Moreover, FlexRay allows both synchronous (real-time) and asynchronous data transfer to meet the demand for various systems in vehicles.
FlexRay uses two methods for granting bus access to nodes
• TDMA (Time Division Multiple Access)
The TDMA method uses a communication schedule which is split into time slots. Each FlexRay node has one or more slots assigned in which it is granted access to the bus .The communication schedule is repeated periodically by all nodes . [14]
• FTDMA (Flexible Time Division Multiple Access)
The FTDMA method is used to implement a dynamic segment which reserves a specific slot in the communication cycle that can be used by any node to transmit messages in a non-deterministic manner.
FlexRay uses differential signal transmission and NRZ encoding with Two communication lines: Bus Plus (BP) and Bus Minus (BM). The physical layer defines four bus levels :
• Dominant – differential voltage not equal to 0 V (Data_1, Data_0).
• Recessive – differential voltage of 0V (Idle & low power).