DO-254 IP : ARINC429

ARINC 429 is the technical standard for the avionics data bus used on most higher-end commercial and transport aircraft. It defines the physical and electrical interfaces of a two-wire data bus and a data protocol to support an aircraft's avionics local area network. The support of a Label mechanism is provided as part of the ARINC 429 specification, for various equipment types. Each aircraft will contain a number of different systems, such as flight management computers, inertial reference systems, air data computers, radar altimeters, radios, and GPS sensors. For each type of equipment, a set of standard parameters is defined, which is common across all manufacturers and models.
ARINC 429 is a two-wire, point-to-point data bus that is application-specific for commercial and transport aircraft. The connection wires are twisted pairs. Words are 32 bits in length and most messages consist of a single data word. The specification defines the electrical standard and data characteristics and protocols. ARINC 429 uses a unidirectional data bus standard (Tx and Rx are on separate ports) known as the Mark 33 Digital Information Transfer System (DITS). Messages are transmitted at 12.5, 50 (optional), or 100 kbps to other system elements that are monitoring the bus messages. The transmitter is always transmitting either 32-bit data words or the Null state.