Bmw flexray how fast is it

In the previous article we looked at CAN Controller Area Network Bus communication, however, with safety-critical Drive-by-Wire systems, a higher data transfer rate and improved error detection is required.

These act to reduce the effects of external interference on the differential voltage between both wires. Data transfer speeds can be up to 10 times faster than CAN bus, operating at speeds up to 1 Mbit per second. Although the normal data transfer speed for CAN is Kbits per second, it has the capability to transmit at speeds of 1 Mbit per second. FlexRay can support network redundancy, or dual channels. This ensures greater fault tolerance as well as increased bandwidth for additional data transfer.

However, this additional network is rarely implemented. This ensures signal reflections are reduced, which is an issue with such high data transfer speeds. CAN bus messages are subject to arbitration to ensure messages of higher priority have access to the network first.

FlexRay supports both Event triggered messaging and Deterministic messaging which allows for high data rates and guarantees message delivery when required. Each node or module has a predetermined time slot to transmit its data. This creates a differential voltage of It provided a new and quickly adapting damping system.

Each ECU has an integrated independent clock. The time deviation from the reference clock may not exceed 0. As such, when ECU-s is the transmitter and ECU-r is the receiver, cycles of the transmitter always will result in to cycles at the receiver.

The clocks are synchronized continuously to ensure that no problems are caused by this. The bus is always described by one ECU only. Every bit which is to be sent to the bus must be held for eight time cycles. The receiver keeps a buffer for the last five samples and it uses most of the last five samples as the input signal.

The value of a bit is found near the 8-bit region. The errors are shifted into the extreme cycles, and the clock is synchronized often enough, so that the deviation is only small. The deviation is smaller than one cycle per cycles.

During the transmission, the clock is synchronized more frequently, i. The entire communication takes place with the aid of frames. The clocks are resynchronized when the signal changes from 1 to 0, i. The clock is synchronized when the transmission starts. When synchronization of the selected signal has been completed, small transmission errors can change the synchronization by not more than one cycle. As there are max.