Since 70th years and still remains the most common ARINC 429 standard for construction of avionics. Designed by one of the largest corporations in the development of standards for aviation in the US Aeronautical Radio Inc [38; 71; 77].
The basic principle of information transfer is that the power-source information it gives to all who need it. Information appears consistently by transmitter. It is possible the connection of the "star" when receivers combined separate line of communication with the transmitter (Fig. 18) or may use bus topology of communications where one transmitter gives information and up to 20 connected in parallel receivers get the information that they need (Fig. 19). In addition, the organization can multiplex connection (Fig. 20).
Fig. 18. The connection of the "star"
At the physical level of the communication channel for connection using two woven and well shielded wires. The length of the connecting wires standard unpredictable, but network equipment allows for operation of cable length up to 90 m. Considering the fact that the vast majority of wired connections on the PC does not exceed 55 m. ARINC 429 can be used to organize the link between any LRU.
Fig. 19. Connect one source of information
Fig. 20. Multiplexed communication organization
Information transfer in the opposite direction unpredictable. If necessary for this purpose used a separate communication line (Fig. 21). According to this for organization of duplex connection used two lines DDB.
Fig. 21. Organization of the duplex communication
All information receivers are connected to a single pair of wires and each of them selects in the information that is transmitted and what needed. Transferring asynchronously means that unit source sends information when it is ready for transfer. The receiver should be ready to accept this information, or at least place it in the internal memory to not lose it. Signals about reported of receiving information is not used. Since the data is transmitted cyclically, then made the wrong message can get some other time.
For transmission of digital information using two-level state amplitude relative to zero. Low level corresponds to a logic zero "0", and the high - logical unit "1" (Fig. 22). Zero condition reflects a pause between the transmitted bits.
Fig. 22. Two-state amplitude relative to the zero value.