FlexRay is an automotive network technology conceived as a replacement for the CAN (Controller Area Network) standard, which cannot support the number of nodes and the sophistication of network-enabled functions that manufacturers want to build into today's vehicles.
FlexRay, however, has enjoyed limited success because systems designers have struggled to deliver reliable communications over extended cable lengths or in complex network topologies. At the root of the difficulties in FlexRay implementation is the phenomenon of asymmetric propagation delay, caused by, among other things, electro-magnetic interference (EMI) and extended cable lengths between nodes. The effect of asymmetric propagation delay is to shrink or expand the length of a bit to the point at which it cannot be decoded correctly at the receiver.
A new bit-reshaping technique implemented in the AS8224 FlexRay transceiver from austriamicrosystems, however, corrects bit timing mismatches, ensuring that asymmetric delays are corrected at a central point in the network, where the effect of the corrections does most to improve network stability.
By using a bit-reshaping capability, systems designers can develop FlexRay networks that benefit from:
For the complete article, including a discussion of the nature of asymmetric delays and how the Bit-Reshaper works to extend topologies, click here, courtesy of Automotive Designline Europe.
- Enhanced and enlarged topologies, including topologies with more than one Active Star
- Longer cable runs
- More reliable operation in harsh conditions, such as the presence of high EMI
- The use of inexpensive unsheathed cable, as used today in CAN networks