ARINC 818
Encyclopedia
ARINC 818: Avionics Digital Video Bus (ADVB) is a video interface and protocol standard developed for high bandwidth, low latency, uncompressed digital video transmission in avionics
systems. The standard, which was released in January 2007, has been advanced by ARINC
and the aerospace community to meet the stringent needs of high performance digital video.
, an ever-increasing amount of information is supplied in the form of images, this information passes through a complex video system before reaching cockpit displays
. Video systems include: infrared
and other wavelength sensors, optical cameras, radar
, flight recorder
s, map/chart systems, synthetic vision
, image fusion
systems, heads-up displays
(HUD) and heads-down primary flight
and multifunction
displays, video concentrators, and other subsystems. Video systems are used for taxi and take-off assist, cargo loading, navigation
, target tracking, collision avoidance, and other critical functions.
ARINC 818/ADVB is a Fibre Channel
(FC) protocol which builds on FC-AV (Fibre Channel Audio Video, defined in ANSI INCITS 356-2002), which was used extensively on video systems in the F-18 and the C-130AMP
. Although FC-AV has been used on numerous programs, each implementation has been unique. ARINC 818 provides an opportunity to standardize high speed video systems.
serial protocol for transmission of video, audio, and data. The protocol is packetized, but is video-centric and very flexible, supporting an array of complex video functions including the multiplexing of multiple video streams on a single link or the transmission of a single stream over a dual link. Four different classes of video are defined, from simple asynchronous to stringent pixel synchronous systems.
The start of an ADVB frame is signaled by a SOFx 4-byte Ordered Set and terminated with an EOFx Ordered Set. Every ADVB frame has a standard Fibre Channel header composed of six 32-bit words. These header words pertain to such things as the ADVB frame origin and intended destination and the ADVB frames position within the sequence. The Source ID field (SID) in the ADVB frame header allows video from each sensor to be distinguished from the other sensors.
The “payload” contains either video, video parameters or ancillary data. The payload can vary in size, but is limited to 2112 bytes per ADVB frame. To insure data integrity, all ADVB frames have a 32-bit CRC
calculated for data between the SOFx and the CRC word. The CRC is the same 32-bit polynomial calculation defined for Fibre Channel.
An example of how ARINC 818 transmits color XGA provides a good overview. XGA RGB requires ~141M bytes/s of data transfer (1024 pixels x 3 bytes per pixel x 768 lines x 60 Hz). Adding the protocol overhead and blanking time, a standard link rate of 2.125Gbit/s is required. ARINC 818 “packetizes” video images into Fibre Channel frames. Each FC frame begins with a 4 byte ordered set, called an SOF (Start of Frame), and ends with an EOF (End of Frame), additionally, a 4 byte CRC is included for data integrity. The payload of the first FC frame in a sequence contains embedded header data that accompanies each video image.
Each XGA video line requires 3072 bytes, which exceeds the maximum FC payload length, so each line is divided into two FC frames. Transporting an XGA image requires a “payload” of 1536 FC frames. Additionally, an ADVB header frame is added, making a total of 1537 FC frames. Idle characters are required between FC frames because they are used for synchronization between transmitters and receivers.
Low speed implementations of ARINC 818 (1.0625Gbit/s) can use copper (twinax or STP) or fiber, and high speed implementations (2 Gbit/s+) can use either 850 nm MM fiber (<500m) or 1310 nm SM fiber (up to 10 km). ARINC 818 lends itself to applications that require few conductors (slip ring
s, turrets
), low weight (aerospace), EMI
resistance, or long distance transmission (aerospace, ships).
, which are common in large FPGAs such as the Xilinx Virtex 2 Pro.
ARINC 818 transmitters must assemble valid FC frames, including starting and ending ordered sets, headers, and CRC. This can easily be done with VHDL state machines, and many PLD
SerDes include built in CRC calculations.
The flexibility of ARINC 818 allows for receiver implementations using either full image buffers or just display-line buffers. For either, synchronization issues must be considered at the pixel, line, and frame level.
Line buffer or FIFO based receivers will require that the transmitter adhere to strict line timing requirements of the display. Since the display horizontal scanning
must be precise, the arrival time of lines will also need to be precise. ARINC 818 intends that timing parameters such as these be captured in an ICD specific to the video system.
The authors of ARINC 818 built upon many years of combined experience of using FC to transport different video formats, and key implementation details are included in the specification, including examples of common analog formats.
Avionics
Avionics are electronic systems used on aircraft, artificial satellites and spacecraft.Avionic systems include communications, navigation, the display and management of multiple systems and the hundreds of systems that are fitted to aircraft to meet individual roles...
systems. The standard, which was released in January 2007, has been advanced by ARINC
ARINC
Aeronautical Radio, Incorporated , established in 1929, is a major provider of transport communications and systems engineering solutions for eight industries: aviation, airports, defense, government, healthcare, networks, security, and transportation...
and the aerospace community to meet the stringent needs of high performance digital video.
Background
In aircraftAircraft
An aircraft is a vehicle that is able to fly by gaining support from the air, or, in general, the atmosphere of a planet. An aircraft counters the force of gravity by using either static lift or by using the dynamic lift of an airfoil, or in a few cases the downward thrust from jet engines.Although...
, an ever-increasing amount of information is supplied in the form of images, this information passes through a complex video system before reaching cockpit displays
Cockpit display system
The Cockpit display systems provides the visible portion of the Human Machine Interface by which aircrew manage the modern Glass cockpit and thus interface with the aircraft avionics.-History:...
. Video systems include: infrared
Infrared
Infrared light is electromagnetic radiation with a wavelength longer than that of visible light, measured from the nominal edge of visible red light at 0.74 micrometres , and extending conventionally to 300 µm...
and other wavelength sensors, optical cameras, radar
Radar
Radar is an object-detection system which uses radio waves to determine the range, altitude, direction, or speed of objects. It can be used to detect aircraft, ships, spacecraft, guided missiles, motor vehicles, weather formations, and terrain. The radar dish or antenna transmits pulses of radio...
, flight recorder
Flight recorder
A flight recorder is an electronic recording device placed in an aircraft for the purpose of facilitating the investigation of an aircraft accident or incident. For this reason, flight recorders are required to be capable of surviving the conditions likely to be encountered in a severe aircraft...
s, map/chart systems, synthetic vision
Synthetic vision
A Synthetic Vision System is a computer-mediated reality system for aerial vehicles, that uses 3D to provide pilots with clear and intuitive means of understanding their flying environment....
, image fusion
Image fusion
In computer vision, Multisensor Image fusion is the process of combining relevant information from two or more images into a single image. The resulting image will be more informative than any of the input images....
systems, heads-up displays
Head-Up Display
A head-up display or heads-up display is any transparent display that presents data without requiring users to look away from their usual viewpoints...
(HUD) and heads-down primary flight
Primary flight display
A primary flight display or PFD is a modern aircraft instrument dedicated to flight information. Much like multi-function displays, primary flight displays are built around an LCD or CRT display device...
and multifunction
Multi-function display
A Multi-function display is a small screen in an aircraft surrounded by multiple buttons that can be used to display information to the pilot in numerous configurable ways. Often an MFD will be used in concert with a Primary Flight Display. MFDs are part of the digital era of modern planes or...
displays, video concentrators, and other subsystems. Video systems are used for taxi and take-off assist, cargo loading, navigation
Air navigation
The basic principles of air navigation are identical to general navigation, which includes the process of planning, recording, and controlling the movement of a craft from one place to another....
, target tracking, collision avoidance, and other critical functions.
ARINC 818/ADVB is a Fibre Channel
Fibre Channel
Fibre Channel, or FC, is a gigabit-speed network technology primarily used for storage networking. Fibre Channel is standardized in the T11 Technical Committee of the InterNational Committee for Information Technology Standards , an American National Standards Institute –accredited standards...
(FC) protocol which builds on FC-AV (Fibre Channel Audio Video, defined in ANSI INCITS 356-2002), which was used extensively on video systems in the F-18 and the C-130AMP
C-130 Hercules
The Lockheed C-130 Hercules is a four-engine turboprop military transport aircraft designed and built originally by Lockheed, now Lockheed Martin. Capable of using unprepared runways for takeoffs and landings, the C-130 was originally designed as a troop, medical evacuation, and cargo transport...
. Although FC-AV has been used on numerous programs, each implementation has been unique. ARINC 818 provides an opportunity to standardize high speed video systems.
Overview of ARINC 818 Protocol
ARINC 818 is a point-to-point, 8B/10B encoded8B/10B encoding
In telecommunications, 8b/10b is a line code that maps 8-bit symbols to 10-bit symbols to achieve DC-balance and bounded disparity, and yet provide enough state changes to allow reasonable clock recovery. This means that the difference between the count of 1s and 0s in a string of at least 20 bits...
serial protocol for transmission of video, audio, and data. The protocol is packetized, but is video-centric and very flexible, supporting an array of complex video functions including the multiplexing of multiple video streams on a single link or the transmission of a single stream over a dual link. Four different classes of video are defined, from simple asynchronous to stringent pixel synchronous systems.
ADVB Packet Structure
The ADVB frame is the basic transport mechanism for ARINC 818. It is important to refer to these packets as “ADVB frames” rather than simply “frames” to eliminate potential confusion with video frames.The start of an ADVB frame is signaled by a SOFx 4-byte Ordered Set and terminated with an EOFx Ordered Set. Every ADVB frame has a standard Fibre Channel header composed of six 32-bit words. These header words pertain to such things as the ADVB frame origin and intended destination and the ADVB frames position within the sequence. The Source ID field (SID) in the ADVB frame header allows video from each sensor to be distinguished from the other sensors.
The “payload” contains either video, video parameters or ancillary data. The payload can vary in size, but is limited to 2112 bytes per ADVB frame. To insure data integrity, all ADVB frames have a 32-bit CRC
Cyclic redundancy check
A cyclic redundancy check is an error-detecting code commonly used in digital networks and storage devices to detect accidental changes to raw data...
calculated for data between the SOFx and the CRC word. The CRC is the same 32-bit polynomial calculation defined for Fibre Channel.
ADVB Container Structure
The ARINC 818 specification defines a “container” as a set of ADVB frames used to transport video. In other words, a video image and data is encapsulated into a “container” that spans many ADVB frames. The “payload” of each ADVB frame contains either data or video. Within a container, ARINC 818 defines Objects that contain certain types of data. That is, certain ADVB frames within the container are part of an Object.An example of how ARINC 818 transmits color XGA provides a good overview. XGA RGB requires ~141M bytes/s of data transfer (1024 pixels x 3 bytes per pixel x 768 lines x 60 Hz). Adding the protocol overhead and blanking time, a standard link rate of 2.125Gbit/s is required. ARINC 818 “packetizes” video images into Fibre Channel frames. Each FC frame begins with a 4 byte ordered set, called an SOF (Start of Frame), and ends with an EOF (End of Frame), additionally, a 4 byte CRC is included for data integrity. The payload of the first FC frame in a sequence contains embedded header data that accompanies each video image.
Each XGA video line requires 3072 bytes, which exceeds the maximum FC payload length, so each line is divided into two FC frames. Transporting an XGA image requires a “payload” of 1536 FC frames. Additionally, an ADVB header frame is added, making a total of 1537 FC frames. Idle characters are required between FC frames because they are used for synchronization between transmitters and receivers.
Applications
Although ARINC 818 was developed specifically for avionics applications, the protocol is already being used in sensor fusion applications where multiple sensor outputs are multiplexed onto a single high speed link.Low speed implementations of ARINC 818 (1.0625Gbit/s) can use copper (twinax or STP) or fiber, and high speed implementations (2 Gbit/s+) can use either 850 nm MM fiber (<500m) or 1310 nm SM fiber (up to 10 km). ARINC 818 lends itself to applications that require few conductors (slip ring
Slip ring
A slip ring is a method of making an electrical connection through a rotating assembly. Slip rings, also called rotary electrical interfaces, rotating electrical connectors, collectors, swivels, or electrical rotary joints, are commonly found in electric motors, electrical generators for AC...
s, turrets
Gun turret
A gun turret is a weapon mount that protects the crew or mechanism of a projectile-firing weapon and at the same time lets the weapon be aimed and fired in many directions.The turret is also a rotating weapon platform...
), low weight (aerospace), EMI
Electromagnetic interference
Electromagnetic interference is disturbance that affects an electrical circuit due to either electromagnetic induction or electromagnetic radiation emitted from an external source. The disturbance may interrupt, obstruct, or otherwise degrade or limit the effective performance of the circuit...
resistance, or long distance transmission (aerospace, ships).
Flexibility vs. Interoperability
ARINC 818 is flexible and can accommodate many types of video and data applications. It is the intention of the standard that all implementation be accompanied by a small interface control document (ICD) that defines key parameters of the header such as: link speed, video resolution, color scheme, size of ancillary data, timing classification, or bit-packing schemes. Interoperability is only guaranteed among equipment built to the same ICD.Implementation Considerations
ARINC 818 uses a FC physical layer that can be constructed from any FC compatible 8B/10B SerDesSerDes
A Serializer/Deserializer is a pair of functional blocks commonly used in high speed communications to compensate for limited input/output. These blocks convert data between serial data and parallel interfaces in each direction...
, which are common in large FPGAs such as the Xilinx Virtex 2 Pro.
ARINC 818 transmitters must assemble valid FC frames, including starting and ending ordered sets, headers, and CRC. This can easily be done with VHDL state machines, and many PLD
Programmable logic device
A programmable logic device or PLD is an electronic component used to build reconfigurable digital circuits. Unlike a logic gate, which has a fixed function, a PLD has an undefined function at the time of manufacture...
SerDes include built in CRC calculations.
The flexibility of ARINC 818 allows for receiver implementations using either full image buffers or just display-line buffers. For either, synchronization issues must be considered at the pixel, line, and frame level.
Line buffer or FIFO based receivers will require that the transmitter adhere to strict line timing requirements of the display. Since the display horizontal scanning
Horizontal scan rate
Horizontal scan rate, or horizontal frequency, usually expressed in kilohertz, is the frequency at which a CRT moves the electron beam from the left side of the display to the right and back, and therefore describes the number of horizontal lines displayed per second...
must be precise, the arrival time of lines will also need to be precise. ARINC 818 intends that timing parameters such as these be captured in an ICD specific to the video system.
The authors of ARINC 818 built upon many years of combined experience of using FC to transport different video formats, and key implementation details are included in the specification, including examples of common analog formats.
See also
- Aircraft flight control systemsAircraft flight control systemsA conventional fixed-wing aircraft flight control system consists of flight control surfaces, the respective cockpit controls, connecting linkages, and the necessary operating mechanisms to control an aircraft's direction in flight...
- Fibre Channel 8B/10B encodingFibre Channel 8B/10B encodingThe Fibre Channel FC1 data link layer implements the 8b/10b encoding and decoding of signals.The Fibre Channel 8B/10B coding scheme is also used in other telecommunications systems. Data is expanded using an algorithm that creates one of two possible 10-bit output values for each input 8-bit value...
- Fibre Channel network protocolsFibre Channel network protocolsCommunication between devices in a fibre channel network uses different elements of the Fibre Channel standards. The following sections introduce the main concepts and show how a combination of primitives and frames is required....
- Integrated Modular AvionicsIntegrated Modular AvionicsIntegrated modular avionics represent real-time computer network airborne systems. This network consists of a number of computing modules capable of supporting numerous applications of differing criticality levels....