Evolution Of Arinc 429

28 November, 2016

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ARINC-429 has been used and is being used on numerous commercial aircraft despite being over 40 year’s old. The following article will ponder upon the complexity of systems employing ARINC 429 and how the ARINC-429 evolved over the years, and is still the most reliable avionics data bus standard.

Arinc-429 In Modern Aircraft

Even after four decades, the ARINC 429 data bus protocol is considered as an important data bus standard given it is used in the avionics systems of the B737, B747, B767, A320, A340, and MD-11 aircraft. Given the reputation of ARINC 429 in the present times, it is evident that it will remain popular in the years to come. Latest aircraft like B777, and A380 are designed with integrated and complex avionics architectures, e.g., the B777 still use ARINC-429 buses to transport sensor data between mission critical systems. Similarly it is also used Navy’s P-8 Poseidon, a military system based on commercial aircraft.

How Avionics Architectures Become Complex

ARINC-429 data bus looks like a simple legacy bus with a single direction communication channel which transmits 32-bit samples with a maximum data rate of 100 Kbits/sec. However, the simplicity of individual data increases the complexity if there are hundreds of data buses present in an aircraft. A maximum of 20 systems can be connected using ARINC-429 using a single pair of cable, but usually only two systems are connected on a single bus, configures as a transmitter and  receiver respectively. Each system that needs to transmit data to other systems will have its own bus connecting it to one or more of those systems. A complex system may need data from multiple sensors in order to make critical decisions and carry out certain actions. This data bus communication must happen with precision and accuracy to avoid any randomness and allow for a deterministic behavior. This type of performance is difficult to achieve due to complex timing and synchronization issues. Even wiring up the complete data bus connections to every system on the aircraft is a big task in itself.

Optimization Using Embedded Systems

ARINC-429 has sustained these complex avionics systems as interface technology moved from PCI to VME bus and on to high data rate systems like VPX and PCI Express. With more and more data channels are being accommodated in cards, higher time resolution, along with programming features is now possible using ARINC-429 data bus standard. Boards have added more memory and I/O and have gotten smaller and smaller e.g., from PC cards to XMC modules. A simple example is GE Intelligent Platforms RAR-XMC is a latest ARINC 429 embedded system with a four-lane XMC card that provides a total of 32 channels, and 16 of these channels can be programmed to act as transmitters or receivers with a 64-bit time tag resolution.

Conclusion

ARINC-429 is very simple legacy bus, but the integration of multiple sensors and monitoring systems increases the complexity of the avionics architecture due to complex wiring schemes and extensive interdependencies. This complexity can be managed using ARINC-429 with advanced embedded interfaces which provide both flexibility and usability from emulation to real time testing in very complex avionics systems. 

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