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FlexRay - Segment configuration | Cypress Semiconductor

FlexRay - Segment configuration

 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

FlexRay segment configuration consists of the static segment with the fixed time trigger method and the dynamic segment with the flexible time trigger method.
In addition, there are symbol window that tests the bus guardian operations, and the network idle time segment used for clock correction. Features of each segment are listed below.

FlexRay segment features

  Features Slot length/
data length
Priorities Bus Guardian
Static Segment Sends and receives messages with time triggers Fixed length Fixed by Fixed TDMA Because the timing for sending is fixed, it is protected by BG.
Dynamic Segment Sends and receives messages with event triggers Variable length Sending in ascending order of ID Because the timing of sending is undetermined, it cannot be protected by BG.
Confirms the normality of BG. Fixed length - BG can disable sending.
Idle Time
Global synchronous processing period Variable length - -

The symbol window is not used unless the bus guardian is used.

The FlexRay segment configuration can be designed in the following patterns depending on the system specifications.

Segment configuration

The static segment and NT segment are required for configuration.

Communication cycles and segments/slot configuration

Because it enables the data transfer with redundancy, the data transfer for which high reliability is required is available.

The frequency of a cycle is from 0 to 63. A cycle consist of four segments, static segment, dynamic segment, symbol window, and network idle time.

The static segment consists of integral multiples of fixed-length static slots, and it sends and receives static frames to and from the static slots.
The dynamic segment consists of fixed-length mini slots. By changing the number of mini slots, the dynamic slot can be variable length.

 Segment and slot configuration


A slot consists of the idle time and a frame that sends and receives data.

- Note -

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