I want to know the different aircraft systems (LRUs) using ARINC429 protocol.
Why is it used instead of the ARINC 629 ?
How is it different from the different ARINC protocols like 629 and AFDX(664)?
On modern aircraft all equipments that needs to communicate to each other in binary format may use ARINC 429 protocol. For instance all fly by wires computers on Airbus 320, 330, 340 use arinc 429 protocol.
Nowadays other protocols do exist too such as arinc 629 protocol or fiber optic protocols etc.
As a summary all aircraft systems that need to transmit and receive binary data may use 429 protocol, but other digital protocols are possible.
However a standardized LRU that doesn’t use ARINC 429 protocol is the FDR ( flight data recorder), because the data that it receives is already sequentially ordered, the label is not transmitted with the data value
On the following website starting page 43 you find all the possible equipment that may use A429
Also in the same document starting page 13 you have the list of the parameters that may be transmitted on A429
Hope this added information is helpful
Many LRUs have capabilities to send and receive on one or more of the protocols you have specified. Depending on the age and necessity/capabilities of the system, they might have interfaces for one or all. There are also CAN bus standards and others. Each protocol offers a similar approach to data transfer with unique capabilities for each, for example AFDX can implement redundancy and broadcast-like abilities through Virtual Links while A429, while older, is in wider use. If you could refine you question so it is not so broad, I'm sure I could give you a more detailed answer.