CSCB Commercial Standard Communications Bus. A high-speed, bi-directional digital data bus

CSDB Commercial Standard Digital Bus. A Low-speed, uni-directional digital data bus based on RS-422 Bus.
CSDB uses a low-speed version of 12,500 bps or a high-speed version of 50k bps.


Military Avionics Data Buses - on their own pages

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Note; Fly-By-Wire uses copper wire, Fly-By-Light uses Fiber.

MIL-STD-1553 is a DOD Military (MIL) Standard (STD), which defines both the Mechanical, Electrical, and Functional characteristics.
MIL 1553 uses a Balanced (Differential) interface. The interface is dual redundant with between 2 and 32 interface devices on the bus.
Communication over MIL-STD-1553 is half-duplex at a speed of 1Mbps using 75 ohm copper wire cable.
NATO calls MIL-STD-1553B: STANAG 3838AVS;, the UK calls it DEF STAN 00-18.
Now controlled by the SAE as AS15531, and re-released by NATO as STANAG 7155.
ARINC 629; is another derivation of MIL-1553 used by commercial aircraft. Yet another was ARINC 453.

MIL-STD-1760 is a variant of the MIL-STD-1553 bus, primarily used with weapons buses on aircraft.
It follows the normal 1553 protocol but certain messages require a Cyclical Redundancy Check (CRC) be used as the last word in the message.
It also requires a header, to be used as the first word in messages to certain sub-addresses.

MIL-STD-1397C Input/Output Interfaces, Standards Digital data, Navy Systems (NTDS: Naval Tactical Data System)

MIL-STD-1773 or Buses / MIL-STD-1773

NATO calls MIL-STD-1773: STANAG 3996AVS; Now controlled by the SAE as AS1773
STANAG 3910; A derivation of MIL-1553 (like MIL-1773 ?) used in NATO / UK. Operates at 100Mb/s over fiber.

MIL-STD-2204 (FDDI), or Buses / FDDI / MIL-STD-2204 (SafeNet)

Fibre Channel FC-AE Buses / Fibre Channel [Fiber Channel]

CANaerospace/AGATE databus is a 1Mbps two-wire bus used to interconnect sensors and navigation systems for General Aviation [GA].
The AGATE databus is based on the CANbus.
AGATE [Advanced General Aviation Experiments] is an alliance [consortium] of Government [NASA] and Industry.

Additional Avionic buses: H009 bus, 16PP362A Weapons bus, EN 3910
- Fibre Optic Digital Time Division, Command / Response Multiplex Data Bus, STANAG 3838 AVS

Avionics Standards Links

US Department Of Defense, 'DOD Index of Specifications and Standards' [http://multisearch.dtic.mil/]
UK Defense Standardization 'DSTAN'
Avionic Systems Standardization Committee 'ASCC' [www.assconline.co.uk]
American Institute of Aeronautics and Astronautics, Inc. "AIAA"
Air Transport Association of America, Inc. "ATA"
ARINC 'Aeronautical Radio INC'
Society of Automotive Engineers 'SAE'
IEEE 'Institute of Electrical and Electronic Engineers' .... ANSI {American National Standards Institute}
NASA 'National Aeronautics and Space Administration' ... and NASA; Aero-Space Technology Enterprise [www.aeronautics.nasa.gov]
FAR; 'Federal Aviation Regulations' [www.airweb.faa.gov], and FAR Bus topics

JIAWG: Joint Integrated Avionics Working Group



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