ARINC 429 is a developed in the 1970s and introduced in the 1980 data bus standard for commercial aircraft. A distinction is made between a high-speed and low-speed a bus. For a high-speed bus, the maximum data transfer rate is 100 kbit / s, at low speed 12.5 kbit / s
There are other protocols after Arinc standard. ARINC 429 is found in a light variation is also in business and private aircraft again. In military aviation and space flight of the MIL -STD -1553 bus is used instead of the ARINC bus preferably.
In principle, the Serial Interface ARINC -429 with the differential EIA-422 interface comparable. Only take two different levels are defined three ( 10 V, 0 V and -10 V). As individual bits are transmitted, one sees in the representation of the resulting difference signal ( ARINC -429 - timing).
It is characteristic for each bit, that the level for half the time, the voltage of 10 V and then the other half of 0 V ( RZ code ). So there are at each bit synchronization information. An asynchronous interface such as RS -232 needed for comparison for each data word a start and stop bit.
The communication is a one -to -n junction (a transmitter, receiver n ). Due to the high voltage level, the same restrictions on cable length and transmission rate as RS- 232 and RS -422 apply. Therefore also quite moderate transfer rates of either 12.5 ... 14.5 or 100 kilobits / second are defined. In the low-speed mode tolerances are 10% and in the high-speed mode tolerances of 5 % for the transmission rate.
In order not to generate interference signals by the transmission possible, there is a so-called slope control. This means that the rising and falling edges corresponding to the transmission rate run flat as possible. Since there is no start bit, the initial recognition of a 32 bit data word is a pause of at least 4 bits, where there is no signal (Sync gap: minimum 4 bits). Within the 32 bits of data is only a gap of max. 2 bit periods allowed. And at the end of the data word is a gap of at least 4 bit periods is defined again.