Aeronautical Radio INC 429 (ARINC 429) is the industry standard avionics data bus used in high-end transport and commercial aircraft, also known as Mark 33 Digital Information Transfer System (DITS), and the ARINC 429 sets the standard for data transfer. The specification is under copyright and provides for the interchange of line replaceable units in transport and commercial aircraft. There are no requirements for the manufacturers of avionic equipment to comply with the ARINC429 standard.
ARINC
ARINC develops avionic standards and specifications for private manufacturers both foreign and domestic. Its specifications are used for packing and mounting, data communications and computer languages in the avionics industry. ARINC429 or Mark 33 DITS is defined under their specifications, and ARINC reporting offers best practice guides, maintenance and support practices. The ARINC429 defines the electrical, data word structure and protocol for bus communication. It covers both hardware and data formats for bus transmission through point to point architecture for reliable data transfer.
Interference Reduction
The A429 meets all requirements set by RTCA DO-160. It reduces electromagnet interference to a minimum with its physical and electrical and protocol capabilities, and it reduces EMI transmissions from the cable. It enhances transmissions of on-board radios, transmission cables and other units. Twisted cable pairs with shielding operate using a bipolar (return to zero) transmission defining voltage and fall times. Return to Zero modulation eliminates the need for external clocking devices.
Data Word Formats
Using a point to point format the A429 protocol can transmit to up to 20 receivers. The transmission is constant with either data or a null. Binary, binary decimal or alphanumeric encoded messages are usually one data word, but it is not limited to one-word transmission. There are five primary fields to the make of the ARINC429 32-bit words. They are parity, sign and status matrix, data, source and destination identifier and label. All data is transmitted at 32 bits or with added zeros for unused bits.
The A429 is a self-synchronizing, self-clocking data bus protocol. The 32-bit single data words transmit at kilobits to the bus monitors. The transmissions are constant and with either the data or a null signal or state. It’s used an alternative to the MIL-STD-1553.
