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FlexRay - Topology | Cypress Semiconductor

FlexRay - Topology

 Background |  Overview |  Features |  In-car Communication Protocol |  Target applications |  Data transfer method |  Difference with CAN |  Internal configuration of a node |  Electronic signals |  Bus Guardian |  Topology |  Segment configuration |  Protocol |  Status transition |  Error control |

FlexRay ASSP

There are two types of topology, bus type and star type, and each of them has single-channel type and dual-channel type.

  • Bus type characteristic:

    Similar to CAN, it is a passive medium, a lot of experience is available with this technology, and it is cost efficient
  • Star type characteristic:

    Because its connection is point-to-point, it is for high-speed data rate. It is also easy to reduce failures such as a short-circuit of bus.
 FlexRay topology type and features

FlexRay topology type and features

  • Single channel characteristics:

    Similar to the bus type and CAN, it has a few harnesses, but a lot of experience is available. Also, because of the single connection, it is cost effective.
  • Dual channel characteristics:

    By making redundant configuration, it is fault tolerant.

FlexRay supports three types of topology, bus-type, star-type, and hybrid-type that is a combination of bus-type and star-type.

The minimum number of system nodes is two.

The minimum fault tolerant system nodes is three nodes.

Although the minimum number of nodes in configuration is two, the number of synchronized nodes should be three considering the fault tolerance.

Point to Point Connection

Most standard network topology

Basic configuration against the more complex topology configuration

Linear Passive Bus

When three nodes are connected on a bus, the bus becomes a linear passive bus

Passive Star

All nodes on a linear passive bus are connected to a single point.

Active Star

Inter-node connection with an active star.

Cascade Active Star

Active start allows cascade connection.

The mutual point-to-point connection is allowed.


Individual connections. Can be combined among the connections within each oval.


The example of terminal value for ECU (node) is shown below.

Example of ECU (node) resistance

Terminal resistance
Terminal resistance value

- Note -

Some parts of this site show only the outlines of the actual FlexRay standards to make them easily understood.