More about ARINC 429
The ARINC 429 Specification establishes the specifications for digital data transmission between commercial aircraft avionics systems. The Mark 33 DITS Specification is another name for ARINC 429. On the Mark 33 Digital Information Transfer System (DITS) bus, signal levels, timing, and protocol features are provided for design implementation and data transmission simplicity. ARINC 429 is a copywritten specification produced by a private company to interchange and interoperability line replaceable units (LRUs) in commercial planes. Manufacturers of avionics equipment are not required to follow the ARINC 429 Specification, although building avionics systems following the design principles ensure compatibility between functional units across manufacturers.
Here are some characteristics and specifications of ARINC 429
Characteristics define the shape, fit, and function of avionics equipment. These documents are particular to a piece of equipment and describe how it will function. The ARINC 500 Series of Attributes documents are for older analog avionics equipment, and the ARINC 700 Series documents are for more modern digital avionics equipment and are often digital copies of the analog specifications. The 400 Series papers are design and support documents for the 500 Series avionics equipment. General design and support documentation for the 700 Series avionics equipment.
- ARINC Requirements
Specifications are used to establish the parameters of a project.
- Packaging and installation of avionics equipment
- Communication protocols for data
- High-level programming languages
The ARINC429 Specification, Mark 33 Digital Information Transfer System is a document in the Specification category.
The ARINC 429 Specification defines how commercial aircraft’s avionics equipment and systems interact. The standard specifies the electrical properties, word formats, and protocol required for bus communication. The Mark 33 Digital Information Transfer System bus is used by ARINC 429. It’s a simplex, twisted shielded pair data bus.
ARINC 429 specifies both the hardware and data formats necessary for bus transmission. One twisted wire pair connects a single transmitter (or source) to one to twenty receivers (or sinks). Simplex communication allows data to be transferred in just one way, whereas bi-directional communication necessitates two channels or buses. Most make the process easier units, or LRUs, are set up in a star or bus-drop topology. Several transmitters and receivers may be included in each LRU, communicating on a separate frequency.
This minimal architecture, practically point-to-point wiring, ensures that data is sent reliably.
A transmitter may ‘speak only’ to a limited number of receivers on the bus, up to 20 on a single wire pair. Each receiver constantly checks for its relevant data but fails to acknowledge receipt.
When huge volumes of data are exchanged, a transmitter may request acknowledgment from the receiver. Instead of a hardwired handshake, this handshaking is done via a specific phrase style. When this two-way communication style is required, two twisted pairs, one for each direction, are required to transport information back and forth. At least four nulls or zero voltage bits are used to distinguish sequential words. A separate clock signal isn’t needed because the null gap between words is used. Transmission rates might range from 12.5 kHz to 100 kHz.